Nouveau - Jul 2016 - [PATCH v3 0/7] lib: string: add functions to case-convert strings

This series introduces a family of generic string case conversion
functions. This kind of functionality is needed in several places in
the kernel. Right now, everybody seems to be implementing their own
copy of this functionality.

Based on the discussion of the previous version of this series[1] and
the use cases found in the kernel, it does look like having several
flavours of case conversion functions is beneficial. The use cases fall
into three categories:
    - copying a string and converting the case while specifying a
      maximum length to mimic strlcpy()
    - copying a string and converting the case without specifying a
      length to mimic strcpy()
    - converting the case of a string in-place (i.e. modifying the
      string that was passed in)

Consequently, I am proposing these new functions:
    void strlcpytoupper(char *dst, const char *src, size_t len);
    void strlcpytolower(char *dst, const char *src, size_t len);
    void strcpytoupper(char *dst, const char *src);
    void strcpytolower(char *dst, const char *src);
    void strtoupper(char *s);
    void strtolower(char *s);

Several drivers are being modified to make use of the functions above.
Another driver that also makes use of this functionality will be
submitted upstream shortly, which prompted this whole exercise.

The changes made here have been compile-tested, but not tried out, due
to lack of required hardware.

Changes since v2:
  - use strlcpy() semantics not strncpy() semantics, i.e. guarantee
    NULL termination
  - as a result strncpyto<upper|lower> are now called
    strlcpyto<upper|lower>
  - make functions void
  - use len == -1 (SIZE_MAX) as no-limit indicator rather then len == 0
  - change PATCH 2/7 to match strlcpy() semantics
  - change PATCH 4/7 to match strlcpy() semantics

Changes since v1:
  - expanded strtolower() into a family of functions that cover use
    cases when a length argument is or isn't required and that support
    copying the string into a new buffer or changing it in-place 
  - changed the function semantics to return a pointer to the
    terminating '\0' character of the modified string
  - added strtoupper() functionality mirroring the above
  - dropped the ACPICA patch, since that code is OS independent and
    can't rely on a Linux library function (see [2])
  - Added two new patches replacing strtoupper() implementations

[1] https://lkml.org/lkml/2016/6/30/727
[2] https://lkml.org/lkml/2016/7/1/9



Markus Mayer (7):
  lib: string: add functions to case-convert strings
  drm/nouveau/core: make use of new strlcpytolower() function
  ACPI / device_sysfs: make use of new strtolower() function
  staging: speakup: replace spk_strlwr() with strlcpytolower()
  iscsi-target: replace iscsi_initiatorname_tolower() with strtolower()
  drm/nouveau/fifo/gk104: make use of new strcpytoupper() function
  power_supply: make use of new strcpytoupper() function

 drivers/acpi/device_sysfs.c                      |  4 +--
 drivers/gpu/drm/nouveau/nvkm/core/firmware.c     |  9 +-----
 drivers/gpu/drm/nouveau/nvkm/engine/fifo/gk104.c |  5 +--
 drivers/power/power_supply_sysfs.c               | 13 +++-----
 drivers/staging/speakup/kobjects.c               |  3 +-
 drivers/staging/speakup/main.c                   |  3 +-
 drivers/staging/speakup/speakup.h                |  1 -
 drivers/staging/speakup/varhandlers.c            | 12 -------
 drivers/target/iscsi/iscsi_target_nego.c         | 17 +---------
 include/linux/string.h                           | 40 ++++++++++++++++++++++++
 lib/string.c                                     | 38 ++++++++++++++++++++++
 11 files changed, 90 insertions(+), 55 deletions(-)

-- 
2.7.4

Add a collection of generic functions to convert strings to lowercase
or uppercase.

Changing the case of a string (with or without copying it first) seems
to be a recurring requirement in the kernel that is currently being
solved by several duplicated implementations doing the same thing. This
change aims at reducing this code duplication.

