> -----Original Message-----
> From: Ville Syrjälä <ville.syrj...@linux.intel.com>
> Sent: Tuesday, January 28, 2025 12:44 AM
> To: Borah, Chaitanya Kumar <chaitanya.kumar.bo...@intel.com>
> Cc: Murthy, Arun R <arun.r.mur...@intel.com>; dri-
> de...@lists.freedesktop.org; intel-gfx@lists.freedesktop.org; intel-
> x...@lists.freedesktop.org
> Subject: Re: [PATCH v3 2/5] drm/plane: Expose function to create
> format/modifier blob
>
> On Mon, Jan 27, 2025 at 07:25:31AM +0000, Borah, Chaitanya Kumar wrote:
> > Hello Ville,
> >
> > > -----Original Message-----
> > > From: Intel-xe <intel-xe-boun...@lists.freedesktop.org> On Behalf Of
> > > Murthy, Arun R
> > > Sent: Saturday, January 25, 2025 12:25 PM
> > > To: Ville Syrjälä <ville.syrj...@linux.intel.com>
> > > Cc: dri-de...@lists.freedesktop.org;
> > > intel-gfx@lists.freedesktop.org; intel- x...@lists.freedesktop.org
> > > Subject: RE: [PATCH v3 2/5] drm/plane: Expose function to create
> > > format/modifier blob
> > >
> > > > On Thu, Jan 23, 2025 at 07:47:14AM +0000, Murthy, Arun R wrote:
> > > > > > > On Wed, Jan 08, 2025 at 11:09:00AM +0530, Arun R Murthy wrote:
> > > > > > > > Expose drm plane function to create formats/modifiers blob.
> > > > > > > > This function can be used to expose list of supported
> > > > > > > > formats/modifiers for sync/async flips.
> > > > > > > >
> > > > > > > > Signed-off-by: Arun R Murthy <arun.r.mur...@intel.com>
> > > > > > > > ---
> > > > > > > > drivers/gpu/drm/drm_plane.c | 44
> > > > > > > > +++++++++++++++++++++++++++++-------
> > > > > > > --------
> > > > > > > > include/drm/drm_plane.h | 4 ++++
> > > > > > > > 2 files changed, 33 insertions(+), 15 deletions(-)
> > > > > > > >
> > > > > > > > diff --git a/drivers/gpu/drm/drm_plane.c
> > > > > > > > b/drivers/gpu/drm/drm_plane.c index
> > > > > > > >
> > > > > > >
> > > > > >
> > > >
> > >
> 416818e54ccffcf3d3aada2723e96ce8ccf1dd97..4f35eec2b7770fcc90c3e07a90
> > > > > > 6
> > > > > > > 8
> > > > > > > > b31c0563a4c0 100644
> > > > > > > > --- a/drivers/gpu/drm/drm_plane.c
> > > > > > > > +++ b/drivers/gpu/drm/drm_plane.c
> > > > > > > > @@ -191,7 +191,10 @@ modifiers_ptr(struct
> > > > > > > > drm_format_modifier_blob
> > > > > > > *blob)
> > > > > > > > return (struct drm_format_modifier *)(((char *)blob) +
> > > > > > > > blob->modifiers_offset); }
> > > > > > > >
> > > > > > > > -static int create_in_format_blob(struct drm_device *dev,
> > > > > > > > struct drm_plane *plane)
> > > > > > > > +int drm_plane_create_format_blob(struct drm_device *dev,
> > > > > > > > + struct drm_plane *plane, u64
> > > > *modifiers,
> > > > > > > > + unsigned int modifier_count,
> > > > > > > > u32
> > > > *formats,
> > > > > > > > + unsigned int format_count, bool
> > > > is_async)
> > > > > > > > {
> > > > > > > > const struct drm_mode_config *config =
> > > > > > > > &dev->mode_config;
> > > > > > > > struct drm_property_blob *blob; @@ -200,14 +203,14 @@
> > > static
> > > > > > > > int create_in_format_blob(struct drm_device
> > > > > > > *dev, struct drm_plane *plane
> > > > > > > > struct drm_format_modifier_blob *blob_data;
> > > > > > > > unsigned int i, j;
> > > > > > > >
> > > > > > > > - formats_size = sizeof(__u32) * plane->format_count;
> > > > > > > > + formats_size = sizeof(__u32) * format_count;
> > > > > > > > if (WARN_ON(!formats_size)) {
> > > > > > > > /* 0 formats are never expected */
> > > > > > > > return 0;
> > > > > > > > }
> > > > > > > >
> > > > > > > > modifiers_size =
> > > > > > > > - sizeof(struct drm_format_modifier) * plane-
> > > >modifier_count;
