Messages in this thread |  | | From | Jani Nikula <> | | Subject | Re: [PATCH v2 2/2] drm: ensure blend mode supported if alpha exposed | | Date | Tue, 05 May 2026 10:57:26 +0300 |
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On Mon, 04 May 2026, Leandro Ribeiro <leandro.ribeiro@collabora.com> wrote: > Before "drm/drm_blend: allow blend mode property without PREMULTI", > userspace would have to assume that only PREMULTI was supported by > drivers that didn't expose the blend mode property. But now userspace > shouldn't relly on that, as they can't count with drivers always > supporting PREMULTI. > > Error out if a driver expose alpha property or pixel formats with alpha > and does not expose the blend mode property. This way userspace don't > have to guess. Drivers that hit such error must be fixed. > > Signed-off-by: Leandro Ribeiro <leandro.ribeiro@collabora.com> > --- > drivers/gpu/drm/drm_crtc_internal.h | 1 + > drivers/gpu/drm/drm_drv.c | 7 ++++- > drivers/gpu/drm/drm_mode_config.c | 42 +++++++++++++++++++++++++++++ > 3 files changed, 49 insertions(+), 1 deletion(-) > > diff --git a/drivers/gpu/drm/drm_crtc_internal.h b/drivers/gpu/drm/drm_crtc_internal.h > index c09409229644..bdbb6b9b94ea 100644 > --- a/drivers/gpu/drm/drm_crtc_internal.h > +++ b/drivers/gpu/drm/drm_crtc_internal.h > @@ -96,6 +96,7 @@ int drm_mode_setcrtc(struct drm_device *dev, > int drm_modeset_register_all(struct drm_device *dev); > void drm_modeset_unregister_all(struct drm_device *dev); > void drm_mode_config_validate(struct drm_device *dev); > +int drm_mode_config_enforce(struct drm_device *dev); > > /* drm_modes.c */ > const char *drm_get_mode_status_name(enum drm_mode_status status); > diff --git a/drivers/gpu/drm/drm_drv.c b/drivers/gpu/drm/drm_drv.c > index 985c283cf59f..76766a370650 100644 > --- a/drivers/gpu/drm/drm_drv.c > +++ b/drivers/gpu/drm/drm_drv.c > @@ -1059,9 +1059,14 @@ int drm_dev_register(struct drm_device *dev, unsigned long flags) > const struct drm_driver *driver = dev->driver; > int ret; > > - if (!driver->load) > + if (!driver->load) { > drm_mode_config_validate(dev); > > + ret = drm_mode_config_enforce(dev);
Reading the code, I'll have no idea what "enforce" means here. Reading the function itself isn't helping either.
BR, Jani.
> + if (ret) > + return ret; > + } > + > WARN_ON(!dev->managed.final_kfree); > > if (drm_dev_needs_global_mutex(dev)) > diff --git a/drivers/gpu/drm/drm_mode_config.c b/drivers/gpu/drm/drm_mode_config.c > index 66f7dc37b597..20fd26ecb957 100644 > --- a/drivers/gpu/drm/drm_mode_config.c > +++ b/drivers/gpu/drm/drm_mode_config.c > @@ -738,3 +738,45 @@ void drm_mode_config_validate(struct drm_device *dev) > "Must have as many primary planes as there are CRTCs, but have %u primary planes and %u CRTCs", > num_primary, dev->mode_config.num_crtc); > } > + > +static int plane_require_blend_mode_for_alpha(struct drm_plane *plane) > +{ > + struct drm_device *dev = plane->dev; > + const struct drm_format_info *fmt; > + u32 i; > + > + /* blend mode property supported, no need to check anything */ > + if (plane->blend_mode_property) > + return 0; > + > + if (plane->alpha_property) { > + drm_err(dev, "[PLANE:%d:%s] alpha property exposed but blend mode not setup", > + plane->base.id, plane->name); > + return -EINVAL; > + } > + > + for (i = 0; i < plane->format_count; i++) { > + fmt = drm_format_info(plane->format_types[i]); > + if (fmt->has_alpha) { > + drm_err(dev, "[PLANE:%d:%s] pixel format with alpha exposed but blend mode not setup", > + plane->base.id, plane->name); > + return -EINVAL; > + } > + } > + > + return 0; > +} > + > +int drm_mode_config_enforce(struct drm_device *dev) > +{ > + struct drm_plane *plane; > + int ret; > + > + drm_for_each_plane(plane, dev) { > + ret = plane_require_blend_mode_for_alpha(plane); > + if (ret) > + return ret; > + } > + > + return 0; > +}
-- Jani Nikula, Intel
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