Re: [PATCH 4/6] drm/msm: fbdev: Calculate buffer geometry with format helpers

Dmitry Baryshkov
2026-04-22T00:07:40Z

On Tue, Apr 21, 2026 at 02:51:17PM +0200, Thomas Zimmermann wrote:
> Replace the geometry and size calculation in msm's fbdev emulation
> with DRM format helpers. This consists of a 4CC lookup from the fbdev
> parameters, format lookup, pitch calculation and size calculation.
> Then allocate the GEM buffer object for the framebuffer memory from
> the calculated size.
>
> Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
> ---
> drivers/gpu/drm/msm/msm_drv.h | 7 -------
> drivers/gpu/drm/msm/msm_fbdev.c | 26 ++++++++++++--------------
> 2 files changed, 12 insertions(+), 21 deletions(-)
>
> diff --git a/drivers/gpu/drm/msm/msm_drv.h b/drivers/gpu/drm/msm/msm_drv.h
> index b3173fa4d222..00c50d7437d6 100644
> --- a/drivers/gpu/drm/msm/msm_drv.h
> +++ b/drivers/gpu/drm/msm/msm_drv.h
> @@ -509,13 +509,6 @@ void msm_hrtimer_work_init(struct msm_hrtimer_work *work,
> #define DBG(fmt, ...) DRM_DEBUG_DRIVER(fmt"\n", ##__VA_ARGS__)
> #define VERB(fmt, ...) if (0) DRM_DEBUG_DRIVER(fmt"\n", ##__VA_ARGS__)
>
> -static inline int align_pitch(int width, int bpp)
> -{
> - int bytespp = (bpp + 7) / 8;
> - /* adreno needs pitch aligned to 32 pixels: */
> - return bytespp * ALIGN(width, 32);
> -}
> -
> /* for the generated headers: */
> #define INVALID_IDX(idx) ({BUG(); 0;})
> #define fui(x) ({BUG(); 0;})
> diff --git a/drivers/gpu/drm/msm/msm_fbdev.c b/drivers/gpu/drm/msm/msm_fbdev.c
> index 1eb0368a6d07..5532c5779f17 100644
> --- a/drivers/gpu/drm/msm/msm_fbdev.c
> +++ b/drivers/gpu/drm/msm/msm_fbdev.c
> @@ -95,23 +95,25 @@ int msm_fbdev_driver_fbdev_probe(struct drm_fb_helper *helper,
> struct fb_info *fbi = helper->info;
> struct drm_mode_fb_cmd2 mode_cmd = { };
> struct drm_framebuffer *fb = NULL;
> + const struct drm_format_info *format;
> + u32 fourcc, pitch;
> + u64 size;
> struct drm_gem_object *bo;
> uint64_t paddr;
> - uint32_t format;
> - int ret, pitch;
> - int size;
> -
> - format = drm_mode_legacy_fb_format(sizes->surface_bpp, sizes->surface_depth);
> + int ret;
>
> DBG("create fbdev: %dx%d@%d (%dx%d)", sizes->surface_width,
> sizes->surface_height, sizes->surface_bpp,
> sizes->fb_width, sizes->fb_height);
>
> - pitch = align_pitch(sizes->surface_width, sizes->surface_bpp);
> + fourcc = drm_mode_legacy_fb_format(sizes->surface_bpp, sizes->surface_depth);
> + format = drm_get_format_info(dev, fourcc, DRM_FORMAT_MOD_LINEAR);
> + /* adreno needs pitch aligned to 32 pixels: */
> + pitch = drm_format_info_min_pitch(format, 0, ALIGN(sizes->surface_width, 32));
> + size = ALIGN(pitch * sizes->surface_height, PAGE_SIZE);

Hmm, why do we need to align the size to the PAGE_SIZE? I might be
missing a point, but it would be nice to mention it in the commit
message.

Other than that, LGTM.

--
With best wishes
Dmitry