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Jie Deng

2020-Sep-03 05:34 UTC

[PATCH] i2c: virtio: add a virtio i2c frontend driver

Add an I2C bus driver for virtio para-virtualization.

The controller can be emulated by the backend driver in
any device model software by following the virtio protocol.

This driver communicates with the backend driver through a
virtio I2C message structure which includes following parts:

- Header: i2c_msg addr, flags, len.
- Data buffer: the pointer to the i2c msg data.
- Status: the processing result from the backend.

People may implement different backend drivers to emulate
different controllers according to their needs. A backend
example can be found in the device model of the open source
project ACRN. For more information, please refer to
https://projectacrn.org.

The virtio device ID 34 is used for this I2C adpter since IDs
before 34 have been reserved by other virtio devices.

Co-developed-by: Conghui Chen <conghui.chen at intel.com>
Signed-off-by: Conghui Chen <conghui.chen at intel.com>
Signed-off-by: Jie Deng <jie.deng at intel.com>
Reviewed-by: Shuo Liu <shuo.a.liu at intel.com>
Reviewed-by: Andy Shevchenko <andriy.shevchenko at linux.intel.com>
---
 drivers/i2c/busses/Kconfig      |  11 ++
 drivers/i2c/busses/Makefile     |   3 +
 drivers/i2c/busses/i2c-virtio.c | 276 ++++++++++++++++++++++++++++++++++++++++
 include/uapi/linux/virtio_ids.h |   1 +
 4 files changed, 291 insertions(+)
 create mode 100644 drivers/i2c/busses/i2c-virtio.c

diff --git a/drivers/i2c/busses/Kconfig b/drivers/i2c/busses/Kconfig
index 293e7a0..70c8e30 100644
--- a/drivers/i2c/busses/Kconfig
+++ b/drivers/i2c/busses/Kconfig
@@ -21,6 +21,17 @@ config I2C_ALI1535
 	  This driver can also be built as a module.  If so, the module
 	  will be called i2c-ali1535.
 
+config I2C_VIRTIO
+	tristate "Virtio I2C Adapter"
+	depends on VIRTIO
+	help
+	  If you say yes to this option, support will be included for the virtio
+	  i2c adapter driver. The hardware can be emulated by any device model
+	  software according to the virtio protocol.
+
+	  This driver can also be built as a module. If so, the module
+	  will be called i2c-virtio.
+
 config I2C_ALI1563
 	tristate "ALI 1563"
 	depends on PCI
diff --git a/drivers/i2c/busses/Makefile b/drivers/i2c/busses/Makefile
index 19aff0e..821acfa 100644
--- a/drivers/i2c/busses/Makefile
+++ b/drivers/i2c/busses/Makefile
@@ -6,6 +6,9 @@
 # ACPI drivers
 obj-$(CONFIG_I2C_SCMI)		+= i2c-scmi.o
 
+# VIRTIO I2C host controller driver
+obj-$(CONFIG_I2C_VIRTIO)	+= i2c-virtio.o
+
 # PC SMBus host controller drivers
 obj-$(CONFIG_I2C_ALI1535)	+= i2c-ali1535.o
 obj-$(CONFIG_I2C_ALI1563)	+= i2c-ali1563.o
diff --git a/drivers/i2c/busses/i2c-virtio.c b/drivers/i2c/busses/i2c-virtio.c
new file mode 100644
index 0000000..47f9fd1
--- /dev/null
+++ b/drivers/i2c/busses/i2c-virtio.c
@@ -0,0 +1,276 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * Virtio I2C Bus Driver
+ *
+ * Copyright (c) 2020 Intel Corporation. All rights reserved.
+ */
+
+#include <linux/acpi.h>
+#include <linux/completion.h>
+#include <linux/err.h>
+#include <linux/i2c.h>
+#include <linux/io.h>
+#include <linux/jiffies.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/platform_device.h>
+#include <linux/wait.h>
+
+#include <linux/virtio.h>
+#include <linux/virtio_ids.h>
+#include <linux/virtio_config.h>
+
+#define VIRTIO_I2C_MSG_OK	0
+#define VIRTIO_I2C_MSG_ERR	1
+
+/**
+ * struct virtio_i2c_hdr - the virtio I2C message header structure
+ * @addr: i2c_msg addr, the slave address
+ * @flags: i2c_msg flags
+ * @len: i2c_msg len
+ */
+struct virtio_i2c_hdr {
+	__virtio16 addr;
+	__virtio16 flags;
+	__virtio16 len;
+} __packed;
+
+/**
+ * struct virtio_i2c_msg - the virtio I2C message structure
+ * @hdr: the virtio I2C message header
+ * @buf: virtio I2C message data buffer
+ * @status: the processing result from the backend
+ */
+struct virtio_i2c_msg {
+	struct virtio_i2c_hdr hdr;
+	char *buf;
+	u8 status;
+};
+
+/**
+ * struct virtio_i2c - virtio I2C data
+ * @vdev: virtio device for this controller
+ * @completion: completion of virtio I2C message
+ * @adap: I2C adapter for this controller
+ * @i2c_lock: lock for virtqueue processing
+ * @vq: the virtio virtqueue for communication
+ */
+struct virtio_i2c {
+	struct virtio_device *vdev;
+	struct completion completion;
+	struct i2c_adapter adap;
+	struct mutex i2c_lock;
+	struct virtqueue *vq;
+};
+
+static void virtio_i2c_msg_done(struct virtqueue *vq)
+{
+	struct virtio_i2c *vi = vq->vdev->priv;
+
+	complete(&vi->completion);
+}
+
+static int virtio_i2c_add_msg(struct virtqueue *vq,
+			      struct virtio_i2c_msg *vmsg,
+			      struct i2c_msg *msg)
+{
+	struct scatterlist *sgs[3], hdr, bout, bin, status;
+	int outcnt = 0, incnt = 0;
+
+	if (!msg->len)
+		return -EINVAL;
+
+	vmsg->hdr.addr = msg->addr;
+	vmsg->hdr.flags = msg->flags;
+	vmsg->hdr.len = msg->len;
+
+	vmsg->buf = kzalloc(vmsg->hdr.len, GFP_KERNEL);
+	if (!vmsg->buf)
+		return -ENOMEM;
+
+	sg_init_one(&hdr, &vmsg->hdr, sizeof(struct virtio_i2c_hdr));
+	sgs[outcnt++] = &hdr;
+	if (vmsg->hdr.flags & I2C_M_RD) {
+		sg_init_one(&bin, vmsg->buf, msg->len);
+		sgs[outcnt + incnt++] = &bin;
+	} else {
+		memcpy(vmsg->buf, msg->buf, msg->len);
+		sg_init_one(&bout, vmsg->buf, msg->len);
+		sgs[outcnt++] = &bout;
+	}
+	sg_init_one(&status, &vmsg->status, sizeof(vmsg->status));
+	sgs[outcnt + incnt++] = &status;
+
+	return virtqueue_add_sgs(vq, sgs, outcnt, incnt, vmsg, GFP_KERNEL);
+}
+
+static int virtio_i2c_xfer(struct i2c_adapter *adap, struct i2c_msg *msgs, int
num)
+{
+	struct virtio_i2c *vi = i2c_get_adapdata(adap);
+	struct virtio_i2c_msg *vmsg_o, *vmsg_i;
+	struct virtqueue *vq = vi->vq;
+	unsigned long time_left;
+	int len, i, ret = 0;
+
+	vmsg_o = kzalloc(sizeof(*vmsg_o), GFP_KERNEL);
+	if (!vmsg_o)
+		return -ENOMEM;
+
+	mutex_lock(&vi->i2c_lock);
+	vmsg_o->buf = NULL;
+	for (i = 0; i < num; i++) {
+		ret = virtio_i2c_add_msg(vq, vmsg_o, &msgs[i]);
+		if (ret) {
+			dev_err(&adap->dev, "failed to add msg[%d] to
virtqueue.\n", i);
+			goto err_unlock_free;
+		}
+
+		virtqueue_kick(vq);
+
+		time_left = wait_for_completion_timeout(&vi->completion,
adap->timeout);
+		if (!time_left) {
+			dev_err(&adap->dev, "msg[%d]: addr=0x%x timeout.\n", i,
msgs[i].addr);
+			ret = i;
+			goto err_unlock_free;
+		}
+
+		vmsg_i = (struct virtio_i2c_msg *)virtqueue_get_buf(vq, &len);
+		if (vmsg_i) {
+			/* vmsg_i should point to the same address with vmsg_o */
+			if (vmsg_i != vmsg_o) {
+				dev_err(&adap->dev, "msg[%d]: addr=0x%x virtqueue
error.\n",
+					i, vmsg_i->hdr.addr);
+				ret = i;
+				goto err_unlock_free;
+			}
+			if (vmsg_i->status != VIRTIO_I2C_MSG_OK) {
+				dev_err(&adap->dev, "msg[%d]: addr=0x%x error=%d.\n",
+					i, vmsg_i->hdr.addr, vmsg_i->status);
+				ret = i;
+				goto err_unlock_free;
+			}
+			if ((vmsg_i->hdr.flags & I2C_M_RD) && vmsg_i->hdr.len)
+				memcpy(msgs[i].buf, vmsg_i->buf, vmsg_i->hdr.len);
+
+			kfree(vmsg_i->buf);
+			vmsg_i->buf = NULL;
+		}
+		reinit_completion(&vi->completion);
+	}
+	if (i == num)
+		ret = num;
+
+err_unlock_free:
+	mutex_unlock(&vi->i2c_lock);
+	kfree(vmsg_o->buf);
+	kfree(vmsg_o);
+	return ret;
+}
+
+static void virtio_i2c_del_vqs(struct virtio_device *vdev)
+{
+	vdev->config->reset(vdev);
+	vdev->config->del_vqs(vdev);
+}
+
+static int virtio_i2c_setup_vqs(struct virtio_i2c *vi)
+{
+	struct virtio_device *vdev = vi->vdev;
+
+	vi->vq = virtio_find_single_vq(vdev, virtio_i2c_msg_done,
"i2c-msg");
+	return PTR_ERR_OR_ZERO(vi->vq);
+}
+
+static u32 virtio_i2c_func(struct i2c_adapter *adap)
+{
+	return I2C_FUNC_I2C | I2C_FUNC_SMBUS_EMUL;
+}
+
+static struct i2c_algorithm virtio_algorithm = {
+	.master_xfer = virtio_i2c_xfer,
+	.functionality = virtio_i2c_func,
+};
+
+static struct i2c_adapter virtio_adapter = {
+	.owner = THIS_MODULE,
+	.name = "Virtio I2C Adapter",
+	.class = I2C_CLASS_DEPRECATED,
+	.algo = &virtio_algorithm,
+};
+
+static int virtio_i2c_probe(struct virtio_device *vdev)
+{
+	struct device *pdev = vdev->dev.parent;
+	struct virtio_i2c *vi;
+	int ret;
+
+	vi = devm_kzalloc(&vdev->dev, sizeof(*vi), GFP_KERNEL);
+	if (!vi)
+		return -ENOMEM;
+
+	vdev->priv = vi;
+	vi->vdev = vdev;
+
+	mutex_init(&vi->i2c_lock);
+	init_completion(&vi->completion);
+
+	ret = virtio_i2c_setup_vqs(vi);
+	if (ret)
+		return ret;
+
+	vi->adap = virtio_adapter;
+	i2c_set_adapdata(&vi->adap, vi);
+	vi->adap.dev.parent = &vdev->dev;
+	/* Setup ACPI node for slave devices which will be probed through ACPI */
+	ACPI_COMPANION_SET(&vi->adap.dev, ACPI_COMPANION(pdev));
+	vi->adap.timeout = HZ / 10;
+	ret = i2c_add_adapter(&vi->adap);
+	if (ret) {
+		dev_err(&vdev->dev, "failed to add virtio-i2c adapter.\n");
+		virtio_i2c_del_vqs(vdev);
+	}
+
+	return ret;
+}
+
+static void virtio_i2c_remove(struct virtio_device *vdev)
+{
+	struct virtio_i2c *vi = vdev->priv;
+
+	i2c_del_adapter(&vi->adap);
+	virtio_i2c_del_vqs(vdev);
+}
+
+static struct virtio_device_id id_table[] = {
+	{ VIRTIO_ID_I2C_ADPTER, VIRTIO_DEV_ANY_ID },
+	{}
+};
+MODULE_DEVICE_TABLE(virtio, id_table);
+
+static int __maybe_unused virtio_i2c_freeze(struct virtio_device *vdev)
+{
+	virtio_i2c_del_vqs(vdev);
+	return 0;
+}
+
+static int __maybe_unused virtio_i2c_restore(struct virtio_device *vdev)
+{
+	return virtio_i2c_setup_vqs(vdev->priv);
+}
+
+static struct virtio_driver virtio_i2c_driver = {
+	.id_table	= id_table,
+	.probe		= virtio_i2c_probe,
+	.remove		= virtio_i2c_remove,
+	.driver	= {
+		.name	= "i2c_virtio",
+	},
+#ifdef CONFIG_PM_SLEEP
+	.freeze = virtio_i2c_freeze,
+	.restore = virtio_i2c_restore,
+#endif
+};
+module_virtio_driver(virtio_i2c_driver);
+
+MODULE_DESCRIPTION("Virtio i2c bus driver");
+MODULE_LICENSE("GPL");
diff --git a/include/uapi/linux/virtio_ids.h b/include/uapi/linux/virtio_ids.h
index b052355..398ef2d 100644
--- a/include/uapi/linux/virtio_ids.h
+++ b/include/uapi/linux/virtio_ids.h
@@ -48,5 +48,6 @@
 #define VIRTIO_ID_FS           26 /* virtio filesystem */
 #define VIRTIO_ID_PMEM         27 /* virtio pmem */
 #define VIRTIO_ID_MAC80211_HWSIM 29 /* virtio mac80211-hwsim */
+#define VIRTIO_ID_I2C_ADPTER   34 /* virtio i2c adpter */
 