> > > > > > > > + sizeof(struct drm_format_modifier) *
> > > > > > > > modifier_count;
> > > > > > > >
> > > > > > > > blob_size = sizeof(struct drm_format_modifier_blob);
> > > > > > > > /* Modifiers offset is a pointer to a struct with a 64
> > > > > > > > bit field so it @@ -223,37 +226,45 @@ static int
> > > > > > > > create_in_format_blob(struct drm_device *dev, struct
> > > > > > > > drm_plane *plane
> > > > > > > >
> > > > > > > > blob_data = blob->data;
> > > > > > > > blob_data->version = FORMAT_BLOB_CURRENT;
> > > > > > > > - blob_data->count_formats = plane->format_count;
> > > > > > > > + blob_data->count_formats = format_count;
> > > > > > > > blob_data->formats_offset = sizeof(struct
> > > drm_format_modifier_blob);
> > > > > > > > - blob_data->count_modifiers = plane->modifier_count;
> > > > > > > > + blob_data->count_modifiers = modifier_count;
> > > > > > > >
> > > > > > > > blob_data->modifiers_offset =
> > > > > > > > ALIGN(blob_data->formats_offset + formats_size,
> > > > > > > > 8);
> > > > > > > >
> > > > > > > > - memcpy(formats_ptr(blob_data), plane->format_types,
> > > formats_size);
> > > > > > > > + memcpy(formats_ptr(blob_data), formats, formats_size);
> > > > > > > >
> > > > > > > > mod = modifiers_ptr(blob_data);
> > > > > > > > - for (i = 0; i < plane->modifier_count; i++) {
> > > > > > > > - for (j = 0; j < plane->format_count; j++) {
> > > > > > > > - if (!plane->funcs->format_mod_supported
> > > > > > > > ||
> > > > > > > > + for (i = 0; i < modifier_count; i++) {
> > > > > > > > + for (j = 0; j < format_count; j++) {
> > > > > > > > + if (is_async ||
> > > > > > > > + !plane->funcs->format_mod_supported
> > > > > > > > ||
> > > > > > > > plane->funcs-
> > > >format_mod_supported(plane,
> > > > > > > > -
> > > > > > > > plane-
> > > > > > > >format_types[j],
> > > > > > > > -
> > > > > > > > plane-
> > > > > > > >modifiers[i])) {
> > > > > > > > +
> > > > > > > > formats[j],
> > > > > > > > +
> > > > modifiers[i])) {
> > > > > > > > mod->formats |= 1ULL << j;
> > > > > > > > }
> > > > > > > > }
> > > > > > > >
> > > > > > > > - mod->modifier = plane->modifiers[i];
> > > > > > > > + mod->modifier = modifiers[i];
> > > > > > > > mod->offset = 0;
> > > > > > > > mod->pad = 0;
> > > > > > > > mod++;
> > > > > > > > }
> > > > > > > >
> > > > > > > > - drm_object_attach_property(&plane->base, config-
> > > > > > > >modifiers_property,
> > > > > > > > - blob->base.id);
> > > > > > > > + if (is_async)
> > > > > > > > + drm_object_attach_property(&plane->base,
> > > > > > > > + config-
> > > > >async_modifiers_property,
> > > > > > > > + blob->base.id);
> > > > > > > > + else
> > > > > > > > + drm_object_attach_property(&plane->base,
> > > > > > > > +
> > > > > > > > config->modifiers_property,
> > > > > > > > + blob->base.id);
> > > > > > >
> > > > > > > IMO the function should only create the blob. Leave it to
> > > > > > > the caller to attach
> > > > > > it.
> > > > > > >
> > > > > > Prior to this change for sync formats/modifiers the property
> > > > > > attach was also done in the same function. So retained it as it.
> > > > > >
> > > > > > > The 'is_async' parameter could also be replaced with with a
> > > > > > > function pointer to the appropriate format_mod_supported()
> > > > > > > function. That makes the implementation entirely generic.
> > > > > > >
> > > > > > If the list of formats/modifiers for sync and async is passed
> > > > > > to this function, then based on the list the corresponding
> > > > > > function pointer can
> > > > be called.
> > > > > > This was done in the earlier patchset.
