Re: [PATCH 1/3] drm/omap: Pass along the format info from .fb_create() to drm_helper_mode_fill_fb_struct()

[Imre Deak <imre.deak@intel.com>]

Hi Tomi,

On Tue, Aug 05, 2025 at 02:53:36PM +0300, Tomi Valkeinen wrote:
> Hi Imre,
> 
> On 28/07/2025 13:16, Imre Deak wrote:
> > Plumb the format info from .fb_create() all the way to
> > drm_helper_mode_fill_fb_struct() to avoid the redundant
> > lookup.
> > 
> > For the fbdev case a manual drm_get_format_info() lookup
> > is needed.
> > 
> > The patch is based on the driver parts of the patchset at Link:
> > below, which missed converting the omap driver.
> > 
> > Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
> > Cc: Tomi Valkeinen <tomi.valkeinen@ideasonboard.com>
> > Cc: Thomas Zimmermann <tzimmermann@suse.de>
> > Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
> > Cc: Maxime Ripard <mripard@kernel.org>
> > Fixes: 41ab92d35ccd ("drm: Make passing of format info to drm_helper_mode_fill_fb_struct() mandatory")
> > Reported-by: Mark Brown <broonie@kernel.org>
> > Closes: https://lore.kernel.org/all/98b3a62c-91ff-4f91-a58b-e1265f84180b@sirena.org.uk
> > Link: https://lore.kernel.org/all/20250701090722.13645-1-ville.syrjala@linux.intel.com
> > Signed-off-by: Imre Deak <imre.deak@intel.com>
> > ---
> >  drivers/gpu/drm/omapdrm/omap_fb.c    | 23 ++++++++++-------------
> >  drivers/gpu/drm/omapdrm/omap_fb.h    |  2 ++
> >  drivers/gpu/drm/omapdrm/omap_fbdev.c |  5 ++++-
> >  3 files changed, 16 insertions(+), 14 deletions(-)
> > 
> > diff --git a/drivers/gpu/drm/omapdrm/omap_fb.c b/drivers/gpu/drm/omapdrm/omap_fb.c
> > index 30c81e2e5d6b3..bb3105556f193 100644
> > --- a/drivers/gpu/drm/omapdrm/omap_fb.c
> > +++ b/drivers/gpu/drm/omapdrm/omap_fb.c
> > @@ -351,7 +351,7 @@ struct drm_framebuffer *omap_framebuffer_create(struct drm_device *dev,
> >  		}
> >  	}
> >  
> > -	fb = omap_framebuffer_init(dev, mode_cmd, bos);
> > +	fb = omap_framebuffer_init(dev, info, mode_cmd, bos);
> >  	if (IS_ERR(fb))
> >  		goto error;
> >  
> > @@ -365,9 +365,9 @@ struct drm_framebuffer *omap_framebuffer_create(struct drm_device *dev,
> >  }
> >  
> >  struct drm_framebuffer *omap_framebuffer_init(struct drm_device *dev,
> > +		const struct drm_format_info *info,
> >  		const struct drm_mode_fb_cmd2 *mode_cmd, struct drm_gem_object **bos)
> >  {
> > -	const struct drm_format_info *format = NULL;
> >  	struct omap_framebuffer *omap_fb = NULL;
> >  	struct drm_framebuffer *fb = NULL;
> >  	unsigned int pitch = mode_cmd->pitches[0];
> > @@ -377,15 +377,12 @@ struct drm_framebuffer *omap_framebuffer_init(struct drm_device *dev,
> >  			dev, mode_cmd, mode_cmd->width, mode_cmd->height,
> >  			(char *)&mode_cmd->pixel_format);
> >  
> > -	format = drm_get_format_info(dev, mode_cmd->pixel_format,
> > -				     mode_cmd->modifier[0]);
> > -
> >  	for (i = 0; i < ARRAY_SIZE(formats); i++) {
> >  		if (formats[i] == mode_cmd->pixel_format)
> >  			break;
> >  	}
> >  
> > -	if (!format || i == ARRAY_SIZE(formats)) {
> > +	if (i == ARRAY_SIZE(formats)) {
> >  		dev_dbg(dev->dev, "unsupported pixel format: %4.4s\n",
> >  			(char *)&mode_cmd->pixel_format);
> >  		ret = -EINVAL;
> > @@ -399,7 +396,7 @@ struct drm_framebuffer *omap_framebuffer_init(struct drm_device *dev,
> >  	}
> >  
> >  	fb = &omap_fb->base;
> > -	omap_fb->format = format;
> > +	omap_fb->format = info;
> >  	mutex_init(&omap_fb->lock);
> >  
> >  	/*
> > @@ -407,23 +404,23 @@ struct drm_framebuffer *omap_framebuffer_init(struct drm_device *dev,
> >  	 * that the two planes of multiplane formats need the same number of
> >  	 * bytes per pixel.
> >  	 */
> > -	if (format->num_planes == 2 && pitch != mode_cmd->pitches[1]) {
> > +	if (info->num_planes == 2 && pitch != mode_cmd->pitches[1]) {
> >  		dev_dbg(dev->dev, "pitches differ between planes 0 and 1\n");
> >  		ret = -EINVAL;
> >  		goto fail;
> >  	}
> >  
> > -	if (pitch % format->cpp[0]) {
> > +	if (pitch % info->cpp[0]) {
> >  		dev_dbg(dev->dev,
> >  			"buffer pitch (%u bytes) is not a multiple of pixel size (%u bytes)\n",
> > -			pitch, format->cpp[0]);
> > +			pitch, info->cpp[0]);
> >  		ret = -EINVAL;
> >  		goto fail;
> >  	}
> >  
> > -	for (i = 0; i < format->num_planes; i++) {
> > +	for (i = 0; i < info->num_planes; i++) {
> >  		struct plane *plane = &omap_fb->planes[i];
> > -		unsigned int vsub = i == 0 ? 1 : format->vsub;
> > +		unsigned int vsub = i == 0 ? 1 : info->vsub;
> >  		unsigned int size;
> >  
> >  		size = pitch * mode_cmd->height / vsub;
> > @@ -440,7 +437,7 @@ struct drm_framebuffer *omap_framebuffer_init(struct drm_device *dev,
> >  		plane->dma_addr  = 0;
> >  	}
> >  
> > -	drm_helper_mode_fill_fb_struct(dev, fb, NULL, mode_cmd);
> > +	drm_helper_mode_fill_fb_struct(dev, fb, info, mode_cmd);
> 
> Isn't the fix really a one-liner, just passing "format" here instead of
> NULL?