 #endif /* _LINUX_VIRTIO_IDS_H */
-- 
2.7.4

Jason Wang

2020-Sep-03 06:12 UTC

head link

[PATCH] i2c: virtio: add a virtio i2c frontend driver

On 2020/9/3 ??1:34, Jie Deng wrote:> Add an I2C bus driver for virtio para-virtualization.
>
> The controller can be emulated by the backend driver in
> any device model software by following the virtio protocol.
>
> This driver communicates with the backend driver through a
> virtio I2C message structure which includes following parts:
>
> - Header: i2c_msg addr, flags, len.
> - Data buffer: the pointer to the i2c msg data.
> - Status: the processing result from the backend.
>
> People may implement different backend drivers to emulate
> different controllers according to their needs. A backend
> example can be found in the device model of the open source
> project ACRN. For more information, please refer to
> https://projectacrn.org.

May I know the reason why don't you use i2c or virtio directly?

>
> The virtio device ID 34 is used for this I2C adpter since IDs
> before 34 have been reserved by other virtio devices.

Is there a link to the spec patch?

Thanks

>
> Co-developed-by: Conghui Chen <conghui.chen at intel.com>
> Signed-off-by: Conghui Chen <conghui.chen at intel.com>
> Signed-off-by: Jie Deng <jie.deng at intel.com>
> Reviewed-by: Shuo Liu <shuo.a.liu at intel.com>
> Reviewed-by: Andy Shevchenko <andriy.shevchenko at linux.intel.com>
> ---
>   drivers/i2c/busses/Kconfig      |  11 ++
>   drivers/i2c/busses/Makefile     |   3 +
>   drivers/i2c/busses/i2c-virtio.c | 276
++++++++++++++++++++++++++++++++++++++++
>   include/uapi/linux/virtio_ids.h |   1 +
>   4 files changed, 291 insertions(+)
>   create mode 100644 drivers/i2c/busses/i2c-virtio.c
>
> diff --git a/drivers/i2c/busses/Kconfig b/drivers/i2c/busses/Kconfig
> index 293e7a0..70c8e30 100644
> --- a/drivers/i2c/busses/Kconfig
> +++ b/drivers/i2c/busses/Kconfig
> @@ -21,6 +21,17 @@ config I2C_ALI1535
>   	  This driver can also be built as a module.  If so, the module
>   	  will be called i2c-ali1535.
>   
> +config I2C_VIRTIO
> +	tristate "Virtio I2C Adapter"
> +	depends on VIRTIO
> +	help
> +	  If you say yes to this option, support will be included for the virtio
> +	  i2c adapter driver. The hardware can be emulated by any device model
> +	  software according to the virtio protocol.
> +
> +	  This driver can also be built as a module. If so, the module
> +	  will be called i2c-virtio.
> +
>   config I2C_ALI1563
>   	tristate "ALI 1563"
>   	depends on PCI
> diff --git a/drivers/i2c/busses/Makefile b/drivers/i2c/busses/Makefile
> index 19aff0e..821acfa 100644
> --- a/drivers/i2c/busses/Makefile
> +++ b/drivers/i2c/busses/Makefile
> @@ -6,6 +6,9 @@
>   # ACPI drivers
>   obj-$(CONFIG_I2C_SCMI)		+= i2c-scmi.o
>   
> +# VIRTIO I2C host controller driver
> +obj-$(CONFIG_I2C_VIRTIO)	+= i2c-virtio.o
> +
>   # PC SMBus host controller drivers
>   obj-$(CONFIG_I2C_ALI1535)	+= i2c-ali1535.o
>   obj-$(CONFIG_I2C_ALI1563)	+= i2c-ali1563.o
> diff --git a/drivers/i2c/busses/i2c-virtio.c
b/drivers/i2c/busses/i2c-virtio.c
> new file mode 100644
> index 0000000..47f9fd1
> --- /dev/null
> +++ b/drivers/i2c/busses/i2c-virtio.c
> @@ -0,0 +1,276 @@
> +// SPDX-License-Identifier: GPL-2.0-or-later
> +/*
> + * Virtio I2C Bus Driver
> + *
> + * Copyright (c) 2020 Intel Corporation. All rights reserved.
> + */
> +
> +#include <linux/acpi.h>
> +#include <linux/completion.h>
> +#include <linux/err.h>
> +#include <linux/i2c.h>
> +#include <linux/io.h>
> +#include <linux/jiffies.h>
> +#include <linux/kernel.h>
> +#include <linux/module.h>
> +#include <linux/platform_device.h>
> +#include <linux/wait.h>
> +
> +#include <linux/virtio.h>
> +#include <linux/virtio_ids.h>
> +#include <linux/virtio_config.h>
> +
> +#define VIRTIO_I2C_MSG_OK	0
> +#define VIRTIO_I2C_MSG_ERR	1
> +
> +/**
> + * struct virtio_i2c_hdr - the virtio I2C message header structure
> + * @addr: i2c_msg addr, the slave address
> + * @flags: i2c_msg flags
> + * @len: i2c_msg len
> + */
> +struct virtio_i2c_hdr {
> +	__virtio16 addr;
> +	__virtio16 flags;
> +	__virtio16 len;
> +} __packed;
> +
> +/**
> + * struct virtio_i2c_msg - the virtio I2C message structure
> + * @hdr: the virtio I2C message header
> + * @buf: virtio I2C message data buffer
> + * @status: the processing result from the backend
> + */
> +struct virtio_i2c_msg {
> +	struct virtio_i2c_hdr hdr;
> +	char *buf;
> +	u8 status;
> +};
> +
> +/**
> + * struct virtio_i2c - virtio I2C data
> + * @vdev: virtio device for this controller
> + * @completion: completion of virtio I2C message
> + * @adap: I2C adapter for this controller
> + * @i2c_lock: lock for virtqueue processing
> + * @vq: the virtio virtqueue for communication
> + */
> +struct virtio_i2c {
> +	struct virtio_device *vdev;
> +	struct completion completion;
> +	struct i2c_adapter adap;
> +	struct mutex i2c_lock;
> +	struct virtqueue *vq;
> +};
> +
> +static void virtio_i2c_msg_done(struct virtqueue *vq)
> +{
> +	struct virtio_i2c *vi = vq->vdev->priv;
> +
> +	complete(&vi->completion);
> +}
> +
> +static int virtio_i2c_add_msg(struct virtqueue *vq,
> +			      struct virtio_i2c_msg *vmsg,
> +			      struct i2c_msg *msg)
> +{
> +	struct scatterlist *sgs[3], hdr, bout, bin, status;
> +	int outcnt = 0, incnt = 0;
> +
> +	if (!msg->len)
> +		return -EINVAL;
> +
> +	vmsg->hdr.addr = msg->addr;
> +	vmsg->hdr.flags = msg->flags;
> +	vmsg->hdr.len = msg->len;
> +
> +	vmsg->buf = kzalloc(vmsg->hdr.len, GFP_KERNEL);
> +	if (!vmsg->buf)
> +		return -ENOMEM;
> +
> +	sg_init_one(&hdr, &vmsg->hdr, sizeof(struct virtio_i2c_hdr));
> +	sgs[outcnt++] = &hdr;
> +	if (vmsg->hdr.flags & I2C_M_RD) {
> +		sg_init_one(&bin, vmsg->buf, msg->len);
> +		sgs[outcnt + incnt++] = &bin;
> +	} else {
> +		memcpy(vmsg->buf, msg->buf, msg->len);
> +		sg_init_one(&bout, vmsg->buf, msg->len);
> +		sgs[outcnt++] = &bout;
> +	}
> +	sg_init_one(&status, &vmsg->status, sizeof(vmsg->status));
> +	sgs[outcnt + incnt++] = &status;
> +
> +	return virtqueue_add_sgs(vq, sgs, outcnt, incnt, vmsg, GFP_KERNEL);
> +}
> +
> +static int virtio_i2c_xfer(struct i2c_adapter *adap, struct i2c_msg *msgs,
int num)
> +{
> +	struct virtio_i2c *vi = i2c_get_adapdata(adap);
> +	struct virtio_i2c_msg *vmsg_o, *vmsg_i;
> +	struct virtqueue *vq = vi->vq;
> +	unsigned long time_left;
> +	int len, i, ret = 0;
> +
> +	vmsg_o = kzalloc(sizeof(*vmsg_o), GFP_KERNEL);
> +	if (!vmsg_o)
> +		return -ENOMEM;
> +
> +	mutex_lock(&vi->i2c_lock);
> +	vmsg_o->buf = NULL;
> +	for (i = 0; i < num; i++) {
> +		ret = virtio_i2c_add_msg(vq, vmsg_o, &msgs[i]);
> +		if (ret) {
> +			dev_err(&adap->dev, "failed to add msg[%d] to
virtqueue.\n", i);
> +			goto err_unlock_free;
> +		}
> +
> +		virtqueue_kick(vq);
> +
> +		time_left = wait_for_completion_timeout(&vi->completion,
adap->timeout);
> +		if (!time_left) {
> +			dev_err(&adap->dev, "msg[%d]: addr=0x%x timeout.\n",
