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Message-ID: <aPuYV5D_QktyNSmM@fedora>
Date: Fri, 24 Oct 2025 17:16:39 +0200
From: José Expósito <jose.exposito89@...il.com>
To: Louis Chauvet <louis.chauvet@...tlin.com>
Cc: Haneen Mohammed <hamohammed.sa@...il.com>,
Simona Vetter <simona@...ll.ch>,
Melissa Wen <melissa.srw@...il.com>,
Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
Maxime Ripard <mripard@...nel.org>,
Thomas Zimmermann <tzimmermann@...e.de>,
David Airlie <airlied@...il.com>, Jonathan Corbet <corbet@....net>,
victoria@...tem76.com, sebastian.wick@...hat.com,
thomas.petazzoni@...tlin.com, dri-devel@...ts.freedesktop.org,
linux-kernel@...r.kernel.org, linux-doc@...r.kernel.org
Subject: Re: [PATCH 06/22] drm/vkms: Introduce configfs for plane color
encoding
On Sat, Oct 18, 2025 at 04:01:06AM +0200, Louis Chauvet wrote:
> To allows the userspace to test many hardware configuration, introduce a
> new interface to configure the available color encoding per planes. VKMS
> supports multiple color encoding, so the userspace can choose any
> combination.
>
> The supported color encoding are configured by writing a color encoding
> bitmask to the file `supported_color_encoding` and the default color
> encoding is chosen by writing a color encoding bitmask to
> `default_color_encoding`.
>
> Signed-off-by: Louis Chauvet <louis.chauvet@...tlin.com>
> ---
> Documentation/gpu/vkms.rst | 7 ++-
> drivers/gpu/drm/vkms/vkms_configfs.c | 102 +++++++++++++++++++++++++++++++++++
> 2 files changed, 108 insertions(+), 1 deletion(-)
>
> diff --git a/Documentation/gpu/vkms.rst b/Documentation/gpu/vkms.rst
> index a432968cc711..4ff75b53a386 100644
> --- a/Documentation/gpu/vkms.rst
> +++ b/Documentation/gpu/vkms.rst
> @@ -87,7 +87,7 @@ Start by creating one or more planes::
>
> sudo mkdir /config/vkms/my-vkms/planes/plane0
>
> -Planes have 3 configurable attribute:
> +Planes have 5 configurable attribute:
>
> - type: Plane type: 0 overlay, 1 primary, 2 cursor (same values as those
> exposed by the "type" property of a plane)
> @@ -96,6 +96,11 @@ Planes have 3 configurable attribute:
> (same values as those exposed by the "rotation" property of a plane)
> - default_rotation: Default rotation presented to the userspace, same values as
> possible_rotations.
> +- supported_color_encoding: Available encoding for a plane, as a bitmask:
> + 0x01 YCBCR_BT601, 0x02: YCBCR_BT709, 0x04 YCBCR_BT2020 (same values as those exposed
> + by the COLOR_ENCODING property of a plane)
> +- default_color_encoding: Default color encoding presented to the userspace, same
> + values as supported_color_encoding
>
> Continue by creating one or more CRTCs::
>
> diff --git a/drivers/gpu/drm/vkms/vkms_configfs.c b/drivers/gpu/drm/vkms/vkms_configfs.c
> index 450e45e66a45..a4e0e054cf2d 100644
> --- a/drivers/gpu/drm/vkms/vkms_configfs.c
> +++ b/drivers/gpu/drm/vkms/vkms_configfs.c
> @@ -412,14 +412,116 @@ static ssize_t plane_default_rotation_store(struct config_item *item,
> return count;
> }
>
> +static ssize_t plane_supported_color_encoding_show(struct config_item *item, char *page)
> +{
> + struct vkms_configfs_plane *plane;
> + unsigned int supported_color_encoding;
> +
> + plane = plane_item_to_vkms_configfs_plane(item);
> +
> + scoped_guard(mutex, &plane->dev->lock) {
> + supported_color_encoding = vkms_config_plane_get_supported_color_encoding(plane->config);
> + }
> +
> + return sprintf(page, "%u", supported_color_encoding);
