Michael S. Tsirkin
2021-Sep-04 20:01 UTC
[PATCH v14] i2c: virtio: add a virtio i2c frontend driver
On Fri, Jul 09, 2021 at 10:25:30AM +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. > > The device specification can be found on > https://lists.oasis-open.org/archives/virtio-comment/202101/msg00008.html. > > By following the specification, people may implement different > backend drivers to emulate different controllers according to > their needs. > > 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>Same as with qemu bits, I am confused as to what is the status of proposed spec changes and whether the driver will work with them. Let's let the dust settle on them then, then resubmit?> --- > Changes v13 -> v14 > - Put the headers in virtio_i2c.h in alphabetical order. > - Dropped I2C_FUNC_SMBUS_QUICK support. > - Dropped few unnecessary variables and checks. > - Use "num" everywhere instead of num or nr, to be consistent. > - Added few comments which make the design more clear. > > Changes v12 -> v13 > - Use _BITUL() instead of BIT(). > - Rename "virtio_i2c_send_reqs" to "virtio_i2c_prepare_reqs". > - Optimize the return value of "virtio_i2c_complete_reqs". > > Changes v11 -> v12 > - Do not sent msg_buf for zero-length request. > - Send requests to host only if all the number of transfers requested prepared successfully. > - Remove the line #include <linux/bits.h> in virtio_i2c.h. > > Changes v10 -> v11 > - Remove vi->adap.class = I2C_CLASS_DEPRECATED. > - Use #ifdef CONFIG_PM_SLEEP to replace the "__maybe_unused". > - Remove "struct mutex lock" in "struct virtio_i2c". > - Support zero-length request. > - Remove unnecessary logs. > - Remove vi->adap.timeout = HZ / 10, just use the default value. > - Use BIT(0) to define VIRTIO_I2C_FLAGS_FAIL_NEXT. > - Add the virtio_device index to adapter's naming mechanism. > > drivers/i2c/busses/Kconfig | 11 ++ > drivers/i2c/busses/Makefile | 3 + > drivers/i2c/busses/i2c-virtio.c | 285 ++++++++++++++++++++++++++++++++++++++++ > include/uapi/linux/virtio_i2c.h | 41 ++++++ > include/uapi/linux/virtio_ids.h | 1 + > 5 files changed, 341 insertions(+) > create mode 100644 drivers/i2c/busses/i2c-virtio.c > create mode 100644 include/uapi/linux/virtio_i2c.h > > diff --git a/drivers/i2c/busses/Kconfig b/drivers/i2c/busses/Kconfig > index 10acece..e47616a 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" > + select 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 69e9963..9843756 100644 > --- a/drivers/i2c/busses/Makefile > +++ b/drivers/i2c/busses/Makefile > @@ -147,4 +147,7 @@ obj-$(CONFIG_I2C_XGENE_SLIMPRO) += i2c-xgene-slimpro.o > obj-$(CONFIG_SCx200_ACB) += scx200_acb.o > obj-$(CONFIG_I2C_FSI) += i2c-fsi.o > > +# VIRTIO I2C host controller driver > +obj-$(CONFIG_I2C_VIRTIO) += i2c-virtio.o > + > ccflags-$(CONFIG_I2C_DEBUG_BUS) := -DDEBUG > diff --git a/drivers/i2c/busses/i2c-virtio.c b/drivers/i2c/busses/i2c-virtio.c > new file mode 100644 > index 0000000..0139cdc > --- /dev/null > +++ b/drivers/i2c/busses/i2c-virtio.c > @@ -0,0 +1,285 @@ > +// SPDX-License-Identifier: GPL-2.0-or-later > +/* > + * Virtio I2C Bus Driver > + * > + * The Virtio I2C Specification: > + * https://raw.githubusercontent.com/oasis-tcs/virtio-spec/master/virtio-i2c.tex > + * > + * Copyright (c) 2021 Intel Corporation. All rights reserved. > + */ > + > +#include <linux/acpi.h> > +#include <linux/completion.h> > +#include <linux/err.h> > +#include <linux/i2c.h> > +#include <linux/kernel.h> > +#include <linux/module.h> > +#include <linux/virtio.h> > +#include <linux/virtio_ids.h> > +#include <linux/virtio_config.h> > +#include <linux/virtio_i2c.h> > + > +/** > + * struct virtio_i2c - virtio I2C data > + * @vdev: virtio device for this controller > + * @completion: completion of virtio I2C message > + * @adap: I2C adapter for this controller > + * @vq: the virtio virtqueue for communication > + */ > +struct virtio_i2c { > + struct virtio_device *vdev; > + struct completion completion; > + struct i2c_adapter adap; > + struct virtqueue *vq; > +}; > + > +/** > + * struct virtio_i2c_req - the virtio I2C request structure > + * @out_hdr: the OUT header of the virtio I2C message > + * @buf: the buffer into which data is read, or from which it's written > + * @in_hdr: the IN header of the virtio I2C message > + */ > +struct virtio_i2c_req { > + struct virtio_i2c_out_hdr out_hdr ____cacheline_aligned; > + uint8_t *buf ____cacheline_aligned; > + struct virtio_i2c_in_hdr in_hdr ____cacheline_aligned; > +}; > + > +static void virtio_i2c_msg_done(struct virtqueue *vq) > +{ > + struct virtio_i2c *vi = vq->vdev->priv; > + > + complete(&vi->completion); > +} > + > +static int virtio_i2c_prepare_reqs(struct virtqueue *vq, > + struct virtio_i2c_req *reqs, > + struct i2c_msg *msgs, int num) > +{ > + struct scatterlist *sgs[3], out_hdr, msg_buf, in_hdr; > + int i; > + > + for (i = 0; i < num; i++) { > + int outcnt = 0, incnt = 0; > + > + /* > + * We don't support 0 length messages and so masked out > + * I2C_FUNC_SMBUS_QUICK in virtio_i2c_func(). > + */ > + if (!msgs[i].len) > + break; > + > + /* > + * Only 7-bit mode supported for this moment. For the address > + * format, Please check the Virtio I2C Specification. > + */ > + reqs[i].out_hdr.addr = cpu_to_le16(msgs[i].addr << 1); > + > + if (i != num - 1) > + reqs[i].out_hdr.flags = cpu_to_le32(VIRTIO_I2C_FLAGS_FAIL_NEXT); > + > + sg_init_one(&out_hdr, &reqs[i].out_hdr, sizeof(reqs[i].out_hdr)); > + sgs[outcnt++] = &out_hdr; > + > + reqs[i].buf = i2c_get_dma_safe_msg_buf(&msgs[i], 1); > + if (!reqs[i].buf) > + break; > + > + sg_init_one(&msg_buf, reqs[i].buf, msgs[i].len); > + > + if (msgs[i].flags & I2C_M_RD) > + sgs[outcnt + incnt++] = &msg_buf; > + else > + sgs[outcnt++] = &msg_buf; > + > + sg_init_one(&in_hdr, &reqs[i].in_hdr, sizeof(reqs[i].in_hdr)); > + sgs[outcnt + incnt++] = &in_hdr; > + > + if (virtqueue_add_sgs(vq, sgs, outcnt, incnt, &reqs[i], GFP_KERNEL)) { > + i2c_put_dma_safe_msg_buf(reqs[i].buf, &msgs[i], false); > + break; > + } > + } > + > + return i; > +} > + > +static int virtio_i2c_complete_reqs(struct virtqueue *vq, > + struct virtio_i2c_req *reqs, > + struct i2c_msg *msgs, int num, > + bool timedout) > +{ > + struct virtio_i2c_req *req; > + bool failed = timedout; > + unsigned int len; > + int i, j = 0; > + > + for (i = 0; i < num; i++) { > + /* Detach the ith request from the vq */ > + req = virtqueue_get_buf(vq, &len); > + > + /* > + * Condition req == &reqs[i] should always meet since we have > + * total num requests in the vq. reqs[i] can never be NULL here. > + */ > + if (!failed && (WARN_ON(req != &reqs[i]) || > + req->in_hdr.status != VIRTIO_I2C_MSG_OK)) > + failed = true; > + > + i2c_put_dma_safe_msg_buf(reqs[i].buf, &msgs[i], !failed); > + > + if (!failed) > + j++; > + } > + > + return timedout ? -ETIMEDOUT : j; > +} > + > +static int virtio_i2c_xfer(struct i2c_adapter *adap, struct i2c_msg *msgs, > + int num) > +{ > + struct virtio_i2c *vi = i2c_get_adapdata(adap); > + struct virtqueue *vq = vi->vq; > + struct virtio_i2c_req *reqs; > + unsigned long time_left; > + int count; > + > + reqs = kcalloc(num, sizeof(*reqs), GFP_KERNEL); > + if (!reqs) > + return -ENOMEM; > + > + count = virtio_i2c_prepare_reqs(vq, reqs, msgs, num); > + if (!count) > + goto err_free; > + > + /* > + * For the case where count < num, i.e. we weren't able to queue all the > + * msgs, ideally we should abort right away and return early, but some > + * of the messages are already sent to the remote I2C controller and the > + * virtqueue will be left in undefined state in that case. We kick the > + * remote here to clear the virtqueue, so we can try another set of > + * messages later on. > + */ > + > + reinit_completion(&vi->completion); > + virtqueue_kick(vq); > + > + time_left = wait_for_completion_timeout(&vi->completion, adap->timeout); > + if (!time_left) > + dev_err(&adap->dev, "virtio i2c backend timeout.