i, msgs[i].addr);
> +			ret = i;
> +			goto err_unlock_free;
> +		}
> +
> +		vmsg_i = (struct virtio_i2c_msg *)virtqueue_get_buf(vq, &len);
> +		if (vmsg_i) {
> +			/* vmsg_i should point to the same address with vmsg_o */
> +			if (vmsg_i != vmsg_o) {
> +				dev_err(&adap->dev, "msg[%d]: addr=0x%x virtqueue
error.\n",
> +					i, vmsg_i->hdr.addr);
> +				ret = i;
> +				goto err_unlock_free;
> +			}
> +			if (vmsg_i->status != VIRTIO_I2C_MSG_OK) {
> +				dev_err(&adap->dev, "msg[%d]: addr=0x%x error=%d.\n",
> +					i, vmsg_i->hdr.addr, vmsg_i->status);
> +				ret = i;
> +				goto err_unlock_free;
> +			}
> +			if ((vmsg_i->hdr.flags & I2C_M_RD) &&
vmsg_i->hdr.len)
> +				memcpy(msgs[i].buf, vmsg_i->buf, vmsg_i->hdr.len);
> +
> +			kfree(vmsg_i->buf);
> +			vmsg_i->buf = NULL;
> +		}
> +		reinit_completion(&vi->completion);
> +	}
> +	if (i == num)
> +		ret = num;
> +
> +err_unlock_free:
> +	mutex_unlock(&vi->i2c_lock);
> +	kfree(vmsg_o->buf);
> +	kfree(vmsg_o);
> +	return ret;
> +}
> +
> +static void virtio_i2c_del_vqs(struct virtio_device *vdev)
> +{
> +	vdev->config->reset(vdev);
> +	vdev->config->del_vqs(vdev);
> +}
> +
> +static int virtio_i2c_setup_vqs(struct virtio_i2c *vi)
> +{
> +	struct virtio_device *vdev = vi->vdev;
> +
> +	vi->vq = virtio_find_single_vq(vdev, virtio_i2c_msg_done,
"i2c-msg");
> +	return PTR_ERR_OR_ZERO(vi->vq);
> +}
> +
> +static u32 virtio_i2c_func(struct i2c_adapter *adap)
> +{
> +	return I2C_FUNC_I2C | I2C_FUNC_SMBUS_EMUL;
> +}
> +
> +static struct i2c_algorithm virtio_algorithm = {
> +	.master_xfer = virtio_i2c_xfer,
> +	.functionality = virtio_i2c_func,
> +};
> +
> +static struct i2c_adapter virtio_adapter = {
> +	.owner = THIS_MODULE,
> +	.name = "Virtio I2C Adapter",
> +	.class = I2C_CLASS_DEPRECATED,
> +	.algo = &virtio_algorithm,
> +};
> +
> +static int virtio_i2c_probe(struct virtio_device *vdev)
> +{
> +	struct device *pdev = vdev->dev.parent;
> +	struct virtio_i2c *vi;
> +	int ret;
> +
> +	vi = devm_kzalloc(&vdev->dev, sizeof(*vi), GFP_KERNEL);
> +	if (!vi)
> +		return -ENOMEM;
> +
> +	vdev->priv = vi;
> +	vi->vdev = vdev;
> +
> +	mutex_init(&vi->i2c_lock);
> +	init_completion(&vi->completion);
> +
> +	ret = virtio_i2c_setup_vqs(vi);
> +	if (ret)
> +		return ret;
> +
> +	vi->adap = virtio_adapter;
> +	i2c_set_adapdata(&vi->adap, vi);
> +	vi->adap.dev.parent = &vdev->dev;
> +	/* Setup ACPI node for slave devices which will be probed through ACPI */
> +	ACPI_COMPANION_SET(&vi->adap.dev, ACPI_COMPANION(pdev));
> +	vi->adap.timeout = HZ / 10;
> +	ret = i2c_add_adapter(&vi->adap);
> +	if (ret) {
> +		dev_err(&vdev->dev, "failed to add virtio-i2c
adapter.\n");
> +		virtio_i2c_del_vqs(vdev);
> +	}
> +
> +	return ret;
> +}
> +
> +static void virtio_i2c_remove(struct virtio_device *vdev)
> +{
> +	struct virtio_i2c *vi = vdev->priv;
> +
> +	i2c_del_adapter(&vi->adap);
> +	virtio_i2c_del_vqs(vdev);
> +}
> +
> +static struct virtio_device_id id_table[] = {
> +	{ VIRTIO_ID_I2C_ADPTER, VIRTIO_DEV_ANY_ID },
> +	{}
> +};
> +MODULE_DEVICE_TABLE(virtio, id_table);
> +
> +static int __maybe_unused virtio_i2c_freeze(struct virtio_device *vdev)
> +{
> +	virtio_i2c_del_vqs(vdev);
> +	return 0;
> +}
> +
> +static int __maybe_unused virtio_i2c_restore(struct virtio_device *vdev)
> +{
> +	return virtio_i2c_setup_vqs(vdev->priv);
> +}
> +
> +static struct virtio_driver virtio_i2c_driver = {
> +	.id_table	= id_table,
> +	.probe		= virtio_i2c_probe,
> +	.remove		= virtio_i2c_remove,
> +	.driver	= {
> +		.name	= "i2c_virtio",
> +	},
> +#ifdef CONFIG_PM_SLEEP
> +	.freeze = virtio_i2c_freeze,
> +	.restore = virtio_i2c_restore,
> +#endif
> +};
> +module_virtio_driver(virtio_i2c_driver);
> +
> +MODULE_DESCRIPTION("Virtio i2c bus driver");
> +MODULE_LICENSE("GPL");
> diff --git a/include/uapi/linux/virtio_ids.h
b/include/uapi/linux/virtio_ids.h
> index b052355..398ef2d 100644
> --- a/include/uapi/linux/virtio_ids.h
> +++ b/include/uapi/linux/virtio_ids.h
> @@ -48,5 +48,6 @@
>   #define VIRTIO_ID_FS           26 /* virtio filesystem */
>   #define VIRTIO_ID_PMEM         27 /* virtio pmem */
>   #define VIRTIO_ID_MAC80211_HWSIM 29 /* virtio mac80211-hwsim */
> +#define VIRTIO_ID_I2C_ADPTER   34 /* virtio i2c adpter */
>   
>   #endif /* _LINUX_VIRTIO_IDS_H */

Jie Deng

2020-Sep-03 07:19 UTC

head link

[PATCH] i2c: virtio: add a virtio i2c frontend driver

On 2020/9/3 14:12, Jason Wang wrote:>
> On 2020/9/3 ??1:34, Jie Deng wrote:
>> Add an I2C bus driver for virtio para-virtualization.
>>
>> The controller can be emulated by the backend driver in
>> any device model software by following the virtio protocol.
>>
>> This driver communicates with the backend driver through a
>> virtio I2C message structure which includes following parts:
>>
>> - Header: i2c_msg addr, flags, len.
>> - Data buffer: the pointer to the i2c msg data.
>> - Status: the processing result from the backend.
>>
>> People may implement different backend drivers to emulate
>> different controllers according to their needs. A backend
>> example can be found in the device model of the open source
>> project ACRN. For more information, please refer to
>> https://projectacrn.org.
>
>
> May I know the reason why don't you use i2c or virtio directly?
>We don't want to add virtio drivers for every I2C devices in the guests.
This bus driver is designed to provide a way to flexibly expose the 
physical
I2C slave devices to the guest without adding or changing the drivers of 
the
I2C slave devices in the guest OS.

>
>>
>> The virtio device ID 34 is used for this I2C adpter since IDs
>> before 34 have been reserved by other virtio devices.
>
>
> Is there a link to the spec patch?
>
> Thanks
>I haven't submitted the patch to reserve the ID in spec yet.
I write the ID here because I want to see your opinions first.

Thanks

Michael S. Tsirkin

2020-Sep-03 09:58 UTC

head link

[PATCH] i2c: virtio: add a virtio i2c frontend driver

On Thu, Sep 03, 2020 at 01:34:45PM +0800, Jie Deng
wrote:> Add an I2C bus driver for virtio para-virtualization.
> 
> The controller can be emulated by the backend driver in
> any device model software by following the virtio protocol.
> 
> This driver communicates with the backend driver through a
> virtio I2C message structure which includes following parts:
> 
> - Header: i2c_msg addr, flags, len.
> - Data buffer: the pointer to the i2c msg data.
> - Status: the processing result from the backend.
> 
> People may implement different backend drivers to emulate
> different controllers according to their needs. A backend
> example can be found in the device model of the open source
> project ACRN. For more information, please refer to
> https://projectacrn.org.
> 
> The virtio device ID 34 is used for this I2C adpter since IDs
> before 34 have been reserved by other virtio devices.
Please reserve the ID with the virtio tc so no one conflicts.

