[PATCH] drm/format-helper: Make conversion_buf_size() support sub-byte pixel fmts

[PATCH] drm/format-helper: Make conversion_buf_size() support sub-byte pixel fmts

[Javier Martinez Canillas]

There are DRM fourcc formats that have pixels smaller than a byte, but the
conversion_buf_size() function assumes that pixels are a multiple of bytes
and use the struct drm_format_info .cpp field to calculate the dst_pitch.

Instead, calculate it by using the bits per pixel (bpp) and char per pixel
(cpp) to account for formats that have sub-byte pixels.

Signed-off-by: Javier Martinez Canillas <javierm@redhat.com>
---
Tested by making sure that the following command still succeeds:

./tools/testing/kunit/kunit.py run \
--kunitconfig=drivers/gpu/drm/tests/.kunitconfig

 drivers/gpu/drm/tests/drm_format_helper_test.c | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/tests/drm_format_helper_test.c b/drivers/gpu/drm/tests/drm_format_helper_test.c
index 9536829c6e3a..f200347a1db7 100644
--- a/drivers/gpu/drm/tests/drm_format_helper_test.c
+++ b/drivers/gpu/drm/tests/drm_format_helper_test.c
@@ -409,12 +409,16 @@ static size_t conversion_buf_size(u32 dst_format, unsigned int dst_pitch,
 				  const struct drm_rect *clip)
 {
 	const struct drm_format_info *dst_fi = drm_format_info(dst_format);
+	unsigned int bpp, cpp;
 
 	if (!dst_fi)
 		return -EINVAL;
 
-	if (!dst_pitch)
-		dst_pitch = drm_rect_width(clip) * dst_fi->cpp[0];
+	if (!dst_pitch) {
+		bpp = drm_format_info_bpp(dst_fi, 0);
+		cpp = DIV_ROUND_UP(bpp, 8);
+		dst_pitch = DIV_ROUND_UP(drm_rect_width(clip) * bpp, 8);
+	}
 
 	return dst_pitch * drm_rect_height(clip);
 }
-- 
2.39.2

Re: [PATCH] drm/format-helper: Make conversion_buf_size() support sub-byte pixel fmts

[kernel test robot]

Hi Javier,

I love your patch! Perhaps something to improve:

[auto build test WARNING on drm-misc/drm-misc-next]
[also build test WARNING on linus/master v6.3-rc1 next-20230307]
[If your patch is applied to the wrong git tree, kindly drop us a note.
And when submitting patch, we suggest to use '--base' as documented in
https://git-scm.com/docs/git-format-patch#_base_tree_information]

url:    https://github.com/intel-lab-lkp/linux/commits/Javier-Martinez-Canillas/drm-format-helper-Make-conversion_buf_size-support-sub-byte-pixel-fmts/20230308-033619
base:   git://anongit.freedesktop.org/drm/drm-misc drm-misc-next
patch link:    https://lore.kernel.org/r/20230307193457.331360-1-javierm%40redhat.com
patch subject: [PATCH] drm/format-helper: Make conversion_buf_size() support sub-byte pixel fmts
config: m68k-allyesconfig (https://download.01.org/0day-ci/archive/20230308/202303080420.T1VvHVxo-lkp@intel.com/config)
compiler: m68k-linux-gcc (GCC) 12.1.0
reproduce (this is a W=1 build):
        wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross
        chmod +x ~/bin/make.cross
        # https://github.com/intel-lab-lkp/linux/commit/5f0f9d30de18661bdabebde361180893b8ddba27
        git remote add linux-review https://github.com/intel-lab-lkp/linux
        git fetch --no-tags linux-review Javier-Martinez-Canillas/drm-format-helper-Make-conversion_buf_size-support-sub-byte-pixel-fmts/20230308-033619
        git checkout 5f0f9d30de18661bdabebde361180893b8ddba27
        # save the config file
        mkdir build_dir && cp config build_dir/.config
        COMPILER_INSTALL_PATH=$HOME/0day COMPILER=gcc-12.1.0 make.cross W=1 O=build_dir ARCH=m68k olddefconfig
        COMPILER_INSTALL_PATH=$HOME/0day COMPILER=gcc-12.1.0 make.cross W=1 O=build_dir ARCH=m68k SHELL=/bin/bash drivers/gpu/

If you fix the issue, kindly add following tag where applicable
| Reported-by: kernel test robot <lkp@intel.com>
| Link: https://lore.kernel.org/oe-kbuild-all/202303080420.T1VvHVxo-lkp@intel.com/

All warnings (new ones prefixed by >>):

   drivers/gpu/drm/tests/drm_format_helper_test.c: In function 'conversion_buf_size':
>> drivers/gpu/drm/tests/drm_format_helper_test.c:412:27: warning: variable 'cpp' set but not used [-Wunused-but-set-variable]
     412 |         unsigned int bpp, cpp;
         |                           ^~~


vim +/cpp +412 drivers/gpu/drm/tests/drm_format_helper_test.c

   397	
   398	/*
   399	 * conversion_buf_size - Return the destination buffer size required to convert
   400	 * between formats.
   401	 * @dst_format: destination buffer pixel format (DRM_FORMAT_*)
   402	 * @dst_pitch: Number of bytes between two consecutive scanlines within dst
   403	 * @clip: Clip rectangle area to convert
   404	 *
   405	 * Returns:
   406	 * The size of the destination buffer or negative value on error.
   407	 */
   408	static size_t conversion_buf_size(u32 dst_format, unsigned int dst_pitch,
   409					  const struct drm_rect *clip)
   410	{
   411		const struct drm_format_info *dst_fi = drm_format_info(dst_format);
 > 412		unsigned int bpp, cpp;
   413	
   414		if (!dst_fi)
   415			return -EINVAL;
   416	
   417		if (!dst_pitch) {
   418			bpp = drm_format_info_bpp(dst_fi, 0);
   419			cpp = DIV_ROUND_UP(bpp, 8);
   420			dst_pitch = DIV_ROUND_UP(drm_rect_width(clip) * bpp, 8);
   421		}
   422	
   423		return dst_pitch * drm_rect_height(clip);
   424	}
   425	

-- 
0-DAY CI Kernel Test Service
https://github.com/intel/lkp-tests