> +}
> +
> +static ssize_t plane_supported_color_encoding_store(struct config_item *item,
> + const char *page, size_t count)
> +{
> + struct vkms_configfs_plane *plane = plane_item_to_vkms_configfs_plane(item);
> + int ret, val = 0;
> +
> + ret = kstrtouint(page, 10, &val);
> + if (ret)
> + return ret;
> +
> + /* Should be a supported value */
> + if (val & ~(BIT(DRM_COLOR_YCBCR_BT601) |
> + BIT(DRM_COLOR_YCBCR_BT709) |
> + BIT(DRM_COLOR_YCBCR_BT2020)))
> + return -EINVAL;
> + /* Should at least provide one color range */
> + if ((val & (BIT(DRM_COLOR_YCBCR_BT601) |
> + BIT(DRM_COLOR_YCBCR_BT709) |
> + BIT(DRM_COLOR_YCBCR_BT2020))) == 0)
> + return -EINVAL;
> +
> + scoped_guard(mutex, &plane->dev->lock) {
> + /* Ensures that the default rotation is included in supported rotation */
> + if (plane->dev->enabled ||
> + (val & vkms_config_plane_get_default_color_encoding(plane->config)) !=
> + vkms_config_plane_get_default_color_encoding(plane->config))
> + return -EINVAL;
I think that the same problem that I mention having to configure
plane rotation in 2 steps applies for color encoding.
> + vkms_config_plane_set_supported_color_encoding(plane->config, val);
> + }
> +
> + return count;
> +}
> +
> +/* Plane default_color_encoding : vkms/<device>/planes/<plane>/default_color_encoding */
> +
> +static ssize_t plane_default_color_encoding_show(struct config_item *item, char *page)
> +{
> + struct vkms_configfs_plane *plane;
> + unsigned int default_color_encoding;
> +
> + plane = plane_item_to_vkms_configfs_plane(item);
> +
> + scoped_guard(mutex, &plane->dev->lock) {
> + default_color_encoding = vkms_config_plane_get_default_color_encoding(plane->config);
> + }
> +
> + return sprintf(page, "%u", default_color_encoding);
> +}
> +
> +static ssize_t plane_default_color_encoding_store(struct config_item *item,
> + const char *page, size_t count)
> +{
> + struct vkms_configfs_plane *plane = plane_item_to_vkms_configfs_plane(item);
> + int ret, val = 0;
> +
> + ret = kstrtouint(page, 10, &val);
> + if (ret)
> + return ret;
> +
> + /* Should be a supported value */
> + if (val & ~(BIT(DRM_COLOR_YCBCR_BT601) |
> + BIT(DRM_COLOR_YCBCR_BT709) |
> + BIT(DRM_COLOR_YCBCR_BT2020)))
> + return -EINVAL;
> + /* Should at least provide one color range */
> + if ((val & (BIT(DRM_COLOR_YCBCR_BT601) |
> + BIT(DRM_COLOR_YCBCR_BT709) |
> + BIT(DRM_COLOR_YCBCR_BT2020))) == 0)
> + return -EINVAL;
> +
> + scoped_guard(mutex, &plane->dev->lock) {
> + /* Ensures that the default rotation is included in supported rotation */
> + if (plane->dev->enabled ||
> + (val & vkms_config_plane_get_supported_color_encoding(plane->config)) !=
> + val)
> + return -EINVAL;
> +
> + vkms_config_plane_set_default_color_encoding(plane->config, val);
As I mentioned in the previous patch, I think that default color encoding
is sometimes a bitmask and sometimes the actual color?
> + }
> +
> + return count;
> +}
> +
> CONFIGFS_ATTR(plane_, type);
> CONFIGFS_ATTR(plane_, supported_rotations);
> CONFIGFS_ATTR(plane_, default_rotation);
> +CONFIGFS_ATTR(plane_, supported_color_encoding);
> +CONFIGFS_ATTR(plane_, default_color_encoding);
>
> static struct configfs_attribute *plane_item_attrs[] = {
> &plane_attr_type,
> &plane_attr_supported_rotations,
> &plane_attr_default_rotation,
> + &plane_attr_supported_color_encoding,
> + &plane_attr_default_color_encoding,
> NULL,
> };
>
>
> --
> 2.51.0
>
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