Re: [PATCH v2] drm/vkms: Remove index parameter from init_vkms_output

["José Expósito" <jose.exposito89@gmail.com>]

> On 26/10/24 - 12:22, Maíra Canal wrote:
> > Hi Louis,
> > 
> > On 10/10/24 14:27, Louis Chauvet wrote:
> > > VKMS currently supports only one CRTC, so it make no sense to have this
> > > index configurable. To avoid issues, replace this hardcoded index by
> > > drm_crtc_mask when applicable.
> > > 
> > > There is no need to manually set a crtc mask on primary and cursor plane
> > > as it is automatically set by drmm_crtc_alloc_with_planes.
> > > 
> > > In addition, this will remove the use of an uninitialized structure in
> > > vkms_add_overlay_plane. This currently works by chance because two things:
> > > - vkms_plane_init always set a possible_crtcs value, so the problematic
> > >    branch is never used;
> > > - drm_crtc_mask on an kzalloc'd drm_crtc returns BIT(0), and the VKMS CRTC
> > >    always have this id.
> > > 
> > > Signed-off-by: Louis Chauvet <louis.chauvet@bootlin.com>
> > > ---
> > > Changes in v2:
> > > - Applied comments from José
> > > - Link to v1: https://lore.kernel.org/r/20240906-vkms-remove-index-v1-1-3cfedd8ccb2f@bootlin.com
> > > ---
> > >   drivers/gpu/drm/vkms/vkms_drv.c    |  2 +-
> > >   drivers/gpu/drm/vkms/vkms_drv.h    |  8 ++----
> > >   drivers/gpu/drm/vkms/vkms_output.c | 54 ++++++++++++++------------------------
> > >   drivers/gpu/drm/vkms/vkms_plane.c  |  4 +--
> > >   4 files changed, 24 insertions(+), 44 deletions(-)
> > > 
> > > diff --git a/drivers/gpu/drm/vkms/vkms_drv.c b/drivers/gpu/drm/vkms/vkms_drv.c
> > > index 2d1e95cb66e5..0f6805b9fe7b 100644
> > > --- a/drivers/gpu/drm/vkms/vkms_drv.c
> > > +++ b/drivers/gpu/drm/vkms/vkms_drv.c
> > > @@ -174,7 +174,7 @@ static int vkms_modeset_init(struct vkms_device *vkmsdev)
> > >   	dev->mode_config.preferred_depth = 0;
> > >   	dev->mode_config.helper_private = &vkms_mode_config_helpers;
> > > -	return vkms_output_init(vkmsdev, 0);
> > > +	return vkms_output_init(vkmsdev);
> > >   }
> > >   static int vkms_create(struct vkms_config *config)
> > > diff --git a/drivers/gpu/drm/vkms/vkms_drv.h b/drivers/gpu/drm/vkms/vkms_drv.h
> > > index 672fe191e239..036101ee4ea1 100644
> > > --- a/drivers/gpu/drm/vkms/vkms_drv.h
> > > +++ b/drivers/gpu/drm/vkms/vkms_drv.h
> > > @@ -212,21 +212,17 @@ int vkms_crtc_init(struct drm_device *dev, struct drm_crtc *crtc,
> > >    * vkms_output_init() - Initialize all sub-components needed for a VKMS device.
> > >    *
> > >    * @vkmsdev: VKMS device to initialize
> > > - * @index: CRTC which can be attached to the planes. The caller must ensure that
> > > - *	   @index is positive and less or equals to 31.
> > >    */
> > > -int vkms_output_init(struct vkms_device *vkmsdev, int index);
> > > +int vkms_output_init(struct vkms_device *vkmsdev);
> > >   /**
> > >    * vkms_plane_init() - Initialize a plane
> > >    *
> > >    * @vkmsdev: VKMS device containing the plane
> > >    * @type: type of plane to initialize
> > > - * @index: CRTC which can be attached to the plane. The caller must ensure that
> > > - *	   @index is positive and less or equals to 31.
> > >    */
> > >   struct vkms_plane *vkms_plane_init(struct vkms_device *vkmsdev,
> > > -				   enum drm_plane_type type, int index);
> > > +				   enum drm_plane_type type);
> > >   /* CRC Support */
> > >   const char *const *vkms_get_crc_sources(struct drm_crtc *crtc,
> > > diff --git a/drivers/gpu/drm/vkms/vkms_output.c b/drivers/gpu/drm/vkms/vkms_output.c
> > > index 0a5a185aa0b0..5128aa3b2eb6 100644
> > > --- a/drivers/gpu/drm/vkms/vkms_output.c
> > > +++ b/drivers/gpu/drm/vkms/vkms_output.c
> > > @@ -32,29 +32,14 @@ static const struct drm_connector_helper_funcs vkms_conn_helper_funcs = {
> > >   	.get_modes    = vkms_conn_get_modes,
> > >   };
> > > -static int vkms_add_overlay_plane(struct vkms_device *vkmsdev, int index,
