media: tc358746: init m/p_best to 0

This fixes compiler warnings:

In file included from include/linux/printk.h:566,
                 from include/linux/kernel.h:29,
                 from include/linux/clk.h:13,
                 from drivers/media/i2c/tc358746.c:12:
drivers/media/i2c/tc358746.c: In function 'tc358746_find_pll_settings':
include/linux/dynamic_debug.h:272:33: warning: 'p_best' may be used uninitialized in this function [-Wmaybe-uninitialized]
  272 |         _dynamic_func_call(fmt, __dynamic_dev_dbg,              \
      |                                 ^~~~~~~~~~~~~~~~~
drivers/media/i2c/tc358746.c:817:13: note: 'p_best' was declared here
  817 |         u16 p_best, p;
      |             ^~~~~~
In file included from include/linux/printk.h:566,
                 from include/linux/kernel.h:29,
                 from include/linux/clk.h:13,
                 from drivers/media/i2c/tc358746.c:12:
include/linux/dynamic_debug.h:272:33: warning: 'm_best' may be used uninitialized in this function [-Wmaybe-uninitialized]
  272 |         _dynamic_func_call(fmt, __dynamic_dev_dbg,              \
      |                                 ^~~~~~~~~~~~~~~~~
drivers/media/i2c/tc358746.c:816:13: note: 'm_best' was declared here
  816 |         u16 m_best, mul;
      |             ^~~~~~

Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
---
 drivers/media/i2c/tc358746.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

Hi Hans,

thanks for the patch.

On 23-01-30, Hans Verkuil wrote:
> This fixes compiler warnings:
> 
> In file included from include/linux/printk.h:566,
>                  from include/linux/kernel.h:29,
>                  from include/linux/clk.h:13,
>                  from drivers/media/i2c/tc358746.c:12:
> drivers/media/i2c/tc358746.c: In function 'tc358746_find_pll_settings':
> include/linux/dynamic_debug.h:272:33: warning: 'p_best' may be used uninitialized in this function [-Wmaybe-uninitialized]
>   272 |         _dynamic_func_call(fmt, __dynamic_dev_dbg,              \
>       |                                 ^~~~~~~~~~~~~~~~~
> drivers/media/i2c/tc358746.c:817:13: note: 'p_best' was declared here
>   817 |         u16 p_best, p;
>       |             ^~~~~~
> In file included from include/linux/printk.h:566,
>                  from include/linux/kernel.h:29,
>                  from include/linux/clk.h:13,
>                  from drivers/media/i2c/tc358746.c:12:
> include/linux/dynamic_debug.h:272:33: warning: 'm_best' may be used uninitialized in this function [-Wmaybe-uninitialized]
>   272 |         _dynamic_func_call(fmt, __dynamic_dev_dbg,              \
>       |                                 ^~~~~~~~~~~~~~~~~
> drivers/media/i2c/tc358746.c:816:13: note: 'm_best' was declared here
>   816 |         u16 m_best, mul;
>       |             ^~~~~~

I'm not sure why this is printed. The m/p_best variables are only used
if best_freq != 0 else it is not used. If best_freq != 0 m/p_best is set
to the found mul/p. So IMHO this is a false positiv from the compiler.

> Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>

to make the compiler happy:

Reviewed-by: Marco Felsch <m.felsch@pengutronix.de>

Regards,
  Marco

> ---
>  drivers/media/i2c/tc358746.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/media/i2c/tc358746.c b/drivers/media/i2c/tc358746.c
> index d1f552bd81d4..b86baa5c2d82 100644
> --- a/drivers/media/i2c/tc358746.c
> +++ b/drivers/media/i2c/tc358746.c
> @@ -813,8 +813,8 @@ static unsigned long tc358746_find_pll_settings(struct tc358746 *tc358746,
>  	u32 min_delta = 0xffffffff;
>  	u16 prediv_max = 17;
>  	u16 prediv_min = 1;
> -	u16 m_best, mul;
> -	u16 p_best, p;
> +	u16 m_best = 0, mul;
> +	u16 p_best = 0, p;
>  	u8 postdiv;
> 
>  	if (fout > 1000 * HZ_PER_MHZ) {
> -- 
> 2.39.0
> 
> 
>

On 23-01-30, Hans Verkuil wrote:
> Hi Marco,
> 
> I rejected my own patch :-)
> 
> It turned out that I was testing with gcc-11 instead of 12. The latest gcc
> version doesn't report this warning.

Good to know that gcc-12 fixed this :)

Regards,
  Marco