> Co-developed-by: Conghui Chen <conghui.chen at intel.com>
> Signed-off-by: Conghui Chen <conghui.chen at intel.com>
> Signed-off-by: Jie Deng <jie.deng at intel.com>
> Reviewed-by: Shuo Liu <shuo.a.liu at intel.com>
> Reviewed-by: Andy Shevchenko <andriy.shevchenko at linux.intel.com>
> ---
>  drivers/i2c/busses/Kconfig      |  11 ++
>  drivers/i2c/busses/Makefile     |   3 +
>  drivers/i2c/busses/i2c-virtio.c | 276
++++++++++++++++++++++++++++++++++++++++
>  include/uapi/linux/virtio_ids.h |   1 +
>  4 files changed, 291 insertions(+)
>  create mode 100644 drivers/i2c/busses/i2c-virtio.c
> 
> diff --git a/drivers/i2c/busses/Kconfig b/drivers/i2c/busses/Kconfig
> index 293e7a0..70c8e30 100644
> --- a/drivers/i2c/busses/Kconfig
> +++ b/drivers/i2c/busses/Kconfig
> @@ -21,6 +21,17 @@ config I2C_ALI1535
>  	  This driver can also be built as a module.  If so, the module
>  	  will be called i2c-ali1535.
>  
> +config I2C_VIRTIO
> +	tristate "Virtio I2C Adapter"
> +	depends on VIRTIO
> +	help
> +	  If you say yes to this option, support will be included for the virtio
> +	  i2c adapter driver. The hardware can be emulated by any device model
> +	  software according to the virtio protocol.
> +
> +	  This driver can also be built as a module. If so, the module
> +	  will be called i2c-virtio.
> +
>  config I2C_ALI1563
>  	tristate "ALI 1563"
>  	depends on PCI
> diff --git a/drivers/i2c/busses/Makefile b/drivers/i2c/busses/Makefile
> index 19aff0e..821acfa 100644
> --- a/drivers/i2c/busses/Makefile
> +++ b/drivers/i2c/busses/Makefile
> @@ -6,6 +6,9 @@
>  # ACPI drivers
>  obj-$(CONFIG_I2C_SCMI)		+= i2c-scmi.o
>  
> +# VIRTIO I2C host controller driver
> +obj-$(CONFIG_I2C_VIRTIO)	+= i2c-virtio.o
> +
>  # PC SMBus host controller drivers
>  obj-$(CONFIG_I2C_ALI1535)	+= i2c-ali1535.o
>  obj-$(CONFIG_I2C_ALI1563)	+= i2c-ali1563.o
> diff --git a/drivers/i2c/busses/i2c-virtio.c
b/drivers/i2c/busses/i2c-virtio.c
> new file mode 100644
> index 0000000..47f9fd1
> --- /dev/null
> +++ b/drivers/i2c/busses/i2c-virtio.c
> @@ -0,0 +1,276 @@
> +// SPDX-License-Identifier: GPL-2.0-or-later
> +/*
> + * Virtio I2C Bus Driver
> + *
> + * Copyright (c) 2020 Intel Corporation. All rights reserved.
> + */
> +
> +#include <linux/acpi.h>
> +#include <linux/completion.h>
> +#include <linux/err.h>
> +#include <linux/i2c.h>
> +#include <linux/io.h>
> +#include <linux/jiffies.h>
> +#include <linux/kernel.h>
> +#include <linux/module.h>
> +#include <linux/platform_device.h>
> +#include <linux/wait.h>
> +
> +#include <linux/virtio.h>
> +#include <linux/virtio_ids.h>
> +#include <linux/virtio_config.h>
> +
> +#define VIRTIO_I2C_MSG_OK	0
> +#define VIRTIO_I2C_MSG_ERR	1
> +
> +/**
> + * struct virtio_i2c_hdr - the virtio I2C message header structure
> + * @addr: i2c_msg addr, the slave address
> + * @flags: i2c_msg flags
> + * @len: i2c_msg len
> + */
> +struct virtio_i2c_hdr {
> +	__virtio16 addr;
> +	__virtio16 flags;
> +	__virtio16 len;
> +} __packed;
virtio16 is for legacy devices, modern ones should be __le.
and  we don't really need to pack it I think.
> +
> +/**
> + * struct virtio_i2c_msg - the virtio I2C message structure
> + * @hdr: the virtio I2C message header
> + * @buf: virtio I2C message data buffer
> + * @status: the processing result from the backend
> + */
> +struct virtio_i2c_msg {
> +	struct virtio_i2c_hdr hdr;
> +	char *buf;
> +	u8 status;
> +};
> +
> +/**
> + * struct virtio_i2c - virtio I2C data
> + * @vdev: virtio device for this controller
> + * @completion: completion of virtio I2C message
> + * @adap: I2C adapter for this controller
> + * @i2c_lock: lock for virtqueue processing
> + * @vq: the virtio virtqueue for communication
> + */
> +struct virtio_i2c {
> +	struct virtio_device *vdev;
> +	struct completion completion;
> +	struct i2c_adapter adap;
> +	struct mutex i2c_lock;
> +	struct virtqueue *vq;
> +};
> +
> +static void virtio_i2c_msg_done(struct virtqueue *vq)
> +{
> +	struct virtio_i2c *vi = vq->vdev->priv;
> +
> +	complete(&vi->completion);
> +}
> +
> +static int virtio_i2c_add_msg(struct virtqueue *vq,
> +			      struct virtio_i2c_msg *vmsg,
> +			      struct i2c_msg *msg)
> +{
> +	struct scatterlist *sgs[3], hdr, bout, bin, status;
> +	int outcnt = 0, incnt = 0;
> +
> +	if (!msg->len)
> +		return -EINVAL;
> +
> +	vmsg->hdr.addr = msg->addr;
> +	vmsg->hdr.flags = msg->flags;
> +	vmsg->hdr.len = msg->len;
> +
> +	vmsg->buf = kzalloc(vmsg->hdr.len, GFP_KERNEL);
> +	if (!vmsg->buf)
> +		return -ENOMEM;
> +
> +	sg_init_one(&hdr, &vmsg->hdr, sizeof(struct virtio_i2c_hdr));
> +	sgs[outcnt++] = &hdr;
> +	if (vmsg->hdr.flags & I2C_M_RD) {
> +		sg_init_one(&bin, vmsg->buf, msg->len);
> +		sgs[outcnt + incnt++] = &bin;
> +	} else {
> +		memcpy(vmsg->buf, msg->buf, msg->len);
> +		sg_init_one(&bout, vmsg->buf, msg->len);
> +		sgs[outcnt++] = &bout;
> +	}
> +	sg_init_one(&status, &vmsg->status, sizeof(vmsg->status));
> +	sgs[outcnt + incnt++] = &status;
> +
> +	return virtqueue_add_sgs(vq, sgs, outcnt, incnt, vmsg, GFP_KERNEL);
> +}
> +
> +static int virtio_i2c_xfer(struct i2c_adapter *adap, struct i2c_msg *msgs,
int num)
> +{
> +	struct virtio_i2c *vi = i2c_get_adapdata(adap);
> +	struct virtio_i2c_msg *vmsg_o, *vmsg_i;
> +	struct virtqueue *vq = vi->vq;
> +	unsigned long time_left;
> +	int len, i, ret = 0;
> +
> +	vmsg_o = kzalloc(sizeof(*vmsg_o), GFP_KERNEL);
> +	if (!vmsg_o)
> +		return -ENOMEM;
> +
> +	mutex_lock(&vi->i2c_lock);
> +	vmsg_o->buf = NULL;
> +	for (i = 0; i < num; i++) {
> +		ret = virtio_i2c_add_msg(vq, vmsg_o, &msgs[i]);
> +		if (ret) {
> +			dev_err(&adap->dev, "failed to add msg[%d] to
virtqueue.\n", i);
> +			goto err_unlock_free;
> +		}
> +
> +		virtqueue_kick(vq);
> +
> +		time_left = wait_for_completion_timeout(&vi->completion,
adap->timeout);
> +		if (!time_left) {
> +			dev_err(&adap->dev, "msg[%d]: addr=0x%x timeout.\n",
i, msgs[i].addr);
> +			ret = i;
> +			goto err_unlock_free;
> +		}
> +
> +		vmsg_i = (struct virtio_i2c_msg *)virtqueue_get_buf(vq, &len);
> +		if (vmsg_i) {
> +			/* vmsg_i should point to the same address with vmsg_o */
> +			if (vmsg_i != vmsg_o) {
> +				dev_err(&adap->dev, "msg[%d]: addr=0x%x virtqueue
error.\n",
> +					i, vmsg_i->hdr.addr);
> +				ret = i;
> +				goto err_unlock_free;
> +			}
> +			if (vmsg_i->status != VIRTIO_I2C_MSG_OK) {
> +				dev_err(&adap->dev, "msg[%d]: addr=0x%x error=%d.\n",
> +					i, vmsg_i->hdr.addr, vmsg_i->status);
> +				ret = i;
> +				goto err_unlock_free;
> +			}
> +			if ((vmsg_i->hdr.flags & I2C_M_RD) &&
vmsg_i->hdr.len)
> +				memcpy(msgs[i].buf, vmsg_i->buf, vmsg_i->hdr.len);
> +
> +			kfree(vmsg_i->buf);
> +			vmsg_i->buf = NULL;
> +		}
> +		reinit_completion(&vi->completion);
> +	}
> +	if (i == num)
> +		ret = num;
> +
> +err_unlock_free:
> +	mutex_unlock(&vi->i2c_lock);
> +	kfree(vmsg_o->buf);
> +	kfree(vmsg_o);
> +	return ret;
> +}
> +
> +static void virtio_i2c_del_vqs(struct virtio_device *vdev)
> +{
> +	vdev->config->reset(vdev);
> +	vdev->config->del_vqs(vdev);
> +}
> +
> +static int virtio_i2c_setup_vqs(struct virtio_i2c *vi)
> +{
> +	struct virtio_device *vdev = vi->vdev;
> +
> +	vi->vq = virtio_find_single_vq(vdev, virtio_i2c_msg_done,
"i2c-msg");
> +	return PTR_ERR_OR_ZERO(vi->vq);
> +}
> +
> +static u32 virtio_i2c_func(struct i2c_adapter *adap)
> +{
> +	return I2C_FUNC_I2C | I2C_FUNC_SMBUS_EMUL;
> +}
> +
> +static struct i2c_algorithm virtio_algorithm = {
> +	.master_xfer = virtio_i2c_xfer,
> +	.functionality = virtio_i2c_func,
> +};
> +
> +static struct i2c_adapter virtio_adapter = {
> +	.owner = THIS_MODULE,
> +	.name = "Virtio I2C Adapter",
> +	.class = I2C_CLASS_DEPRECATED,
> +	.algo = &virtio_algorithm,
> +};
> +
> +static int virtio_i2c_probe(struct virtio_device *vdev)
> +{
> +	struct device *pdev = vdev->dev.parent;
> +	struct virtio_i2c *vi;
> +	int ret;
> +
> +	vi = devm_kzalloc(&vdev->dev, sizeof(*vi), GFP_KERNEL);
> +	if (!vi)
> +		return -ENOMEM;
> +
> +	vdev->priv = vi;
> +	vi->vdev = vdev;
> +
> +	mutex_init(&vi->i2c_lock);
> +	init_completion(&vi->completion);
> +
> +	ret = virtio_i2c_setup_vqs(vi);
> +	if (ret)
> +		return ret;
> +
> +	vi->adap = virtio_adapter;
> +	i2c_set_adapdata(&vi->adap, vi);
> +	vi->adap.dev.parent = &vdev->dev;
> +	/* Setup ACPI node for slave devices which will be probed through ACPI */
> +	ACPI_COMPANION_SET(&vi->adap.dev, ACPI_COMPANION(pdev));
> +	vi->adap.timeout = HZ / 10;
> +	ret = i2c_add_adapter(&vi->adap);
> +	if (ret) {
> +		dev_err(&vdev->dev, "failed to add virtio-i2c
adapter.\n");
> +		virtio_i2c_del_vqs(vdev);
> +	}
> +
> +	return ret;
> +}
> +
> +static void virtio_i2c_remove(struct virtio_device *vdev)
> +{
> +	struct virtio_i2c *vi = vdev->priv;
> +
> +	i2c_del_adapter(&vi->adap);
> +	virtio_i2c_del_vqs(vdev);
> +}
> +
> +static struct virtio_device_id id_table[] = {
> +	{ VIRTIO_ID_I2C_ADPTER, VIRTIO_DEV_ANY_ID },
> +	{}
> +};
> +MODULE_DEVICE_TABLE(virtio, id_table);
> +
> +static int __maybe_unused virtio_i2c_freeze(struct virtio_device *vdev)
> +{
> +	virtio_i2c_del_vqs(vdev);
> +	return 0;
> +}
> +
> +static int __maybe_unused virtio_i2c_restore(struct virtio_device *vdev)
> +{
> +	return virtio_i2c_setup_vqs(vdev->priv);
> +}
> +
> +static struct virtio_driver virtio_i2c_driver = {
> +	.id_table	= id_table,
> +	.probe		= virtio_i2c_probe,
> +	.remove		= virtio_i2c_remove,
> +	.driver	= {
> +		.name	= "i2c_virtio",
> +	},
> +#ifdef CONFIG_PM_SLEEP
> +	.freeze = virtio_i2c_freeze,
> +	.restore = virtio_i2c_restore,
> +#endif
> +};
> +module_virtio_driver(virtio_i2c_driver);
> +
> +MODULE_DESCRIPTION("Virtio i2c bus driver");
> +MODULE_LICENSE("GPL");
> diff --git a/include/uapi/linux/virtio_ids.h
b/include/uapi/linux/virtio_ids.h
> index b052355..398ef2d 100644
> --- a/include/uapi/linux/virtio_ids.h
> +++ b/include/uapi/linux/virtio_ids.h
> @@ -48,5 +48,6 @@
>  #define VIRTIO_ID_FS           26 /* virtio filesystem */
>  #define VIRTIO_ID_PMEM         27 /* virtio pmem */
>  #define VIRTIO_ID_MAC80211_HWSIM 29 /* virtio mac80211-hwsim */
> +#define VIRTIO_ID_I2C_ADPTER   34 /* virtio i2c adpter */
>  
>  #endif /* _LINUX_VIRTIO_IDS_H */
> -- 
> 2.7.4