The new functions are
    void strlcpytoupper(char *dst, const char *src, size_t len);
    void strlcpytolower(char *dst, const char *src, size_t len);
    void strcpytoupper(char *dst, const char *src);
    void strcpytolower(char *dst, const char *src);
    void strtoupper(char *s);
    void strtolower(char *s);

The "str[l]cpyto*" versions of the function take a destination string
and a source string as arguments. The "strlcpyto*" versions
additionally
take a length argument like strlcpy() itself. Lastly, the strto*
functions take a single string argument and modify the passed-in string.

Like strlcpy(), and unlike strncpy(), the functions guarantee NULL
termination of the destination string.

Signed-off-by: Markus Mayer <mmayer at broadcom.com>
---
 include/linux/string.h | 40 ++++++++++++++++++++++++++++++++++++++++
 lib/string.c           | 38 ++++++++++++++++++++++++++++++++++++++
 2 files changed, 78 insertions(+)

diff --git a/include/linux/string.h b/include/linux/string.h
index 26b6f6a..36c9d14 100644
--- a/include/linux/string.h
+++ b/include/linux/string.h
@@ -116,6 +116,8 @@ extern void * memchr(const void *,int,__kernel_size_t);
 #endif
 void *memchr_inv(const void *s, int c, size_t n);
 char *strreplace(char *s, char old, char new);
+extern void strlcpytoupper(char *dst, const char *src, size_t len);
+extern void strlcpytolower(char *dst, const char *src, size_t len);
 
 extern void kfree_const(const void *x);
 
@@ -169,4 +171,42 @@ static inline const char *kbasename(const char *path)
 	return tail ? tail + 1 : path;
 }
 
+/**
+ * strcpytoupper - Copy string and convert to uppercase.
+ * @dst: The buffer to store the result.
+ * @src: The string to convert to uppercase.
+ */
+static inline void strcpytoupper(char *dst, const char *src)
+{
+	strlcpytoupper(dst, src, -1);
+}
+
+/**
+ * strcpytolower - Copy string and convert to lowercase.
+ * @dst: The buffer to store the result.
+ * @src: The string to convert to lowercase.
+ */
+static inline void strcpytolower(char *dst, const char *src)
+{
+	strlcpytolower(dst, src, -1);
+}
+
+/**
+ * strtoupper - Convert string to uppercase.
+ * @s: The string to operate on.
+ */
+static inline void strtoupper(char *s)
+{
+	strlcpytoupper(s, s, -1);
+}
+
+/**
+ * strtolower - Convert string to lowercase.
+ * @s: The string to operate on.
+ */
+static inline void strtolower(char *s)
+{
+	strlcpytolower(s, s, -1);
+}
+
 #endif /* _LINUX_STRING_H_ */
diff --git a/lib/string.c b/lib/string.c
index ed83562..fd8c427 100644
--- a/lib/string.c
+++ b/lib/string.c
@@ -952,3 +952,41 @@ char *strreplace(char *s, char old, char new)
 	return s;
 }
 EXPORT_SYMBOL(strreplace);
+
+/**
+ * strlcpytoupper - Copy a length-limited string and convert to uppercase.
+ * @dst: The buffer to store the result.
+ * @src: The string to convert to uppercase.
+ * @len: Maximum string length. May be SIZE_MAX (-1) to set no limit.
+ */
+void strlcpytoupper(char *dst, const char *src, size_t len)
+{
+	size_t i;
+
+	if (!len)
+		return;
+
+	for (i = 0; i < len && src[i]; ++i)
+		dst[i] = toupper(src[i]);
+	dst[i < len ? i : i - 1] = '\0';
+}
+EXPORT_SYMBOL(strlcpytoupper);
+
+/**
+ * strlcpytolower - Copy a length-limited string and convert to lowercase.
+ * @dst: The buffer to store the result.
+ * @src: The string to convert to lowercase.
+ * @len: Maximum string length. May be SIZE_MAX (-1) to set no limit.
+ */
+void strlcpytolower(char *dst, const char *src, size_t len)
+{
+	size_t i;
+
+	if (!len)
+		return;
+
+	for (i = 0; i < len && src[i]; ++i)
+		dst[i] = tolower(src[i]);
+	dst[i < len ? i : i - 1] = '\0';
+}
+EXPORT_SYMBOL(strlcpytolower);
-- 
2.7.4

