Nouveau - Jun 2016 - [PATCH 0/6] lib: string: add function strtolower()

This series introduces a new generic function strtolower(), which
converts strings to lowercase in-place, overwriting the original
string. This kind of functionality is needed in several places in the
kernel. Right now, everybody seems to be implementing their own copy of
this function. So, we replace several custom "strtolower"
implementations with this new library function.

Another driver that also makes use of this function 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.

This series is based on v4.7-rc5.

Markus Mayer (6):
  lib: string: add function strtolower()
  drm/nouveau/core: make use of new strtolower() function
  ACPICA: make use of new strtolower() function
  ACPI / device_sysfs: make use of new strtolower() function
  staging: speakup: replace spk_strlwr() with strtolower()
  iscsi-target: replace iscsi_initiatorname_tolower() with strtolower()

 drivers/acpi/acpica/utnonansi.c              | 13 +------------
 drivers/acpi/device_sysfs.c                  |  4 +---
 drivers/gpu/drm/nouveau/nvkm/core/firmware.c |  7 +------
 drivers/staging/speakup/kobjects.c           |  2 +-
 drivers/staging/speakup/main.c               |  2 +-
 drivers/staging/speakup/speakup.h            |  1 -
 drivers/staging/speakup/varhandlers.c        | 12 ------------
 drivers/target/iscsi/iscsi_target_nego.c     | 17 +----------------
 include/linux/string.h                       |  1 +
 lib/string.c                                 | 14 ++++++++++++++
 10 files changed, 21 insertions(+), 52 deletions(-)

-- 
2.7.4

Add a function called strtolower() to convert strings to lower case
in-place, overwriting the original string.

This seems to be a recurring requirement in the kernel that is
currently being solved by several duplicated implementations doing the
same thing.

Signed-off-by: Markus Mayer <mmayer at broadcom.com>
---
 include/linux/string.h |  1 +
 lib/string.c           | 14 ++++++++++++++
 2 files changed, 15 insertions(+)

diff --git a/include/linux/string.h b/include/linux/string.h
index 26b6f6a..aad605e 100644
--- a/include/linux/string.h
+++ b/include/linux/string.h
@@ -116,6 +116,7 @@ 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);
+char *strtolower(char *s);
 
 extern void kfree_const(const void *x);
 
diff --git a/lib/string.c b/lib/string.c
index ed83562..6e3b560 100644
--- a/lib/string.c
+++ b/lib/string.c
@@ -952,3 +952,17 @@ char *strreplace(char *s, char old, char new)
 	return s;
 }
 EXPORT_SYMBOL(strreplace);
+
+char *strtolower(char *s)
+{
+	char *p;
+
+        if (unlikely(!s))
+                return NULL;
+
+	for (p = s; *p; p++)
+		*p = tolower(*p);
+
+	return s;
+}
+EXPORT_SYMBOL(strtolower);
-- 
2.7.4

Call strtolower() rather than walking the string explicitly to convert
it to lowercase.

Signed-off-by: Markus Mayer <mmayer at broadcom.com>
---
 drivers/gpu/drm/nouveau/nvkm/core/firmware.c | 7 +------
 1 file changed, 1 insertion(+), 6 deletions(-)

diff --git a/drivers/gpu/drm/nouveau/nvkm/core/firmware.c
b/drivers/gpu/drm/nouveau/nvkm/core/firmware.c
index 34ecd4a..c50594c 100644
--- a/drivers/gpu/drm/nouveau/nvkm/core/firmware.c
+++ b/drivers/gpu/drm/nouveau/nvkm/core/firmware.c
@@ -36,16 +36,11 @@ 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]);
-	}
+	strtolower(cname);
 
 	snprintf(f, sizeof(f), "nvidia/%s/%s.bin", cname, fwname);
 	return request_firmware(fw, f, device->dev);
-- 
2.7.4

On Fri, 01 Jul 2016, Markus Mayer <mmayer at broadcom.com>
wrote:
> Add a function called strtolower() to convert strings to lower case
> in-place, overwriting the original string.
>
> This seems to be a recurring requirement in the kernel that is
> currently being solved by several duplicated implementations doing the
> same thing.
>
> Signed-off-by: Markus Mayer <mmayer at broadcom.com>
> ---
>  include/linux/string.h |  1 +
>  lib/string.c           | 14 ++++++++++++++
>  2 files changed, 15 insertions(+)
>
> diff --git a/include/linux/string.h b/include/linux/string.h
> index 26b6f6a..aad605e 100644
> --- a/include/linux/string.h
> +++ b/include/linux/string.h
> @@ -116,6 +116,7 @@ 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);
> +char *strtolower(char *s);
>  
>  extern void kfree_const(const void *x);
>  
> diff --git a/lib/string.c b/lib/string.c
> index ed83562..6e3b560 100644
> --- a/lib/string.c
> +++ b/lib/string.c
> @@ -952,3 +952,17 @@ char *strreplace(char *s, char old, char new)
>  	return s;
>  }
>  EXPORT_SYMBOL(strreplace);
> +
This needs a kernel-doc comment right here.
> +char *strtolower(char *s)
> +{
> +	char *p;
> +
> +        if (unlikely(!s))
> +                return NULL;
Using spaces for indentation? See scripts/checkpatch.pl.
> +
> +	for (p = s; *p; p++)
> +		*p = tolower(*p);
> +
> +	return s;
Why does it return a value? Could be void?