\n"); > + > + count = virtio_i2c_complete_reqs(vq, reqs, msgs, count, !time_left); > + > +err_free: > + kfree(reqs); > + return count; > +} > + > +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, "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 & ~I2C_FUNC_SMBUS_QUICK); > +} > + > +static struct i2c_algorithm virtio_algorithm = { > + .master_xfer = virtio_i2c_xfer, > + .functionality = virtio_i2c_func, > +}; > + > +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; > + > + init_completion(&vi->completion); > + > + ret = virtio_i2c_setup_vqs(vi); > + if (ret) > + return ret; > + > + vi->adap.owner = THIS_MODULE; > + snprintf(vi->adap.name, sizeof(vi->adap.name), > + "i2c_virtio at virtio bus %d", vdev->index); > + vi->adap.algo = &virtio_algorithm; > + vi->adap.dev.parent = &vdev->dev; > + i2c_set_adapdata(&vi->adap, vi); > + > + /* > + * Setup ACPI node for controlled devices which will be probed through > + * ACPI. > + */ > + ACPI_COMPANION_SET(&vi->adap.dev, ACPI_COMPANION(pdev)); > + > + ret = i2c_add_adapter(&vi->adap); > + if (ret) > + 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_ADAPTER, VIRTIO_DEV_ANY_ID }, > + {} > +}; > +MODULE_DEVICE_TABLE(virtio, id_table); > + > +#ifdef CONFIG_PM_SLEEP > +static int virtio_i2c_freeze(struct virtio_device *vdev) > +{ > + virtio_i2c_del_vqs(vdev); > + return 0; > +} > + > +static int virtio_i2c_restore(struct virtio_device *vdev) > +{ > + return virtio_i2c_setup_vqs(vdev->priv); > +} > +#endif > + > +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_AUTHOR("Jie Deng <jie.deng at intel.com>"); > +MODULE_AUTHOR("Conghui Chen <conghui.chen at intel.com>"); > +MODULE_DESCRIPTION("Virtio i2c bus driver"); > +MODULE_LICENSE("GPL"); > diff --git a/include/uapi/linux/virtio_i2c.h b/include/uapi/linux/virtio_i2c.h > new file mode 100644 > index 0000000..7c6a6fc > --- /dev/null > +++ b/include/uapi/linux/virtio_i2c.h > @@ -0,0 +1,41 @@ > +/* SPDX-License-Identifier: GPL-2.0-or-later WITH Linux-syscall-note */ > +/* > + * Definitions for virtio I2C Adpter > + * > + * Copyright (c) 2021 Intel Corporation. All rights reserved. > + */ > + > +#ifndef _UAPI_LINUX_VIRTIO_I2C_H > +#define _UAPI_LINUX_VIRTIO_I2C_H > + > +#include <linux/const.h> > +#include <linux/types.h> > + > +/* The bit 0 of the @virtio_i2c_out_hdr. at flags, used to group the requests */ > +#define VIRTIO_I2C_FLAGS_FAIL_NEXT _BITUL(0) > + > +/** > + * struct virtio_i2c_out_hdr - the virtio I2C message OUT header > + * @addr: the controlled device address > + * @padding: used to pad to full dword > + * @flags: used for feature extensibility > + */ > +struct virtio_i2c_out_hdr { > + __le16 addr; > + __le16 padding; > + __le32 flags; > +}; > + > +/** > + * struct virtio_i2c_in_hdr - the virtio I2C message IN header > + * @status: the processing result from the backend > + */ > +struct virtio_i2c_in_hdr { > + __u8 status; > +}; > + > +/* The final status written by the device */ > +#define VIRTIO_I2C_MSG_OK 0 > +#define VIRTIO_I2C_MSG_ERR 1 > + > +#endif /* _UAPI_LINUX_VIRTIO_I2C_H */ > diff --git a/include/uapi/linux/virtio_ids.h b/include/uapi/linux/virtio_ids.h > index 4fe842c..3b5f05a 100644 > --- a/include/uapi/linux/virtio_ids.h > +++ b/include/uapi/linux/virtio_ids.h > @@ -55,6 +55,7 @@ > #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_ADAPTER 34 /* virtio i2c adapter */ > #define VIRTIO_ID_BT 40 /* virtio bluetooth */ > > #endif /* _LINUX_VIRTIO_IDS_H */ > -- > 2.7.4
Viresh Kumar
2021-Sep-06 04:43 UTC
[PATCH v14] i2c: virtio: add a virtio i2c frontend driver
On 04-09-21, 16:01, Michael S. Tsirkin wrote:> Same as with qemu bits, I am confused as to what is the status > of proposed spec changes and whether the driver will work > with them.This is already merged as well. The current version simply fails to transmit the messages in case the length of a buffer is 0. I have patch ready to make it work with the proposed spec changes, just waiting for them to be accepted.> Let's let the dust settle on them then, then > resubmit?It doesn't break anything for now since we don't have much users and we know zero length transfers don't work. I will submit the necessary changes once spec is finalized. -- viresh