> > > -				  struct drm_crtc *crtc)
> > > -{
> > > -	struct vkms_plane *overlay;
> > > -
> > > -	overlay = vkms_plane_init(vkmsdev, DRM_PLANE_TYPE_OVERLAY, index);
> > > -	if (IS_ERR(overlay))
> > > -		return PTR_ERR(overlay);
> > > -
> > > -	if (!overlay->base.possible_crtcs)
> > > -		overlay->base.possible_crtcs = drm_crtc_mask(crtc);
> > > -
> > > -	return 0;
> > > -}
> > > -
> > > -int vkms_output_init(struct vkms_device *vkmsdev, int index)
> > > +int vkms_output_init(struct vkms_device *vkmsdev)
> > >   {
> > >   	struct vkms_output *output = &vkmsdev->output;
> > >   	struct drm_device *dev = &vkmsdev->drm;
> > >   	struct drm_connector *connector = &output->connector;
> > >   	struct drm_encoder *encoder = &output->encoder;
> > >   	struct drm_crtc *crtc = &output->crtc;
> > > -	struct vkms_plane *primary, *cursor = NULL;
> > > +	struct vkms_plane *primary, *overlay, *cursor = NULL;
> > >   	int ret;
> > >   	int writeback;
> > >   	unsigned int n;
> > > @@ -65,34 +50,37 @@ int vkms_output_init(struct vkms_device *vkmsdev, int index)
> > >   	 * The overlay and cursor planes are not mandatory, but can be used to perform complex
> > >   	 * composition.
> > >   	 */
> > > -	primary = vkms_plane_init(vkmsdev, DRM_PLANE_TYPE_PRIMARY, index);
> > > +	primary = vkms_plane_init(vkmsdev, DRM_PLANE_TYPE_PRIMARY);
> > >   	if (IS_ERR(primary))
> > >   		return PTR_ERR(primary);
> > > -	if (vkmsdev->config->overlay) {
> > > -		for (n = 0; n < NUM_OVERLAY_PLANES; n++) {
> > > -			ret = vkms_add_overlay_plane(vkmsdev, index, crtc);
> > > -			if (ret)
> > > -				return ret;
> > > -		}
> > > -	}
> > > -
> > >   	if (vkmsdev->config->cursor) {
> > > -		cursor = vkms_plane_init(vkmsdev, DRM_PLANE_TYPE_CURSOR, index);
> > > +		cursor = vkms_plane_init(vkmsdev, DRM_PLANE_TYPE_CURSOR);
> > >   		if (IS_ERR(cursor))
> > >   			return PTR_ERR(cursor);
> > >   	}
> > > -	/* [1]: Allocation of a CRTC, its index will be BIT(0) = 1 */
> > >   	ret = vkms_crtc_init(dev, crtc, &primary->base, &cursor->base);
> > >   	if (ret)
> > >   		return ret;
> > > +	if (vkmsdev->config->overlay) {
> > > +		for (n = 0; n < NUM_OVERLAY_PLANES; n++) {
> > > +			overlay = vkms_plane_init(vkmsdev, DRM_PLANE_TYPE_OVERLAY);
> > > +			if (IS_ERR(overlay)) {
> > > +				DRM_DEV_ERROR(dev->dev, "Failed to init vkms plane\n");
> > > +				ret = PTR_ERR(overlay);
> > > +				goto err_crtc;
> > > +			}
> > > +			overlay->base.possible_crtcs = drm_crtc_mask(crtc);
> > > +		}
> > > +	}
> > > +
> > >   	ret = drm_connector_init(dev, connector, &vkms_connector_funcs,
> > >   				 DRM_MODE_CONNECTOR_VIRTUAL);
> > >   	if (ret) {
> > >   		DRM_ERROR("Failed to init connector\n");
> > > -		goto err_connector;
> > > +		goto err_crtc;
> > >   	}
> > >   	drm_connector_helper_add(connector, &vkms_conn_helper_funcs);
> > > @@ -103,11 +91,7 @@ int vkms_output_init(struct vkms_device *vkmsdev, int index)
> > >   		DRM_ERROR("Failed to init encoder\n");
> > >   		goto err_encoder;
> > >   	}
> > > -	/*
> > > -	 * This is a hardcoded value to select crtc for the encoder.
> > > -	 * BIT(0) here designate the first registered CRTC, the one allocated in [1]
> > > -	 */
> > > -	encoder->possible_crtcs = BIT(0);
> > > +	encoder->possible_crtcs = drm_crtc_mask(crtc);
> > >   	ret = drm_connector_attach_encoder(connector, encoder);
> > >   	if (ret) {
> > > @@ -131,7 +115,7 @@ int vkms_output_init(struct vkms_device *vkmsdev, int index)
> > >   err_encoder:
> > >   	drm_connector_cleanup(connector);
> > > -err_connector:
> > > +err_crtc:
> > >   	drm_crtc_cleanup(crtc);
> > 
> > Do we really need `drm_crtc_cleanup`? We are allocating the CRTC with
> > `drmm_crtc_init_with_planes`.
> 
> I agree, I'll check the previous discussions I've had on the mailing list, 
> I have a little doubt that someone asked me to re-add this cleaning at 
> some point.

