linux-kernel - Re: [PATCH] media: ov9650: avoid maybe-uninitialized warnings

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Message-ID: <CAC5umygy=BBSF_v_vVNnrZ9_1LCpJW0V212yxVqmGUUF-kOOSA@mail.gmail.com>
Date:   Thu, 27 Sep 2018 00:49:37 +0900
From:   Akinobu Mita <akinobu.mita@...il.com>
To:     Arnd Bergmann <arnd@...db.de>
Cc:     Sakari Ailus <sakari.ailus@...ux.intel.com>,
        Mauro Carvalho Chehab <mchehab@...nel.org>,
        Sylwester Nawrocki <s.nawrocki@...sung.com>,
        Hans Verkuil <hans.verkuil@...co.com>,
        wsa+renesas@...g-engineering.com, gustavo@...eddedor.com,
        linux-media@...r.kernel.org, LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] media: ov9650: avoid maybe-uninitialized warnings

2018年9月26日(水) 21:51 Arnd Bergmann <arnd@...db.de>:
>
> The regmap change causes multiple warnings like
>
> drivers/media/i2c/ov9650.c: In function 'ov965x_g_volatile_ctrl':
> drivers/media/i2c/ov9650.c:889:29: error: 'reg2' may be used uninitialized in this function [-Werror=maybe-uninitialized]
>    exposure = ((reg2 & 0x3f) << 10) | (reg1 << 2) |
>               ~~~~~~~~~~~~~~~^~~~~~
>
> It is apparently hard for the compiler to see here if ov965x_read()
> returned successfully or not. Besides, we have a v4l2_dbg() statement
> that prints an uninitialized value if regmap_read() fails.
>
> Adding an 'else' clause avoids the ambiguity.
>
> Fixes: 361f3803adfe ("media: ov9650: use SCCB regmap")
> Signed-off-by: Arnd Bergmann <arnd@...db.de>

Looks good.

Reviewed-by: Akinobu Mita <akinobu.mita@...il.com>

> ---
>  drivers/media/i2c/ov9650.c | 2 ++
>  1 file changed, 2 insertions(+)
>
> diff --git a/drivers/media/i2c/ov9650.c b/drivers/media/i2c/ov9650.c
> index 3c9e6798d14b..77944da31de1 100644
> --- a/drivers/media/i2c/ov9650.c
> +++ b/drivers/media/i2c/ov9650.c
> @@ -433,6 +433,8 @@ static int ov965x_read(struct ov965x *ov965x, u8 addr, u8 *val)
>         ret = regmap_read(ov965x->regmap, addr, &buf);
>         if (!ret)
>                 *val = buf;
> +        else
> +                *val = -1;
>
>         v4l2_dbg(2, debug, &ov965x->sd, "%s: 0x%02x @ 0x%02x. (%d)\n",
>                  __func__, *val, addr, ret);
> --
> 2.18.0
>