Call strlcpytolower() rather than copying the string explicitly and
then walking it to convert it to lowercase.

Signed-off-by: Markus Mayer <mmayer at broadcom.com>
---

The semantics of the new function has changed, so this patch has been
updated since v2 to match the new strlcpy() semantics (no explicit NULL
terminating is required).

See https://patchwork.kernel.org/patch/9215207/ for the previous version.


 drivers/gpu/drm/nouveau/nvkm/core/firmware.c | 9 +--------
 1 file changed, 1 insertion(+), 8 deletions(-)

diff --git a/drivers/gpu/drm/nouveau/nvkm/core/firmware.c
b/drivers/gpu/drm/nouveau/nvkm/core/firmware.c
index 34ecd4a..982601e 100644
--- a/drivers/gpu/drm/nouveau/nvkm/core/firmware.c
+++ b/drivers/gpu/drm/nouveau/nvkm/core/firmware.c
@@ -36,16 +36,9 @@ nvkm_firmware_get(struct nvkm_device *device, const char
*fwname,
 {
 	char f[64];
 	char cname[16];
-	int i;
 
 	/* Convert device name to lowercase */
-	strncpy(cname, device->chip->name, sizeof(cname));
-	cname[sizeof(cname) - 1] = '\0';
-	i = strlen(cname);
-	while (i) {
-		--i;
-		cname[i] = tolower(cname[i]);
-	}
+	strlcpytolower(cname, device->chip->name, sizeof(cname));
 
 	snprintf(f, sizeof(f), "nvidia/%s/%s.bin", cname, fwname);
 	return request_firmware(fw, f, device->dev);
-- 
2.7.4

Call strcpytoupper() rather than copying the string explicitly and then
walking it to convert it to uppercase.

Signed-off-by: Markus Mayer <mmayer at broadcom.com>
---
 drivers/gpu/drm/nouveau/nvkm/engine/fifo/gk104.c | 5 +----
 1 file changed, 1 insertion(+), 4 deletions(-)

diff --git a/drivers/gpu/drm/nouveau/nvkm/engine/fifo/gk104.c
b/drivers/gpu/drm/nouveau/nvkm/engine/fifo/gk104.c
index 743f3a1..8d01032 100644
--- a/drivers/gpu/drm/nouveau/nvkm/engine/fifo/gk104.c
+++ b/drivers/gpu/drm/nouveau/nvkm/engine/fifo/gk104.c
@@ -332,10 +332,7 @@ gk104_fifo_intr_fault(struct gk104_fifo *fifo, int unit)
 		enum nvkm_devidx engidx = nvkm_top_fault(device->top, unit);
 		if (engidx < NVKM_SUBDEV_NR) {
 			const char *src = nvkm_subdev_name[engidx];
-			char *dst = en;
-			do {
-				*dst++ = toupper(*src++);
-			} while(*src);
+			strcpytoupper(en, src);
 			engine = nvkm_device_engine(device, engidx);
 		}
 	} else {
-- 
2.7.4