Oh! Good point. It looks like drm_crtc_cleanup() is a leftover from
commit 99cc528ebe92 ("drm/vkms: Use drmm_crtc_init_with_planes()").

Since the previous code in vkms_output.c was calling drm_crtc_cleanup()
I assumed it was required. But Maíra is right, it is safe to drop it.

I sent a simple patch dropping the call to drm_crtc_cleanup():
https://lore.kernel.org/dri-devel/20241031183835.3633-1-jose.exposito89@gmail.com/T/#u

About this patch, LGTM.

Jose

> Thanks,
> Louis Chauvet
> 
> > The rest looks fine to me.
> >
> > Best Regards,
> > - Maíra
> > 
> > >   	return ret;
> > > diff --git a/drivers/gpu/drm/vkms/vkms_plane.c b/drivers/gpu/drm/vkms/vkms_plane.c
> > > index e5c625ab8e3e..ad137c9a75f5 100644
> > > --- a/drivers/gpu/drm/vkms/vkms_plane.c
> > > +++ b/drivers/gpu/drm/vkms/vkms_plane.c
> > > @@ -198,12 +198,12 @@ static const struct drm_plane_helper_funcs vkms_plane_helper_funcs = {
> > >   };
> > >   struct vkms_plane *vkms_plane_init(struct vkms_device *vkmsdev,
> > > -				   enum drm_plane_type type, int index)
> > > +				   enum drm_plane_type type)
> > >   {
> > >   	struct drm_device *dev = &vkmsdev->drm;
> > >   	struct vkms_plane *plane;
> > > -	plane = drmm_universal_plane_alloc(dev, struct vkms_plane, base, 1 << index,
> > > +	plane = drmm_universal_plane_alloc(dev, struct vkms_plane, base, 0,
> > >   					   &vkms_plane_funcs,
> > >   					   vkms_formats, ARRAY_SIZE(vkms_formats),
> > >   					   NULL, type, NULL);
> > > 
> > > ---
> > > base-commit: 33c255312660653cf54f8019896b5dca28e3c580
> > > change-id: 20240906-vkms-remove-index-3a6e04c38e02
> > > 
> > > Best regards,