Andy Shevchenko

2020-Sep-03 10:20 UTC

head link

[PATCH] i2c: virtio: add a virtio i2c frontend driver

On Thu, Sep 03, 2020 at 01:34:45PM +0800, Jie Deng
wrote:> Add an I2C bus driver for virtio para-virtualization.
> 
> The controller can be emulated by the backend driver in
> any device model software by following the virtio protocol.
> 
> This driver communicates with the backend driver through a
> virtio I2C message structure which includes following parts:
> 
> - Header: i2c_msg addr, flags, len.
> - Data buffer: the pointer to the i2c msg data.
> - Status: the processing result from the backend.
> 
> People may implement different backend drivers to emulate
> different controllers according to their needs. A backend
> example can be found in the device model of the open source
> project ACRN. For more information, please refer to
> https://projectacrn.org.
> 
> The virtio device ID 34 is used for this I2C adpter since IDs
> before 34 have been reserved by other virtio devices.
Seems it's slightly different version to what I have reviewed internally.
My comments below. (I admit that some of them maybe new)

...
> +/**
> + * struct virtio_i2c_hdr - the virtio I2C message header structure
> + * @addr: i2c_msg addr, the slave address
> + * @flags: i2c_msg flags
> + * @len: i2c_msg len
> + */
> +struct virtio_i2c_hdr {
> +	__virtio16 addr;
> +	__virtio16 flags;
> +	__virtio16 len;
> +} __packed;
As Misha noticed and somewhere I saw 0-day reports these should be carefully
taken care of.

...
> +static int virtio_i2c_xfer(struct i2c_adapter *adap, struct i2c_msg *msgs,
int num)
> +{
> +	struct virtio_i2c *vi = i2c_get_adapdata(adap);
> +	struct virtio_i2c_msg *vmsg_o, *vmsg_i;
> +	struct virtqueue *vq = vi->vq;
> +	unsigned long time_left;
> +	int len, i, ret = 0;
> +
> +	vmsg_o = kzalloc(sizeof(*vmsg_o), GFP_KERNEL);
> +	if (!vmsg_o)
> +		return -ENOMEM;
> +
> +	mutex_lock(&vi->i2c_lock);
> +	vmsg_o->buf = NULL;
> +	for (i = 0; i < num; i++) {
> +		ret = virtio_i2c_add_msg(vq, vmsg_o, &msgs[i]);
> +		if (ret) {
> +			dev_err(&adap->dev, "failed to add msg[%d] to
virtqueue.\n", i);
> +			goto err_unlock_free;
break;
> +		}
> +
> +		virtqueue_kick(vq);
> +
> +		time_left = wait_for_completion_timeout(&vi->completion,
adap->timeout);
> +		if (!time_left) {
> +			dev_err(&adap->dev, "msg[%d]: addr=0x%x timeout.\n",
i, msgs[i].addr);
> +			ret = i;
> +			goto err_unlock_free;
break;

And so on.
> +		}
> +
> +		vmsg_i = (struct virtio_i2c_msg *)virtqueue_get_buf(vq, &len);
> +		if (vmsg_i) {
> +			/* vmsg_i should point to the same address with vmsg_o */
> +			if (vmsg_i != vmsg_o) {
> +				dev_err(&adap->dev, "msg[%d]: addr=0x%x virtqueue
error.\n",
> +					i, vmsg_i->hdr.addr);
> +				ret = i;
> +				goto err_unlock_free;
> +			}
> +			if (vmsg_i->status != VIRTIO_I2C_MSG_OK) {
> +				dev_err(&adap->dev, "msg[%d]: addr=0x%x error=%d.\n",
> +					i, vmsg_i->hdr.addr, vmsg_i->status);
> +				ret = i;
> +				goto err_unlock_free;
> +			}
> +			if ((vmsg_i->hdr.flags & I2C_M_RD) &&
vmsg_i->hdr.len)
> +				memcpy(msgs[i].buf, vmsg_i->buf, vmsg_i->hdr.len);
> +
> +			kfree(vmsg_i->buf);
> +			vmsg_i->buf = NULL;
> +		}
> +		reinit_completion(&vi->completion);
> +	}
> +	if (i == num)
> +		ret = num;
And this conditional seems a dup of the for-loop successfully iterating over
entire queue.
> +err_unlock_free:
Redundant.
> +	mutex_unlock(&vi->i2c_lock);
> +	kfree(vmsg_o->buf);
> +	kfree(vmsg_o);
> +	return ret;
> +}
...
> +	vi->adap.timeout = HZ / 10;
+ Blank line.
> +	ret = i2c_add_adapter(&vi->adap);
> +	if (ret) {
> +		dev_err(&vdev->dev, "failed to add virtio-i2c
adapter.\n");
> +		virtio_i2c_del_vqs(vdev);
Usually we do clean up followed by message.
> +	}
> +
> +	return ret;

-- 
With Best Regards,
Andy Shevchenko

Jason Wang

2020-Sep-04 04:06 UTC

head link

[PATCH] i2c: virtio: add a virtio i2c frontend driver

On 2020/9/3 ??1:34, Jie Deng wrote:> Add an I2C bus driver for virtio para-virtualization.
>
> The controller can be emulated by the backend driver in
> any device model software by following the virtio protocol.
>
> This driver communicates with the backend driver through a
> virtio I2C message structure which includes following parts:
>
> - Header: i2c_msg addr, flags, len.
> - Data buffer: the pointer to the i2c msg data.
> - Status: the processing result from the backend.
>
> People may implement different backend drivers to emulate
> different controllers according to their needs. A backend
> example can be found in the device model of the open source
> project ACRN. For more information, please refer to
> https://projectacrn.org.
>
> The virtio device ID 34 is used for this I2C adpter since IDs
> before 34 have been reserved by other virtio devices.
>
> Co-developed-by: Conghui Chen <conghui.chen at intel.com>
> Signed-off-by: Conghui Chen <conghui.chen at intel.com>
> Signed-off-by: Jie Deng <jie.deng at intel.com>
> Reviewed-by: Shuo Liu <shuo.a.liu at intel.com>
> Reviewed-by: Andy Shevchenko <andriy.shevchenko at linux.intel.com>
> ---
>   drivers/i2c/busses/Kconfig      |  11 ++
>   drivers/i2c/busses/Makefile     |   3 +
>   drivers/i2c/busses/i2c-virtio.c | 276
++++++++++++++++++++++++++++++++++++++++
>   include/uapi/linux/virtio_ids.h |   1 +
>   4 files changed, 291 insertions(+)
>   create mode 100644 drivers/i2c/busses/i2c-virtio.c
>
> diff --git a/drivers/i2c/busses/Kconfig b/drivers/i2c/busses/Kconfig
> index 293e7a0..70c8e30 100644
> --- a/drivers/i2c/busses/Kconfig
> +++ b/drivers/i2c/busses/Kconfig
> @@ -21,6 +21,17 @@ config I2C_ALI1535
>   	  This driver can also be built as a module.  If so, the module
>   	  will be called i2c-ali1535.
>   
> +config I2C_VIRTIO
> +	tristate "Virtio I2C Adapter"
> +	depends on VIRTIO

I guess it should depend on some I2C module here.

