On Fri, 8 Mar 2013 14:31:07 -0500 Devendra Naga <devendra.aaru@xxxxxxxxx> wrote:
> while compiling with make W=1 (gcc gcc (GCC) 4.7.2 20121109 (Red Hat 4.7.2-8))
>
> found the following warning
>
> drivers/video/backlight/adp5520_bl.c: In function ___adp5520_show___:
> drivers/video/backlight/adp5520_bl.c:146:6: warning: variable ___error___ set but not used [-Wunused-but-set-variable]
>
> fixed by removing the variable
>
> ...
>
> --- a/drivers/video/backlight/adp5520_bl.c
> +++ b/drivers/video/backlight/adp5520_bl.c
> @@ -143,11 +143,10 @@ static int adp5520_bl_setup(struct backlight_device *bl)
> static ssize_t adp5520_show(struct device *dev, char *buf, int reg)
> {
> struct adp5520_bl *data = dev_get_drvdata(dev);
> - int error;
> uint8_t reg_val;
>
> mutex_lock(&data->lock);
> - error = adp5520_read(data->master, reg, ®_val);
> + adp5520_read(data->master, reg, ®_val);
> mutex_unlock(&data->lock);
>
> return sprintf(buf, "%u\n", reg_val);
We shouldn't just ignore the error; with the code as it stands, a
adp5520_read() failure will result in the kernel displaying
uninitialised garbage.
So it would be better to propagate the adp5520_read() return value back
to the caller if it's negative.
(This assumes that the i2c layer returns a sane return value - if it
does, that would make i2c pretty unique :( We could get paranoid and
return a hard-wired -EIO, but it would be bad of us to overwrite things
like -ENOMEM).
So I'd suggest this:
--- a/drivers/video/backlight/adp5520_bl.c~video-backlight-adp5520-fix-compiler-warning-in-adp5520_show
+++ a/drivers/video/backlight/adp5520_bl.c
@@ -143,13 +143,15 @@ static int adp5520_bl_setup(struct backl
static ssize_t adp5520_show(struct device *dev, char *buf, int reg)
{
struct adp5520_bl *data = dev_get_drvdata(dev);
- int error;
+ int ret;
uint8_t reg_val;
mutex_lock(&data->lock);
- error = adp5520_read(data->master, reg, ®_val);
+ ret = adp5520_read(data->master, reg, ®_val);
mutex_unlock(&data->lock);
+ if (ret < 0)
+ return ret;
return sprintf(buf, "%u\n", reg_val);
}
_
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