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SubjectRe: [PATCH 4/6] drivers/acpi: Use kasprintf
On Wed, 10 Mar 2010 22:16:51 +0100 (CET)
Julia Lawall <julia@diku.dk> wrote:

> From: Julia Lawall <julia@diku.dk>
>
> kasprintf combines kmalloc and sprintf, and takes care of the size
> calculation itself.
>
> The semantic patch that makes this change is as follows:
> (http://coccinelle.lip6.fr/)
>
> // <smpl>
> @@
> expression a,flag;
> expression list args;
> statement S;
> @@
>
> a =
> - \(kmalloc\|kzalloc\)(...,flag)
> + kasprintf(flag,args)
> <... when != a
> if (a == NULL || ...) S
> ...>
> - sprintf(a,args);
> // </smpl>
>
> Signed-off-by: Julia Lawall <julia@diku.dk>
>
> ---
> drivers/acpi/video.c | 6 ++----
> 1 file changed, 2 insertions(+), 4 deletions(-)
>
> diff -u -p a/drivers/acpi/video.c b/drivers/acpi/video.c
> --- a/drivers/acpi/video.c
> +++ b/drivers/acpi/video.c
> @@ -1005,11 +1005,10 @@ static void acpi_video_device_find_cap(s
> result = acpi_video_init_brightness(device);
> if (result)
> return;
> - name = kzalloc(MAX_NAME_LEN, GFP_KERNEL);
> + name = kasprintf(GFP_KERNEL, "acpi_video%d", count++);
> if (!name)
> return;
>
> - sprintf(name, "acpi_video%d", count++);
> device->backlight = backlight_device_register(name,
> NULL, device, &acpi_backlight_ops);
> kfree(name);
> @@ -1056,10 +1055,9 @@ static void acpi_video_device_find_cap(s
> if (device->cap._DCS && device->cap._DSS) {
> static int count;
> char *name;
> - name = kzalloc(MAX_NAME_LEN, GFP_KERNEL);
> + name = kasprintf(GFP_KERNEL, "acpi_video%d", count++);
> if (!name)
> return;
> - sprintf(name, "acpi_video%d", count++);
> device->output_dev = video_output_register(name,
> NULL, device, &acpi_output_properties);
> kfree(name);

It's not an equivalent change - if the memory allocation fails, this
patch will now cause `count' to be incremented anyway, presumably
leaving a gap in the enumeration.

I don't know if that matters. If so, this:

--- a/drivers/acpi/video.c~drivers-acpi-use-kasprintf-fix
+++ a/drivers/acpi/video.c
@@ -1006,9 +1006,10 @@ static void acpi_video_device_find_cap(s
result = acpi_video_init_brightness(device);
if (result)
return;
- name = kasprintf(GFP_KERNEL, "acpi_video%d", count++);
+ name = kasprintf(GFP_KERNEL, "acpi_video%d", count);
if (!name)
return;
+ count++;

memset(&props, 0, sizeof(struct backlight_properties));
props.max_brightness = device->brightness->count - 3;
@@ -1058,9 +1059,10 @@ static void acpi_video_device_find_cap(s
if (device->cap._DCS && device->cap._DSS) {
static int count;
char *name;
- name = kasprintf(GFP_KERNEL, "acpi_video%d", count++);
+ name = kasprintf(GFP_KERNEL, "acpi_video%d", count);
if (!name)
return;
+ count++;
device->output_dev = video_output_register(name,
NULL, device, &acpi_output_properties);
kfree(name);
_


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