> +	help
> +	  If you say yes to this option, support will be included for the virtio
> +	  i2c adapter driver. The hardware can be emulated by any device model
> +	  software according to the virtio protocol.
> +
> +	  This driver can also be built as a module. If so, the module
> +	  will be called i2c-virtio.
> +
>   config I2C_ALI1563
>   	tristate "ALI 1563"
>   	depends on PCI
> diff --git a/drivers/i2c/busses/Makefile b/drivers/i2c/busses/Makefile
> index 19aff0e..821acfa 100644
> --- a/drivers/i2c/busses/Makefile
> +++ b/drivers/i2c/busses/Makefile
> @@ -6,6 +6,9 @@
>   # ACPI drivers
>   obj-$(CONFIG_I2C_SCMI)		+= i2c-scmi.o
>   
> +# VIRTIO I2C host controller driver
> +obj-$(CONFIG_I2C_VIRTIO)	+= i2c-virtio.o
> +
>   # PC SMBus host controller drivers
>   obj-$(CONFIG_I2C_ALI1535)	+= i2c-ali1535.o
>   obj-$(CONFIG_I2C_ALI1563)	+= i2c-ali1563.o
> diff --git a/drivers/i2c/busses/i2c-virtio.c
b/drivers/i2c/busses/i2c-virtio.c
> new file mode 100644
> index 0000000..47f9fd1
> --- /dev/null
> +++ b/drivers/i2c/busses/i2c-virtio.c
> @@ -0,0 +1,276 @@
> +// SPDX-License-Identifier: GPL-2.0-or-later
> +/*
> + * Virtio I2C Bus Driver
> + *
> + * Copyright (c) 2020 Intel Corporation. All rights reserved.
> + */
> +
> +#include <linux/acpi.h>
> +#include <linux/completion.h>
> +#include <linux/err.h>
> +#include <linux/i2c.h>
> +#include <linux/io.h>
> +#include <linux/jiffies.h>
> +#include <linux/kernel.h>
> +#include <linux/module.h>
> +#include <linux/platform_device.h>
> +#include <linux/wait.h>
> +
> +#include <linux/virtio.h>
> +#include <linux/virtio_ids.h>
> +#include <linux/virtio_config.h>
> +
> +#define VIRTIO_I2C_MSG_OK	0
> +#define VIRTIO_I2C_MSG_ERR	1
> +
> +/**
> + * struct virtio_i2c_hdr - the virtio I2C message header structure
> + * @addr: i2c_msg addr, the slave address
> + * @flags: i2c_msg flags
> + * @len: i2c_msg len
> + */
> +struct virtio_i2c_hdr {
> +	__virtio16 addr;
> +	__virtio16 flags;
> +	__virtio16 len;
> +} __packed;
> +
> +/**
> + * struct virtio_i2c_msg - the virtio I2C message structure
> + * @hdr: the virtio I2C message header
> + * @buf: virtio I2C message data buffer
> + * @status: the processing result from the backend
> + */
> +struct virtio_i2c_msg {
> +	struct virtio_i2c_hdr hdr;
> +	char *buf;
> +	u8 status;

Any reason for separating status out of virtio_i2c_hdr?

> +};
> +
> +/**
> + * struct virtio_i2c - virtio I2C data
> + * @vdev: virtio device for this controller
> + * @completion: completion of virtio I2C message
> + * @adap: I2C adapter for this controller
> + * @i2c_lock: lock for virtqueue processing
> + * @vq: the virtio virtqueue for communication
> + */
> +struct virtio_i2c {
> +	struct virtio_device *vdev;
> +	struct completion completion;
> +	struct i2c_adapter adap;
> +	struct mutex i2c_lock;
> +	struct virtqueue *vq;
> +};
> +
> +static void virtio_i2c_msg_done(struct virtqueue *vq)
> +{
> +	struct virtio_i2c *vi = vq->vdev->priv;
> +
> +	complete(&vi->completion);
> +}
> +
> +static int virtio_i2c_add_msg(struct virtqueue *vq,
> +			      struct virtio_i2c_msg *vmsg,
> +			      struct i2c_msg *msg)
> +{
> +	struct scatterlist *sgs[3], hdr, bout, bin, status;
> +	int outcnt = 0, incnt = 0;
> +
> +	if (!msg->len)
> +		return -EINVAL;
> +
> +	vmsg->hdr.addr = msg->addr;
> +	vmsg->hdr.flags = msg->flags;
> +	vmsg->hdr.len = msg->len;

Missing endian conversion?

> +
> +	vmsg->buf = kzalloc(vmsg->hdr.len, GFP_KERNEL);
> +	if (!vmsg->buf)
> +		return -ENOMEM;
> +
> +	sg_init_one(&hdr, &vmsg->hdr, sizeof(struct virtio_i2c_hdr));
> +	sgs[outcnt++] = &hdr;
> +	if (vmsg->hdr.flags & I2C_M_RD) {
> +		sg_init_one(&bin, vmsg->buf, msg->len);
> +		sgs[outcnt + incnt++] = &bin;
> +	} else {
> +		memcpy(vmsg->buf, msg->buf, msg->len);
> +		sg_init_one(&bout, vmsg->buf, msg->len);
> +		sgs[outcnt++] = &bout;
> +	}
> +	sg_init_one(&status, &vmsg->status, sizeof(vmsg->status));
> +	sgs[outcnt + incnt++] = &status;
> +
> +	return virtqueue_add_sgs(vq, sgs, outcnt, incnt, vmsg, GFP_KERNEL);
> +}
> +
> +static int virtio_i2c_xfer(struct i2c_adapter *adap, struct i2c_msg *msgs,
int num)
> +{
> +	struct virtio_i2c *vi = i2c_get_adapdata(adap);
> +	struct virtio_i2c_msg *vmsg_o, *vmsg_i;
> +	struct virtqueue *vq = vi->vq;
> +	unsigned long time_left;
> +	int len, i, ret = 0;
> +
> +	vmsg_o = kzalloc(sizeof(*vmsg_o), GFP_KERNEL);
> +	if (!vmsg_o)
> +		return -ENOMEM;

It looks to me we can avoid the allocation by embedding virtio_i2c_msg 
into struct virtio_i2c;

> +
> +	mutex_lock(&vi->i2c_lock);
> +	vmsg_o->buf = NULL;
> +	for (i = 0; i < num; i++) {
> +		ret = virtio_i2c_add_msg(vq, vmsg_o, &msgs[i]);
> +		if (ret) {
> +			dev_err(&adap->dev, "failed to add msg[%d] to
virtqueue.\n", i);
> +			goto err_unlock_free;
> +		}
> +
> +		virtqueue_kick(vq);
> +
> +		time_left = wait_for_completion_timeout(&vi->completion,
adap->timeout);
> +		if (!time_left) {
> +			dev_err(&adap->dev, "msg[%d]: addr=0x%x timeout.\n",
i, msgs[i].addr);
> +			ret = i;
> +			goto err_unlock_free;
> +		}
> +
> +		vmsg_i = (struct virtio_i2c_msg *)virtqueue_get_buf(vq, &len);
> +		if (vmsg_i) {
> +			/* vmsg_i should point to the same address with vmsg_o */
> +			if (vmsg_i != vmsg_o) {
> +				dev_err(&adap->dev, "msg[%d]: addr=0x%x virtqueue
error.\n",
> +					i, vmsg_i->hdr.addr);
> +				ret = i;
> +				goto err_unlock_free;
> +			}

Does this imply in order completion of i2c device?? (E.g what happens if 
multiple virtio i2c requests are submitted)

Btw, this always use a single descriptor once a time which makes me 
suspect if a virtqueue(virtio) is really needed. It looks to me we can 
utilize the virtqueue by submit the request in a batch.
> +			if (vmsg_i->status != VIRTIO_I2C_MSG_OK) {
> +				dev_err(&adap->dev, "msg[%d]: addr=0x%x error=%d.\n",
> +					i, vmsg_i->hdr.addr, vmsg_i->status);
> +				ret = i;
> +				goto err_unlock_free;
> +			}
> +			if ((vmsg_i->hdr.flags & I2C_M_RD) &&
vmsg_i->hdr.len)
> +				memcpy(msgs[i].buf, vmsg_i->buf, vmsg_i->hdr.len);
> +
> +			kfree(vmsg_i->buf);
> +			vmsg_i->buf = NULL;
> +		}
> +		reinit_completion(&vi->completion);
> +	}
> +	if (i == num)
> +		ret = num;
> +
> +err_unlock_free:
> +	mutex_unlock(&vi->i2c_lock);
> +	kfree(vmsg_o->buf);
> +	kfree(vmsg_o);
> +	return ret;
> +}
> +
> +static void virtio_i2c_del_vqs(struct virtio_device *vdev)
> +{
> +	vdev->config->reset(vdev);

Why need reset here?

Thanks

> +	vdev->config->del_vqs(vdev);
> +}
> +
> +static int virtio_i2c_setup_vqs(struct virtio_i2c *vi)
> +{
> +	struct virtio_device *vdev = vi->vdev;
> +
> +	vi->vq = virtio_find_single_vq(vdev, virtio_i2c_msg_done,
"i2c-msg");

We've in the scope of ic2, so "msg" should be sufficient.

