Re: [PATCH v7 4/7] drm/edid: parse DSC DPP passthru support flag for mode VII timings
From: Jani Nikula
Date: Thu Dec 04 2025 - 07:11:12 EST
On Tue, 02 Dec 2025, Yaroslav Bolyukin <iam@xxxxxxx> wrote:
> For timings v7 block revision >=1, revision field also contains a bit
> that indicates that the mode timings should only be used with fixed bits
> per pixel value specified in vesa vendor-specific block.
>
> Signed-off-by: Yaroslav Bolyukin <iam@xxxxxxx>
On the EDID/DisplayID parts,
Reviewed-by: Jani Nikula <jani.nikula@xxxxxxxxx>
but I'd like to get ack from e.g. Ville about the
dsc_passthrough_timings_support member in struct drm_display_mode.
> ---
> drivers/gpu/drm/drm_displayid_internal.h | 2 ++
> drivers/gpu/drm/drm_edid.c | 12 ++++++++----
> include/drm/drm_modes.h | 10 ++++++++++
> 3 files changed, 20 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/gpu/drm/drm_displayid_internal.h b/drivers/gpu/drm/drm_displayid_internal.h
> index 72f107ae832f..724174b429f2 100644
> --- a/drivers/gpu/drm/drm_displayid_internal.h
> +++ b/drivers/gpu/drm/drm_displayid_internal.h
> @@ -97,6 +97,7 @@ struct displayid_header {
> u8 ext_count;
> } __packed;
>
> +#define DISPLAYID_BLOCK_REV GENMASK(2, 0)
> struct displayid_block {
> u8 tag;
> u8 rev;
> @@ -125,6 +126,7 @@ struct displayid_detailed_timings_1 {
> __le16 vsw;
> } __packed;
>
> +#define DISPLAYID_BLOCK_PASSTHROUGH_TIMINGS_SUPPORT BIT(3)
> struct displayid_detailed_timing_block {
> struct displayid_block base;
> struct displayid_detailed_timings_1 timings[];
> diff --git a/drivers/gpu/drm/drm_edid.c b/drivers/gpu/drm/drm_edid.c
> index 380a9dda275f..b28ff4bafb1d 100644
> --- a/drivers/gpu/drm/drm_edid.c
> +++ b/drivers/gpu/drm/drm_edid.c
> @@ -6794,8 +6794,8 @@ static void update_display_info(struct drm_connector *connector,
> }
>
> static struct drm_display_mode *drm_mode_displayid_detailed(struct drm_device *dev,
> - const struct displayid_detailed_timings_1 *timings,
> - bool type_7)
> + const struct displayid_block *block,
> + const struct displayid_detailed_timings_1 *timings)
> {
> struct drm_display_mode *mode;
> unsigned int pixel_clock = (timings->pixel_clock[0] |
> @@ -6811,11 +6811,16 @@ static struct drm_display_mode *drm_mode_displayid_detailed(struct drm_device *d
> unsigned int vsync_width = le16_to_cpu(timings->vsw) + 1;
> bool hsync_positive = le16_to_cpu(timings->hsync) & (1 << 15);
> bool vsync_positive = le16_to_cpu(timings->vsync) & (1 << 15);
> + bool type_7 = block->tag == DATA_BLOCK_2_TYPE_7_DETAILED_TIMING;
>
> mode = drm_mode_create(dev);
> if (!mode)
> return NULL;
>
> + if (type_7 && FIELD_GET(DISPLAYID_BLOCK_REV, block->rev) >= 1)
> + mode->dsc_passthrough_timings_support =
> + block->rev & DISPLAYID_BLOCK_PASSTHROUGH_TIMINGS_SUPPORT;
> +
> /* resolution is kHz for type VII, and 10 kHz for type I */
> mode->clock = type_7 ? pixel_clock : pixel_clock * 10;
> mode->hdisplay = hactive;
> @@ -6848,7 +6853,6 @@ static int add_displayid_detailed_1_modes(struct drm_connector *connector,
> int num_timings;
> struct drm_display_mode *newmode;
> int num_modes = 0;
> - bool type_7 = block->tag == DATA_BLOCK_2_TYPE_7_DETAILED_TIMING;
> /* blocks must be multiple of 20 bytes length */
> if (block->num_bytes % 20)
> return 0;
> @@ -6857,7 +6861,7 @@ static int add_displayid_detailed_1_modes(struct drm_connector *connector,
> for (i = 0; i < num_timings; i++) {
> struct displayid_detailed_timings_1 *timings = &det->timings[i];
>
> - newmode = drm_mode_displayid_detailed(connector->dev, timings, type_7);
> + newmode = drm_mode_displayid_detailed(connector->dev, block, timings);
> if (!newmode)
> continue;
>
> diff --git a/include/drm/drm_modes.h b/include/drm/drm_modes.h
> index b9bb92e4b029..312e5c03af9a 100644
> --- a/include/drm/drm_modes.h
> +++ b/include/drm/drm_modes.h
> @@ -417,6 +417,16 @@ struct drm_display_mode {
> */
> enum hdmi_picture_aspect picture_aspect_ratio;
>
> + /**
> + * @dsc_passthrough_timing_support:
> + *
> + * Indicates whether this mode timing descriptor is supported
> + * with specific target DSC bits per pixel only.
> + *
> + * VESA vendor-specific data block shall exist with the relevant
> + * DSC bits per pixel declaration when this flag is set to true.
> + */
> + bool dsc_passthrough_timings_support;
> };
>
> /**
--
Jani Nikula, Intel