On 08/07/16 23:43, Markus Mayer wrote:
> Add a collection of generic functions to convert strings to lowercase
> or uppercase.
> 
> Changing the case of a string (with or without copying it first) seems
> to be a recurring requirement in the kernel that is currently being
> solved by several duplicated implementations doing the same thing. This
> change aims at reducing this code duplication.
> 
> The new functions are
>     void strlcpytoupper(char *dst, const char *src, size_t len);
>     void strlcpytolower(char *dst, const char *src, size_t len);
>     void strcpytoupper(char *dst, const char *src);
>     void strcpytolower(char *dst, const char *src);
>     void strtoupper(char *s);
>     void strtolower(char *s);
> 
> The "str[l]cpyto*" versions of the function take a destination
string
> and a source string as arguments. The "strlcpyto*" versions
additionally
> take a length argument like strlcpy() itself. Lastly, the strto*
> functions take a single string argument and modify the passed-in string.
> 
> Like strlcpy(), and unlike strncpy(), the functions guarantee NULL
> termination of the destination string.
> 
> Signed-off-by: Markus Mayer <mmayer at broadcom.com>
> ---
>  include/linux/string.h | 40 ++++++++++++++++++++++++++++++++++++++++
>  lib/string.c           | 38 ++++++++++++++++++++++++++++++++++++++
>  2 files changed, 78 insertions(+)
> 
> diff --git a/include/linux/string.h b/include/linux/string.h
> index 26b6f6a..36c9d14 100644
> --- a/include/linux/string.h
> +++ b/include/linux/string.h
> @@ -116,6 +116,8 @@ extern void * memchr(const void *,int,__kernel_size_t);
>  #endif
>  void *memchr_inv(const void *s, int c, size_t n);
>  char *strreplace(char *s, char old, char new);
> +extern void strlcpytoupper(char *dst, const char *src, size_t len);
> +extern void strlcpytolower(char *dst, const char *src, size_t len);
>  
>  extern void kfree_const(const void *x);
>  
> @@ -169,4 +171,42 @@ static inline const char *kbasename(const char *path)
>  	return tail ? tail + 1 : path;
>  }
>  
> +/**
> + * strcpytoupper - Copy string and convert to uppercase.
> + * @dst: The buffer to store the result.
> + * @src: The string to convert to uppercase.
> + */
> +static inline void strcpytoupper(char *dst, const char *src)
> +{
> +	strlcpytoupper(dst, src, -1);
> +}
> +
Why not use SIZE_MAX instead of -1?
> +/**
> + * strcpytolower - Copy string and convert to lowercase.
> + * @dst: The buffer to store the result.
> + * @src: The string to convert to lowercase.
> + */
> +static inline void strcpytolower(char *dst, const char *src)
> +{
> +	strlcpytolower(dst, src, -1);
> +}
> +
Same here, and the 2 below :)

Thanks Markus,
Luis
> +/**
> + * strtoupper - Convert string to uppercase.
> + * @s: The string to operate on.
> + */
> +static inline void strtoupper(char *s)
> +{
> +	strlcpytoupper(s, s, -1);
> +}
> +
> +/**
> + * strtolower - Convert string to lowercase.
> + * @s: The string to operate on.
> + */
> +static inline void strtolower(char *s)
> +{
> +	strlcpytolower(s, s, -1);
> +}
> +
>  #endif /* _LINUX_STRING_H_ */
> diff --git a/lib/string.c b/lib/string.c
> index ed83562..fd8c427 100644
> --- a/lib/string.c
> +++ b/lib/string.c
> @@ -952,3 +952,41 @@ char *strreplace(char *s, char old, char new)
>  	return s;
>  }
>  EXPORT_SYMBOL(strreplace);
> +
> +/**
> + * strlcpytoupper - Copy a length-limited string and convert to uppercase.
> + * @dst: The buffer to store the result.
> + * @src: The string to convert to uppercase.
> + * @len: Maximum string length. May be SIZE_MAX (-1) to set no limit.
> + */
> +void strlcpytoupper(char *dst, const char *src, size_t len)
> +{
> +	size_t i;
> +
> +	if (!len)
> +		return;
> +
> +	for (i = 0; i < len && src[i]; ++i)
> +		dst[i] = toupper(src[i]);
> +	dst[i < len ? i : i - 1] = '\0';
> +}
> +EXPORT_SYMBOL(strlcpytoupper);
> +
> +/**
> + * strlcpytolower - Copy a length-limited string and convert to lowercase.
> + * @dst: The buffer to store the result.
> + * @src: The string to convert to lowercase.
> + * @len: Maximum string length. May be SIZE_MAX (-1) to set no limit.
> + */
> +void strlcpytolower(char *dst, const char *src, size_t len)
> +{
> +	size_t i;
> +
> +	if (!len)
> +		return;
> +
> +	for (i = 0; i < len && src[i]; ++i)
> +		dst[i] = tolower(src[i]);
> +	dst[i < len ? i : i - 1] = '\0';
> +}
> +EXPORT_SYMBOL(strlcpytolower);
>