> +	return PTR_ERR_OR_ZERO(vi->vq);
> +}
> +
> +static u32 virtio_i2c_func(struct i2c_adapter *adap)
> +{
> +	return I2C_FUNC_I2C | I2C_FUNC_SMBUS_EMUL;
> +}
> +
> +static struct i2c_algorithm virtio_algorithm = {
> +	.master_xfer = virtio_i2c_xfer,
> +	.functionality = virtio_i2c_func,
> +};
> +
> +static struct i2c_adapter virtio_adapter = {
> +	.owner = THIS_MODULE,
> +	.name = "Virtio I2C Adapter",
> +	.class = I2C_CLASS_DEPRECATED,
> +	.algo = &virtio_algorithm,
> +};
> +
> +static int virtio_i2c_probe(struct virtio_device *vdev)
> +{
> +	struct device *pdev = vdev->dev.parent;
> +	struct virtio_i2c *vi;
> +	int ret;
> +
> +	vi = devm_kzalloc(&vdev->dev, sizeof(*vi), GFP_KERNEL);
> +	if (!vi)
> +		return -ENOMEM;
> +
> +	vdev->priv = vi;
> +	vi->vdev = vdev;
> +
> +	mutex_init(&vi->i2c_lock);
> +	init_completion(&vi->completion);
> +
> +	ret = virtio_i2c_setup_vqs(vi);
> +	if (ret)
> +		return ret;
> +
> +	vi->adap = virtio_adapter;
> +	i2c_set_adapdata(&vi->adap, vi);
> +	vi->adap.dev.parent = &vdev->dev;
> +	/* Setup ACPI node for slave devices which will be probed through ACPI */
> +	ACPI_COMPANION_SET(&vi->adap.dev, ACPI_COMPANION(pdev));
> +	vi->adap.timeout = HZ / 10;
> +	ret = i2c_add_adapter(&vi->adap);
> +	if (ret) {
> +		dev_err(&vdev->dev, "failed to add virtio-i2c
adapter.\n");
> +		virtio_i2c_del_vqs(vdev);
> +	}
> +
> +	return ret;
> +}
> +
> +static void virtio_i2c_remove(struct virtio_device *vdev)
> +{
> +	struct virtio_i2c *vi = vdev->priv;
> +
> +	i2c_del_adapter(&vi->adap);
> +	virtio_i2c_del_vqs(vdev);
> +}
> +
> +static struct virtio_device_id id_table[] = {
> +	{ VIRTIO_ID_I2C_ADPTER, VIRTIO_DEV_ANY_ID },
> +	{}
> +};
> +MODULE_DEVICE_TABLE(virtio, id_table);
> +
> +static int __maybe_unused virtio_i2c_freeze(struct virtio_device *vdev)
> +{
> +	virtio_i2c_del_vqs(vdev);
> +	return 0;
> +}
> +
> +static int __maybe_unused virtio_i2c_restore(struct virtio_device *vdev)
> +{
> +	return virtio_i2c_setup_vqs(vdev->priv);
> +}
> +
> +static struct virtio_driver virtio_i2c_driver = {
> +	.id_table	= id_table,
> +	.probe		= virtio_i2c_probe,
> +	.remove		= virtio_i2c_remove,
> +	.driver	= {
> +		.name	= "i2c_virtio",
> +	},
> +#ifdef CONFIG_PM_SLEEP
> +	.freeze = virtio_i2c_freeze,
> +	.restore = virtio_i2c_restore,
> +#endif
> +};
> +module_virtio_driver(virtio_i2c_driver);
> +
> +MODULE_DESCRIPTION("Virtio i2c bus driver");
> +MODULE_LICENSE("GPL");
> diff --git a/include/uapi/linux/virtio_ids.h
b/include/uapi/linux/virtio_ids.h
> index b052355..398ef2d 100644
> --- a/include/uapi/linux/virtio_ids.h
> +++ b/include/uapi/linux/virtio_ids.h
> @@ -48,5 +48,6 @@
>   #define VIRTIO_ID_FS           26 /* virtio filesystem */
>   #define VIRTIO_ID_PMEM         27 /* virtio pmem */
>   #define VIRTIO_ID_MAC80211_HWSIM 29 /* virtio mac80211-hwsim */
> +#define VIRTIO_ID_I2C_ADPTER   34 /* virtio i2c adpter */
>   
>   #endif /* _LINUX_VIRTIO_IDS_H */

Jie Deng

2020-Sep-04 05:28 UTC

head link

[PATCH] i2c: virtio: add a virtio i2c frontend driver

On 2020/9/3 17:58, Michael S. Tsirkin wrote:> On Thu, Sep 03, 2020 at 01:34:45PM +0800, Jie Deng wrote:
>> Add an I2C bus driver for virtio para-virtualization.
>>
>> The controller can be emulated by the backend driver in
>> any device model software by following the virtio protocol.
>>
>> This driver communicates with the backend driver through a
>> virtio I2C message structure which includes following parts:
>>
>> - Header: i2c_msg addr, flags, len.
>> - Data buffer: the pointer to the i2c msg data.
>> - Status: the processing result from the backend.
>>
>> People may implement different backend drivers to emulate
>> different controllers according to their needs. A backend
>> example can be found in the device model of the open source
>> project ACRN. For more information, please refer to
>> https://projectacrn.org.
>>
>> The virtio device ID 34 is used for this I2C adpter since IDs
>> before 34 have been reserved by other virtio devices.
> Please reserve the ID with the virtio tc so no one conflicts.
>Sure. I will send a patch to request the ID.

>
> +
> +/**
> + * struct virtio_i2c_hdr - the virtio I2C message header structure
> + * @addr: i2c_msg addr, the slave address
> + * @flags: i2c_msg flags
> + * @len: i2c_msg len
> + */
> +struct virtio_i2c_hdr {
> +	__virtio16 addr;
> +	__virtio16 flags;
> +	__virtio16 len;
> +} __packed;
> virtio16 is for legacy devices, modern ones should be __le.
> and  we don't really need to pack it I think.
Right. I will fix these. Thanks.

Jie Deng

2020-Sep-04 06:08 UTC

head link

[PATCH] i2c: virtio: add a virtio i2c frontend driver

On 2020/9/3 18:20, Andy Shevchenko wrote:> On Thu, Sep 03, 2020 at 01:34:45PM +0800, Jie Deng wrote:
>> Add an I2C bus driver for virtio para-virtualization.
>>
>> The controller can be emulated by the backend driver in
>> any device model software by following the virtio protocol.
>>
>> This driver communicates with the backend driver through a
>> virtio I2C message structure which includes following parts:
>>
>> - Header: i2c_msg addr, flags, len.
>> - Data buffer: the pointer to the i2c msg data.
>> - Status: the processing result from the backend.
>>
>> People may implement different backend drivers to emulate
>> different controllers according to their needs. A backend
>> example can be found in the device model of the open source
>> project ACRN. For more information, please refer to
>> https://projectacrn.org.
>>
>> The virtio device ID 34 is used for this I2C adpter since IDs
>> before 34 have been reserved by other virtio devices.
> Seems it's slightly different version to what I have reviewed
internally.
> My comments below. (I admit that some of them maybe new)
>
> ...
Yeah... Some new devices have been added into the virtio spec during 
these days.

>> +/**
>> + * struct virtio_i2c_hdr - the virtio I2C message header structure
>> + * @addr: i2c_msg addr, the slave address
>> + * @flags: i2c_msg flags
>> + * @len: i2c_msg len
>> + */
>> +struct virtio_i2c_hdr {
>> +	__virtio16 addr;
>> +	__virtio16 flags;
>> +	__virtio16 len;
>> +} __packed;
> As Misha noticed and somewhere I saw 0-day reports these should be
carefully
> taken care of.
>
> ...
Sure. Will fix these.

>> +static int virtio_i2c_xfer(struct i2c_adapter *adap, struct i2c_msg
*msgs, int num)
>> +{
>> +	struct virtio_i2c *vi = i2c_get_adapdata(adap);
>> +	struct virtio_i2c_msg *vmsg_o, *vmsg_i;
>> +	struct virtqueue *vq = vi->vq;
>> +	unsigned long time_left;
>> +	int len, i, ret = 0;
>> +
>> +	vmsg_o = kzalloc(sizeof(*vmsg_o), GFP_KERNEL);
>> +	if (!vmsg_o)
>> +		return -ENOMEM;
>> +
>> +	mutex_lock(&vi->i2c_lock);
>> +	vmsg_o->buf = NULL;
>> +	for (i = 0; i < num; i++) {
>> +		ret = virtio_i2c_add_msg(vq, vmsg_o, &msgs[i]);
>> +		if (ret) {
>> +			dev_err(&adap->dev, "failed to add msg[%d] to
virtqueue.\n", i);
>> +			goto err_unlock_free;
> break;
OK.

>> +		}
>> +
>> +		virtqueue_kick(vq);
>> +
>> +		time_left = wait_for_completion_timeout(&vi->completion,
adap->timeout);
>> +		if (!time_left) {
>> +			dev_err(&adap->dev, "msg[%d]: addr=0x%x
timeout.\n", i, msgs[i].addr);
>> +			ret = i;
>> +			goto err_unlock_free;
> break;
>
> And so on.
OK.>> +		}
>> +
>> +		vmsg_i = (struct virtio_i2c_msg *)virtqueue_get_buf(vq, &len);
>> +		if (vmsg_i) {
>> +			/* vmsg_i should point to the same address with vmsg_o */
>> +			if (vmsg_i != vmsg_o) {
>> +				dev_err(&adap->dev, "msg[%d]: addr=0x%x virtqueue
error.\n",
>> +					i, vmsg_i->hdr.addr);
>> +				ret = i;
>> +				goto err_unlock_free;
>> +			}
>> +			if (vmsg_i->status != VIRTIO_I2C_MSG_OK) {
>> +				dev_err(&adap->dev, "msg[%d]: addr=0x%x
error=%d.\n",
>> +					i, vmsg_i->hdr.addr, vmsg_i->status);
>> +				ret = i;
>> +				goto err_unlock_free;
>> +			}
>> +			if ((vmsg_i->hdr.flags & I2C_M_RD) &&
vmsg_i->hdr.len)
>> +				memcpy(msgs[i].buf, vmsg_i->buf, vmsg_i->hdr.len);
>> +
>> +			kfree(vmsg_i->buf);
>> +			vmsg_i->buf = NULL;
>> +		}
>> +		reinit_completion(&vi->completion);
>> +	}
>> +	if (i == num)
>> +		ret = num;
> And this conditional seems a dup of the for-loop successfully iterating
over
> entire queue.You are right.
We may save several lines of code by using "Return (ret<0) ? ret :
i" at
the end.