BR,
Jani.
> +}
> +EXPORT_SYMBOL(strtolower);
-- 
Jani Nikula, Intel Open Source Technology Center

On Fri, Jul 01 2016, Markus Mayer <mmayer at broadcom.com> wrote:
> Add a function called strtolower() to convert strings to lower case
> in-place, overwriting the original string.
>
> This seems to be a recurring requirement in the kernel that is
> currently being solved by several duplicated implementations doing the
> same thing.
>
> Signed-off-by: Markus Mayer <mmayer at broadcom.com>
> ---
>  include/linux/string.h |  1 +
>  lib/string.c           | 14 ++++++++++++++
>  2 files changed, 15 insertions(+)
>
> diff --git a/include/linux/string.h b/include/linux/string.h
> index 26b6f6a..aad605e 100644
> --- a/include/linux/string.h
> +++ b/include/linux/string.h
> @@ -116,6 +116,7 @@ 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);
> +char *strtolower(char *s);
>  
>  extern void kfree_const(const void *x);
>  
> diff --git a/lib/string.c b/lib/string.c
> index ed83562..6e3b560 100644
> --- a/lib/string.c
> +++ b/lib/string.c
> @@ -952,3 +952,17 @@ char *strreplace(char *s, char old, char new)
>  	return s;
>  }
>  EXPORT_SYMBOL(strreplace);
> +
> +char *strtolower(char *s)
> +{
> +	char *p;
> +
> +        if (unlikely(!s))
> +                return NULL;
> +
> +	for (p = s; *p; p++)
> +		*p = tolower(*p);
> +
> +	return s;
> +}
> +EXPORT_SYMBOL(strtolower);
A few suggestions: 

- Make the function take separate src and dst parameters, making it explicitly
  allowed to pass the same value (but not other kinds of overlap, of
  course). That way one can avoid "strcpy(dst, src);
strtolower(dst);".

- Drop the NULL check. If someone does "foo->bar = something;
  strtolower(foo->bar); put foo in a global data structure...", the
  dereference of foo->bar may happen much later. Doing the NULL deref
  sooner means it's much easier to find and fix the bug. (Also, other
  str* and mem* functions don't usually check for NULL).

- While it's true that strcpy and memcpy by definition return dst,
that's
  mostly useless. If you want it to return anything, please make it
  something that might be used - for example, having stpcpy semantics
  (returning a pointer to dst's terminating \0) means a caller might avoid
  a strlen call.

- Maybe do strtoupper while you're at it. Quick grepping didn't find any
  use for the copy-while-lowercasing, but copy-while-uppercasing can at
  least be used in drivers/acpi/acpica/nsrepair2.c,
  drivers/gpu/drm/nouveau/nvkm/engine/fifo/gk104.c,
  drivers/power/power_supply_sysfs.c along with a bunch of inplace
  uppercasing.


Rasmus

On Fri, Jul 1, 2016 at 8:50 AM, Markus Mayer <mmayer at broadcom.com>
wrote:
> Call strtolower() rather than walking the string explicitly to convert
> it to lowercase.
>
> Signed-off-by: Markus Mayer <mmayer at broadcom.com>
> ---
>  drivers/gpu/drm/nouveau/nvkm/core/firmware.c | 7 +------
>  1 file changed, 1 insertion(+), 6 deletions(-)
>
> diff --git a/drivers/gpu/drm/nouveau/nvkm/core/firmware.c
b/drivers/gpu/drm/nouveau/nvkm/core/firmware.c
> index 34ecd4a..c50594c 100644
> --- a/drivers/gpu/drm/nouveau/nvkm/core/firmware.c
> +++ b/drivers/gpu/drm/nouveau/nvkm/core/firmware.c
> @@ -36,16 +36,11 @@ 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]);
> -       }
> +       strtolower(cname);
This function doesn't seem to exist as of next-20160701, where have
you found it?

Le 01/07/2016 à 01:50, Markus Mayer a écrit :
> Add a function called strtolower() to convert strings to lower case
> in-place, overwriting the original string.
>
> This seems to be a recurring requirement in the kernel that is
> currently being solved by several duplicated implementations doing the
> same thing.
>
> Signed-off-by: Markus Mayer <mmayer at broadcom.com>
> ---
>   include/linux/string.h |  1 +
>   lib/string.c           | 14 ++++++++++++++
>   2 files changed, 15 insertions(+)
>
> diff --git a/include/linux/string.h b/include/linux/string.h
> index 26b6f6a..aad605e 100644
> --- a/include/linux/string.h
> +++ b/include/linux/string.h
> @@ -116,6 +116,7 @@ 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);
> +char *strtolower(char *s);
>   
>   extern void kfree_const(const void *x);
>   
> diff --git a/lib/string.c b/lib/string.c
> index ed83562..6e3b560 100644
> --- a/lib/string.c
> +++ b/lib/string.c
> @@ -952,3 +952,17 @@ char *strreplace(char *s, char old, char new)
>   	return s;
>   }
>   EXPORT_SYMBOL(strreplace);
> +
> +char *strtolower(char *s)
> +{
> +	char *p;
> +
> +        if (unlikely(!s))
> +                return NULL;
> +
> +	for (p = s; *p; p++)
> +		*p = tolower(*p);
> +
> +	return s;
> +}
> +EXPORT_SYMBOL(strtolower);
Why not char *strtolower(char *dest, const char *src) ? This would avoid 
multiple string iteration in what I believe is a common usage: string 
duplication than strtolower.