On 7/8/2016 6:43 PM, Markus Mayer wrote:
> This series introduces a family of generic string case conversion
> functions. This kind of functionality is needed in several places in
> the kernel. Right now, everybody seems to be implementing their own
> copy of this functionality.
>
> Based on the discussion of the previous version of this series[1] and
> the use cases found in the kernel, it does look like having several
> flavours of case conversion functions is beneficial. The use cases fall
> into three categories:
>      - copying a string and converting the case while specifying a
>        maximum length to mimic strlcpy()
>      - copying a string and converting the case without specifying a
>        length to mimic strcpy()
>      - converting the case of a string in-place (i.e. modifying the
>        string that was passed in)
>
> Consequently, I am proposing these new functions:
>      void strlcpytoupper(char *dst, const char *src, size_t len);
>      void strlcpytolower(char *dst, const char *src, size_t len);
>      void strcpytoupper(char *dst, const char *src);
>      void strcpytolower(char *dst, const char *src);
>      void strtoupper(char *s);
>      void strtolower(char *s);
You may want to read the article here:

https://lwn.net/Articles/659214/

and follow up some of the discussion threads on LKML about the best
semantics to advertise for the strlcpy/strscpy variants.  It might be
helpful to return some kind of overflow/truncation error from your
copy functions so people can error-check the result.

-- 
Chris Metcalf, Mellanox Technologies
http://www.mellanox.com

On 9 July 2016 at 20:13, Chris Metcalf <cmetcalf at mellanox.com>
wrote:
> On 7/8/2016 6:43 PM, Markus Mayer wrote:
>>
>> This series introduces a family of generic string case conversion
>> functions. This kind of functionality is needed in several places in
>> the kernel. Right now, everybody seems to be implementing their own
>> copy of this functionality.
>>
>> Based on the discussion of the previous version of this series[1] and
>> the use cases found in the kernel, it does look like having several
>> flavours of case conversion functions is beneficial. The use cases fall
>> into three categories:
>>      - copying a string and converting the case while specifying a
>>        maximum length to mimic strlcpy()
>>      - copying a string and converting the case without specifying a
>>        length to mimic strcpy()
>>      - converting the case of a string in-place (i.e. modifying the
>>        string that was passed in)
>>
>> Consequently, I am proposing these new functions:
>>      void strlcpytoupper(char *dst, const char *src, size_t len);
>>      void strlcpytolower(char *dst, const char *src, size_t len);
>>      void strcpytoupper(char *dst, const char *src);
>>      void strcpytolower(char *dst, const char *src);
>>      void strtoupper(char *s);
>>      void strtolower(char *s);
>
>
> You may want to read the article here:
>
> https://lwn.net/Articles/659214/
I'll read that. Thanks.
> and follow up some of the discussion threads on LKML about the best
> semantics to advertise for the strlcpy/strscpy variants.  It might be
> helpful to return some kind of overflow/truncation error from your
> copy functions so people can error-check the result.
I am inclined to agree. However, everybody has been telling me that
these functions should be void. Originally they weren't.

Regards,
-Markus