That would fix the issue of fb->format being initialized to NULL yes.

However, I think the change should be in sync with the conversion of the
rest of the drivers in patchset [1]. IOW, what this patch is meant to
fix is that [1] missed converting the OMAP driver similarly to the other
drivers.

I think the change is equivalent to the above one-liner you suggest with
the following differences:

- omap_framebuffer_init() uses the drm_format_info passed down from either
  drm_internal_framebuffer_create(), or omap_fbdev_driver_fbdev_probe().
  In both cases the passed down format info matches what
  omap_framebuffer_init() would look up again.

- Skip the format == NULL check. format can't be NULL in any case, since
  that would have emitted a WARN already in drm_get_format_info() ->
  drm_format_info().

[1] https://lore.kernel.org/all/20250701090722.13645-1-ville.syrjala@linux.intel.com

>  Tomi
> 
> >  
> >  	ret = drm_framebuffer_init(dev, fb, &omap_framebuffer_funcs);
> >  	if (ret) {
> > diff --git a/drivers/gpu/drm/omapdrm/omap_fb.h b/drivers/gpu/drm/omapdrm/omap_fb.h
> > index 0873f953cf1d1..e6010302a22bd 100644
> > --- a/drivers/gpu/drm/omapdrm/omap_fb.h
> > +++ b/drivers/gpu/drm/omapdrm/omap_fb.h
> > @@ -13,6 +13,7 @@ struct drm_connector;
> >  struct drm_device;
> >  struct drm_file;
> >  struct drm_framebuffer;
> > +struct drm_format_info;
> >  struct drm_gem_object;
> >  struct drm_mode_fb_cmd2;
> >  struct drm_plane_state;
> > @@ -23,6 +24,7 @@ struct drm_framebuffer *omap_framebuffer_create(struct drm_device *dev,
> >  		struct drm_file *file, const struct drm_format_info *info,
> >  		const struct drm_mode_fb_cmd2 *mode_cmd);
> >  struct drm_framebuffer *omap_framebuffer_init(struct drm_device *dev,
> > +		const struct drm_format_info *info,
> >  		const struct drm_mode_fb_cmd2 *mode_cmd, struct drm_gem_object **bos);
> >  int omap_framebuffer_pin(struct drm_framebuffer *fb);
> >  void omap_framebuffer_unpin(struct drm_framebuffer *fb);
> > diff --git a/drivers/gpu/drm/omapdrm/omap_fbdev.c b/drivers/gpu/drm/omapdrm/omap_fbdev.c
> > index 7b63968906817..948af7ec1130b 100644
> > --- a/drivers/gpu/drm/omapdrm/omap_fbdev.c
> > +++ b/drivers/gpu/drm/omapdrm/omap_fbdev.c
> > @@ -197,7 +197,10 @@ int omap_fbdev_driver_fbdev_probe(struct drm_fb_helper *helper,
> >  		goto fail;
> >  	}
> >  
> > -	fb = omap_framebuffer_init(dev, &mode_cmd, &bo);
> > +	fb = omap_framebuffer_init(dev,
> > +				   drm_get_format_info(dev, mode_cmd.pixel_format,
> > +						       mode_cmd.modifier[0]),
> > +				   &mode_cmd, &bo);
> >  	if (IS_ERR(fb)) {
> >  		dev_err(dev->dev, "failed to allocate fb\n");
> >  		/* note: if fb creation failed, we can't rely on fb destroy
>