> > > > > >
> > > > > > > >
> > > > > > > > return 0;
> > > > > > > > }
> > > > > > > > +EXPORT_SYMBOL(drm_plane_create_format_blob);
> > > > > > > >
> > > > > > > > /**
> > > > > > > > * DOC: hotspot properties @@ -476,7 +487,10 @@ static
> > > > > > > > int __drm_universal_plane_init(struct
> > > > > > > drm_device *dev,
> > > > > > > > }
> > > > > > > >
> > > > > > > > if (format_modifier_count)
> > > > > > > > - create_in_format_blob(dev, plane);
> > > > > > > > + drm_plane_create_format_blob(dev, plane, plane-
> > > > >modifiers,
> > > > > > > > +
> > > > > > > > format_modifier_count,
> > > > > > > > +
> > > > > > > > plane->format_types,
> > > > > > > format_count,
> > > > > > > > + false);
> > > > > > > >
> > > > > > > > return 0;
> > > > > > > > }
> > > > > > > > diff --git a/include/drm/drm_plane.h
> > > > > > > > b/include/drm/drm_plane.h index
> > > > > > > >
> > > > > > >
> > > > > >
> > > >
> > >
> e8749e6fc3bc0acfc73bbd8401f85c3126e86759..eb84830fbb723e39436bfbadf
> > > > > > > 369
> > > > > > > > 894a5657cd45 100644
> > > > > > > > --- a/include/drm/drm_plane.h
> > > > > > > > +++ b/include/drm/drm_plane.h
> > > > > > > > @@ -1008,5 +1008,9 @@ int
> > > > > > > > drm_plane_create_scaling_filter_property(struct drm_plane
> > > > > > > > *plane, int
> > > > > > > drm_plane_add_size_hints_property(struct drm_plane *plane,
> > > > > > > > const struct
> > > > > > > > drm_plane_size_hint
> > > *hints,
> > > > > > > > int num_hints);
> > > > > > > > +int drm_plane_create_format_blob(struct drm_device *dev,
> > > > > > > > + struct drm_plane *plane, u64
> > > > *modifiers,
> > > > > > > > + unsigned int modifier_count,
> > > > > > > > u32
> > > > *formats,
> > > > > > > > + unsigned int format_count, bool
> > > > is_async);
> > > > > > >
> > > > > > > I don't think this needs to be exposed to anyone.
> > > > > > > __drm_universal_plane_init() should just populate both the
> > > > > > > normal blob, and and the async blob (iff
> > > > > > > .format_mod_supported_async() is provided).
> > > > > > >
> > > > > > Ok!
> > > > > >
> > > > > For __drm_universal_plane_init() to have both the sync/async
> > > > format/modifiers list we will have to add new elements to struct
> > > > drm_plane to hold the async formats/modifiers.
> > > >
> > > > No, you can just use the already existing format/modifier lists.
> > > > .format_mod_supported_async() will filter out what's not wanted.
> > > >
> > > Agree, to populate the struct drm_format_modifier
> > > .format_mod_supported_async along with the existing formats/modifier
> > > list should be sufficient.
> > > In case of async for the struct drm_format_modifier_blob the
> > > elements format_offset includes the list of formats supported by
> > > async only. For this we will need to have the static list. So can
> > > passing this list be done by adding new elements in drm_plane specifically
> for async.
> >
> > Just to add to Arun's point. We had this discussion on thread [1].
> >
> > If we populate struct drm_format_modifier_blob for async using just
> > the existing format/modifier lists in struct drm_plane, We will be
> > mis-representing the following members of the structure to the user
> > space
> >
> > struct drm_format_modifier_blob {
> > /* Number of fourcc formats supported */
> > __u32 count_formats;
> >
> > /* Number of drm_format_modifiers */
> > __u32 count_modifiers;
> > };
>
> Nothing is misrepresentd. Those things just tell you what the bits in the
> bimask mean.
>
At the very least, it makes the comments inaccurate. But perhaps something we
can live with.
> >
> > However, as you correctly point out, it should still work because of the
> format-modifier bit mask.
> > But it leaves the overall blob unnecessarily bloated (for example, with
> unnecessary entries in the format list).
> >
> > We could however change the function in such a way that the loop
> >
> > for (i = 0; i < modifier_count; i++) {
> > for (j = 0; j < format_count; j++)
> >
> > runs before filling up these members.
> >
> > I am not sure how much juggling that would take but it could be a solution.
> >
> > Anything you would suggest?
>
> You're complicating things needlessly. The slightly bloated blob should make
> no practical difference anywhere.
>
I agree, if bloated blob is not a concern then we can re-use the existing
struct drm_plane members and keep the function more or less the same.
Regards
Chaitanya
> --
> Ville Syrjälä
> Intel