>> +err_unlock_free:
> Redundant.
OK.>> +	mutex_unlock(&vi->i2c_lock);
>> +	kfree(vmsg_o->buf);
>> +	kfree(vmsg_o);
>> +	return ret;
>> +}
> ...
>
>> +	vi->adap.timeout = HZ / 10;
> + Blank line.
OK.>> +	ret = i2c_add_adapter(&vi->adap);
>> +	if (ret) {
>> +		dev_err(&vdev->dev, "failed to add virtio-i2c
adapter.\n");
>> +		virtio_i2c_del_vqs(vdev);
> Usually we do clean up followed by message.
I will change the order. Thank you.>> +	}
>> +
>> +	return ret;
>

Jie Deng

2020-Sep-04 13:21 UTC

head link

[PATCH] i2c: virtio: add a virtio i2c frontend driver

On 2020/9/4 12:06, Jason Wang wrote:>
>> diff --git a/drivers/i2c/busses/Kconfig b/drivers/i2c/busses/Kconfig
>> index 293e7a0..70c8e30 100644
>> --- a/drivers/i2c/busses/Kconfig
>> +++ b/drivers/i2c/busses/Kconfig
>> @@ -21,6 +21,17 @@ config I2C_ALI1535
>> ??????? This driver can also be built as a module.? If so, the module
>> ??????? will be called i2c-ali1535.
>> ? +config I2C_VIRTIO
>> +??? tristate "Virtio I2C Adapter"
>> +??? depends on VIRTIO
>
>
> I guess it should depend on some I2C module here.
>The dependency of I2C is included in the Kconfig in its parent directory.
So there is nothing special to add here.

>
>>
>> +struct virtio_i2c_msg {
>> +??? struct virtio_i2c_hdr hdr;
>> +??? char *buf;
>> +??? u8 status;
>
>
> Any reason for separating status out of virtio_i2c_hdr?
>The status is not from i2c_msg. So I put it out of virtio_i2c_hdr.
>
>> +};
>> +
>> +/**
>> + * struct virtio_i2c - virtio I2C data
>> + * @vdev: virtio device for this controller
>> + * @completion: completion of virtio I2C message
>> + * @adap: I2C adapter for this controller
>> + * @i2c_lock: lock for virtqueue processing
>> + * @vq: the virtio virtqueue for communication
>> + */
>> +struct virtio_i2c {
>> +??? struct virtio_device *vdev;
>> +??? struct completion completion;
>> +??? struct i2c_adapter adap;
>> +??? struct mutex i2c_lock;
>> +??? struct virtqueue *vq;
>> +};
>> +
>> +static void virtio_i2c_msg_done(struct virtqueue *vq)
>> +{
>> +??? struct virtio_i2c *vi = vq->vdev->priv;
>> +
>> +??? complete(&vi->completion);
>> +}
>> +
>> +static int virtio_i2c_add_msg(struct virtqueue *vq,
>> +????????????????? struct virtio_i2c_msg *vmsg,
>> +????????????????? struct i2c_msg *msg)
>> +{
>> +??? struct scatterlist *sgs[3], hdr, bout, bin, status;
>> +??? int outcnt = 0, incnt = 0;
>> +
>> +??? if (!msg->len)
>> +??????? return -EINVAL;
>> +
>> +??? vmsg->hdr.addr = msg->addr;
>> +??? vmsg->hdr.flags = msg->flags;
>> +??? vmsg->hdr.len = msg->len;
>
>
> Missing endian conversion?
>
You are right. Need conversion here.>
>> +
>> +??? vmsg->buf = kzalloc(vmsg->hdr.len, GFP_KERNEL);
>> +??? if (!vmsg->buf)
>> +??????? return -ENOMEM;
>> +
>> +??? sg_init_one(&hdr, &vmsg->hdr, sizeof(struct
virtio_i2c_hdr));
>> +??? sgs[outcnt++] = &hdr;
>> +??? if (vmsg->hdr.flags & I2C_M_RD) {
>> +??????? sg_init_one(&bin, vmsg->buf, msg->len);
>> +??????? sgs[outcnt + incnt++] = &bin;
>> +??? } else {
>> +??????? memcpy(vmsg->buf, msg->buf, msg->len);
>> +??????? sg_init_one(&bout, vmsg->buf, msg->len);
>> +??????? sgs[outcnt++] = &bout;
>> +??? }
>> +??? sg_init_one(&status, &vmsg->status,
sizeof(vmsg->status));
>> +??? sgs[outcnt + incnt++] = &status;
>> +
>> +??? return virtqueue_add_sgs(vq, sgs, outcnt, incnt, vmsg,
GFP_KERNEL);
>> +}
>> +
>> +static int virtio_i2c_xfer(struct i2c_adapter *adap, struct i2c_msg 
>> *msgs, int num)
>> +{
>> +??? struct virtio_i2c *vi = i2c_get_adapdata(adap);
>> +??? struct virtio_i2c_msg *vmsg_o, *vmsg_i;
>> +??? struct virtqueue *vq = vi->vq;
>> +??? unsigned long time_left;
>> +??? int len, i, ret = 0;
>> +
>> +??? vmsg_o = kzalloc(sizeof(*vmsg_o), GFP_KERNEL);
>> +??? if (!vmsg_o)
>> +??????? return -ENOMEM;
>
>
> It looks to me we can avoid the allocation by embedding virtio_i2c_msg 
> into struct virtio_i2c;
>Yeah... That's better. Thanks.

>
>> +
>> +??? mutex_lock(&vi->i2c_lock);
>> +??? vmsg_o->buf = NULL;
>> +??? for (i = 0; i < num; i++) {
>> +??????? ret = virtio_i2c_add_msg(vq, vmsg_o, &msgs[i]);
>> +??????? if (ret) {
>> +??????????? dev_err(&adap->dev, "failed to add msg[%d] to 
>> virtqueue.\n", i);
>> +??????????? goto err_unlock_free;
>> +??????? }
>> +
>> +??????? virtqueue_kick(vq);
>> +
>> +??????? time_left =
wait_for_completion_timeout(&vi->completion,
>> adap->timeout);
>> +??????? if (!time_left) {
>> +??????????? dev_err(&adap->dev, "msg[%d]: addr=0x%x
timeout.\n", i,
>> msgs[i].addr);
>> +??????????? ret = i;
>> +??????????? goto err_unlock_free;
>> +??????? }
>> +
>> +??????? vmsg_i = (struct virtio_i2c_msg *)virtqueue_get_buf(vq,
&len);
>> +??????? if (vmsg_i) {
>> +??????????? /* vmsg_i should point to the same address with vmsg_o */
>> +??????????? if (vmsg_i != vmsg_o) {
>> +??????????????? dev_err(&adap->dev, "msg[%d]: addr=0x%x
virtqueue
>> error.\n",
>> +??????????????????? i, vmsg_i->hdr.addr);
>> +??????????????? ret = i;
>> +??????????????? goto err_unlock_free;
>> +??????????? }
>
>
> Does this imply in order completion of i2c device?? (E.g what happens 
> if multiple virtio i2c requests are submitted)
>
> Btw, this always use a single descriptor once a time which makes me 
> suspect if a virtqueue(virtio) is really needed. It looks to me we can 
> utilize the virtqueue by submit the request in a batch.
>I'm afraid not all physical devices support batch. I'd like to keep the 
current design and consider
your suggestion as a possible optimization in the future.

Thanks.

>>
>> +}
>> +
>> +static void virtio_i2c_del_vqs(struct virtio_device *vdev)
>> +{
>> +??? vdev->config->reset(vdev);
>
>
> Why need reset here?
>
> Thanks
>I'm following what other virtio drivers do.
They reset the devices before they clean up the queues.

>
>> +??? vdev->config->del_vqs(vdev);
>> +}
>> +
>> +static int virtio_i2c_setup_vqs(struct virtio_i2c *vi)
>> +{
>> +??? struct virtio_device *vdev = vi->vdev;
>> +
>> +??? vi->vq = virtio_find_single_vq(vdev, virtio_i2c_msg_done, 
>> "i2c-msg");
>
>
> We've in the scope of ic2, so "msg" should be sufficient.
>
>OK. Will change this name. Thanks.

>> +??? return PTR_ERR_OR_ZERO(vi->vq);

Jason Wang

2020-Sep-09 09:02 UTC

head link

[PATCH] i2c: virtio: add a virtio i2c frontend driver

On 2020/9/3 ??1:34, Jie Deng wrote:> --- a/drivers/i2c/busses/Makefile
> +++ b/drivers/i2c/busses/Makefile
> @@ -6,6 +6,9 @@
>   # ACPI drivers
>   obj-$(CONFIG_I2C_SCMI)		+= i2c-scmi.o
>   
> +# VIRTIO I2C host controller driver
> +obj-$(CONFIG_I2C_VIRTIO)	+= i2c-virtio.o
> +
>   # PC SMBus host controller drivers
>   obj-$(CONFIG_I2C_ALI1535)	+= i2c-ali1535.o
>   obj-$(CONFIG_I2C_ALI1563)	+= i2c-ali1563.o
> diff --git a/drivers/i2c/busses/i2c-virtio.c
b/drivers/i2c/busses/i2c-virtio.c
> new file mode 100644
> index 0000000..47f9fd1
> --- /dev/null
> +++ b/drivers/i2c/busses/i2c-virtio.c
> @@ -0,0 +1,276 @@
> +// SPDX-License-Identifier: GPL-2.0-or-later
> +/*
> + * Virtio I2C Bus Driver
> + *
> + * Copyright (c) 2020 Intel Corporation. All rights reserved.
> + */
> +
> +#include <linux/acpi.h>
> +#include <linux/completion.h>
> +#include <linux/err.h>
> +#include <linux/i2c.h>
> +#include <linux/io.h>
> +#include <linux/jiffies.h>
> +#include <linux/kernel.h>
> +#include <linux/module.h>
> +#include <linux/platform_device.h>
> +#include <linux/wait.h>
> +
> +#include <linux/virtio.h>
> +#include <linux/virtio_ids.h>
> +#include <linux/virtio_config.h>
> +
> +#define VIRTIO_I2C_MSG_OK	0
> +#define VIRTIO_I2C_MSG_ERR	1
> +
> +/**
> + * struct virtio_i2c_hdr - the virtio I2C message header structure
> + * @addr: i2c_msg addr, the slave address
> + * @flags: i2c_msg flags
> + * @len: i2c_msg len
> + */
> +struct virtio_i2c_hdr {
> +	__virtio16 addr;
> +	__virtio16 flags;
> +	__virtio16 len;
> +} __packed;

Btw, this part should belong to uAPI, and you need to define the status 
in uAPI.

Thanks

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