On Wednesday, October 23, 2013 5:51 PM, Johan Hovold wrote:
> On Wed, Oct 23, 2013 at 10:20:59AM +0900, Jingoo Han wrote:
> > On Wednesday, October 23, 2013 2:27 AM, Johan Hovold wrote:
> > >
> > > The driver supports 16-bit brightness values, but the value returned
> > > from get_brightness was truncated to eight bits.
> > >
> > > Cc: stable@xxxxxxxxxxxxxxx
> > > Signed-off-by: Johan Hovold <jhovold@xxxxxxxxx>
> > > ---
> > > drivers/video/backlight/atmel-pwm-bl.c | 4 ++--
> > > 1 file changed, 2 insertions(+), 2 deletions(-)
> > >
> > > diff --git a/drivers/video/backlight/atmel-pwm-bl.c b/drivers/video/backlight/atmel-pwm-bl.c
> > > index 66885fb..8aac273 100644
> > > --- a/drivers/video/backlight/atmel-pwm-bl.c
> > > +++ b/drivers/video/backlight/atmel-pwm-bl.c
> > > @@ -70,7 +70,7 @@ static int atmel_pwm_bl_set_intensity(struct backlight_device *bd)
> > > static int atmel_pwm_bl_get_intensity(struct backlight_device *bd)
> > > {
> > > struct atmel_pwm_bl *pwmbl = bl_get_data(bd);
> > > - u8 intensity;
> > > + u32 intensity;
> > >
> > > if (pwmbl->pdata->pwm_active_low) {
> > > intensity = pwm_channel_readl(&pwmbl->pwmc, PWM_CDTY) -
> > > @@ -80,7 +80,7 @@ static int atmel_pwm_bl_get_intensity(struct backlight_device *bd)
> > > pwm_channel_readl(&pwmbl->pwmc, PWM_CDTY);
> > > }
> > >
> > > - return intensity;
> > > + return (u16)intensity;
> >
> > However, atmel_pwm_bl_get_intensity() should return 'int',
> > instead of 'u16'.
>
> Yes, but the cast to int is implicit. Perhaps
>
> return (intensity & 0xffff);
>
> (or just a comment) would make it more clear why the cast is there.
>
> > Also, pwm_channel_readl() returns 'u32'.
>
> Yes, (and only the 16 least-significant bits are used). That and the
> fact that the platform-data limits are currently unsigned long (I was
> considering fixing this later) was why I preferred keeping all register
> value manipulation in u32 and do a single cast at the end.
>
> > Then, how about the following?
> >
> > --- a/drivers/video/backlight/atmel-pwm-bl.c
> > +++ b/drivers/video/backlight/atmel-pwm-bl.c
> > @@ -70,17 +70,17 @@ static int atmel_pwm_bl_set_intensity(struct backlight_device *bd)
> > static int atmel_pwm_bl_get_intensity(struct backlight_device *bd)
> > {
> > struct atmel_pwm_bl *pwmbl = bl_get_data(bd);
> > - u8 intensity;
> > + u16 intensity;
> >
> > if (pwmbl->pdata->pwm_active_low) {
> > - intensity = pwm_channel_readl(&pwmbl->pwmc, PWM_CDTY) -
> > + intensity = (u16) pwm_channel_readl(&pwmbl->pwmc, PWM_CDTY) -
> > pwmbl->pdata->pwm_duty_min;
>
> This would actually introduce a new conversion warning (unless you add
> parentheses as well) as pwm_duty_min is unsigned long. Same below.
>
> > } else {
> > - intensity = pwmbl->pdata->pwm_duty_max -
> > + intensity = (u16) pwmbl->pdata->pwm_duty_max -
> > pwm_channel_readl(&pwmbl->pwmc, PWM_CDTY);
> > }
> >
> > - return intensity;
> > + return (int)intensity;
> > }
>
> However, if you feel strongly about this, I'll respin the series (a later
> patch would likely no longer apply), use u16 and add casts to the two
> assignments.
Thank you for your kind and detailed description. :-)
OK, I have no objection on your original patch.
Would you re-send these patches with my Acked-by with CC'ing Andrew Morton,
Tomi Valkeinen? Then, these patches can be merged through mm-tree.
Best regards,
Jingoo Han
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