Re: [PATCH RESEND v2 15/32] drm/vkms: Introduce configfs for plane color range

Luca Ceresoli
2025-12-18T18:00:56Z

On Wed Oct 29, 2025 at 3:36 PM CET, Louis Chauvet wrote:
> To allows the userspace to test many hardware configuration, introduce a
> new interface to configure the available color ranges per planes. VKMS
> supports multiple color ranges, so the userspace can choose any
> combination.
>
> The supported color ranges are configured by writing a color range bitmask
> to the file `supported_color_ranges` and the default color range is
> chosen by writing a color encoding bitmask to `default_color_range`.
>
> Signed-off-by: Louis Chauvet <louis.chauvet@bootlin.com>

> diff --git a/drivers/gpu/drm/vkms/vkms_configfs.c b/drivers/gpu/drm/vkms/vkms_configfs.c
> index ee2e8d141f9e..3f658dd41272 100644
> --- a/drivers/gpu/drm/vkms/vkms_configfs.c
> +++ b/drivers/gpu/drm/vkms/vkms_configfs.c
> @@ -439,6 +439,91 @@ static ssize_t plane_default_rotation_store(struct config_item *item,
> return count;
> }
>
> +static ssize_t plane_supported_color_ranges_show(struct config_item *item, char *page)
> +{
> + struct vkms_configfs_plane *plane;
> + unsigned int supported_color_range;
supported_color_ranges

> +
> + plane = plane_item_to_vkms_configfs_plane(item);

As for previous patches, set this on declaration for consistency (same below).

> +static ssize_t plane_supported_color_ranges_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_LIMITED_RANGE) |
> + BIT(DRM_COLOR_YCBCR_FULL_RANGE)))
> + return -EINVAL;
> + /* Should at least provide one color range */
> + if ((val & (BIT(DRM_COLOR_YCBCR_LIMITED_RANGE) |
> + BIT(DRM_COLOR_YCBCR_FULL_RANGE))) == 0)
> + return -EINVAL;
> +
> + scoped_guard(mutex, &plane->dev->lock) {
> + /* Ensures that the default rotation is included in supported rotation */

Oh no, that comment again! :-)

> +static ssize_t plane_default_color_range_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_LIMITED_RANGE) |
> + BIT(DRM_COLOR_YCBCR_FULL_RANGE)))
> + return -EINVAL;
> + /* Should at least provide one color range */
> + if ((val & (BIT(DRM_COLOR_YCBCR_LIMITED_RANGE) |
> + BIT(DRM_COLOR_YCBCR_FULL_RANGE))) == 0)
> + return -EINVAL;

As in patch 12, replace this with is_power_of_2() to check that exactly one
bit is set.

Luca

--
Luca Ceresoli, Bootlin
Embedded Linux and Kernel engineering