linux-kernel - Re: [PATCH 14/14] [media] fix warning on v4l2_subdev

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Message-ID: <20170714124132.u3fzpetbh3b7gj7f@mwanda>
Date:   Fri, 14 Jul 2017 15:41:32 +0300
From:   Dan Carpenter <dan.carpenter@...cle.com>
To:     Arnd Bergmann <arnd@...db.de>
Cc:     linux-kernel@...r.kernel.org,
        Mauro Carvalho Chehab <mchehab@...nel.org>,
        Hans Verkuil <hverkuil@...all.nl>, devel@...verdev.osuosl.org,
        Niklas Söderlund 
        <niklas.soderlund@...natech.se>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Robert Jarzmik <robert.jarzmik@...e.fr>,
        adi-buildroot-devel@...ts.sourceforge.net,
        dri-devel@...ts.freedesktop.org, linux-renesas-soc@...r.kernel.org,
        linux-ide@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        Tejun Heo <tj@...nel.org>, akpm@...ux-foundation.org,
        Alan Cox <alan@...ux.intel.com>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Daeseok Youn <daeseok.youn@...il.com>,
        Guenter Roeck <linux@...ck-us.net>, linux-media@...r.kernel.org
Subject: Re: [PATCH 14/14] [media] fix warning on v4l2_subdev_call() result
 interpreted as bool

On Fri, Jul 14, 2017 at 11:36:56AM +0200, Arnd Bergmann wrote:
> @@ -1158,7 +1158,8 @@ static void ccdc_configure(struct isp_ccdc_device *ccdc)
>  	 */
>  	fmt_src.pad = pad->index;
>  	fmt_src.which = V4L2_SUBDEV_FORMAT_ACTIVE;
> -	if (!v4l2_subdev_call(sensor, pad, get_fmt, NULL, &fmt_src)) {
> +	ret = v4l2_subdev_call(sensor, pad, get_fmt, NULL, &fmt_src);
> +	if (!ret) {
>  		fmt_info = omap3isp_video_format_info(fmt_src.format.code);
>  		depth_in = fmt_info->width;
>  	}

Is the original code buggy?

media/platform/omap3isp/ispccdc.c
  1156          /* Compute the lane shifter shift value and enable the bridge when the
  1157           * input format is a non-BT.656 YUV variant.
  1158           */
  1159          fmt_src.pad = pad->index;
  1160          fmt_src.which = V4L2_SUBDEV_FORMAT_ACTIVE;
  1161          if (!v4l2_subdev_call(sensor, pad, get_fmt, NULL, &fmt_src)) {
  1162                  fmt_info = omap3isp_video_format_info(fmt_src.format.code);
  1163                  depth_in = fmt_info->width;
  1164          }

If v4l2_subdev_call() then depth_in is zero.

  1165  
  1166          fmt_info = omap3isp_video_format_info(format->code);
  1167          depth_out = fmt_info->width;
  1168          shift = depth_in - depth_out;
                ^^^^^^^^^^^^^^^^^^^^^^^^^^^^

How do we know that this subtraction doesn't set "shift" to a very high
positive?

  1169  
  1170          if (ccdc->bt656)
  1171                  bridge = ISPCTRL_PAR_BRIDGE_DISABLE;
  1172          else if (fmt_info->code == MEDIA_BUS_FMT_YUYV8_2X8)
  1173                  bridge = ISPCTRL_PAR_BRIDGE_LENDIAN;
  1174          else if (fmt_info->code == MEDIA_BUS_FMT_UYVY8_2X8)
  1175                  bridge = ISPCTRL_PAR_BRIDGE_BENDIAN;
  1176          else
  1177                  bridge = ISPCTRL_PAR_BRIDGE_DISABLE;
  1178  
  1179          omap3isp_configure_bridge(isp, ccdc->input, parcfg, shift, bridge);

regards,
dan carpenter