[PATCH v9 00/19] Add new general DRM property "color format"
Nicolas Frattaroli
nicolas.frattaroli at collabora.com
Fri Feb 27 11:20:05 PST 2026
Hello,
this is a follow-up to
https://lore.kernel.org/all/20250911130739.4936-1-marius.vlad@collabora.com/
which in of itself is a follow-up to
https://lore.kernel.org/dri-devel/20240115160554.720247-1-andri@yngvason.is/ where
a new DRM connector property has been added allowing users to
force a particular color format.
That in turn was actually also a follow-up from Werner Sembach's posted at
https://lore.kernel.org/dri-devel/20210630151018.330354-1-wse@tuxedocomputers.com/
As the number of cooks have reached critical mass, I'm hoping I'll be
the last person to touch this particular series.
We have an implementation in Weston at
https://gitlab.freedesktop.org/wayland/weston/-/merge_requests/1825 that
adds support for this property. This patch series has been tested
against that MR on i915 (HDMI, DP), amdgpu (HDMI, DP) and on rockchip
(HDMI).
You can also manually test this with modetest like so, but beware that
this is a non-atomic invocation, so testing YUV420 like this will result
in weird outcomes if only some of the modes support YUV420:
$ modetest -s 115:1920x1080-60 at NV12 -w 115:'color format':4
where 115 is the connector ID and '4' is the enum value for a particular
color format.
General notes on the approach taken by me: instead of silently switching
to a different format than was explicitly requested, or even worse,
outputting something to the sink the sink doesn't support, bubble up an
error to userspace instead. "color format" is a "I want this" type
property, not a "force this" type property, i.e. the kernel will respect
the limits imposed by the hardware.
Things I've tested:
- HDMI (YCbCr 4:4:4 + YCbCr 4:2:2 (8-bit) + RGB + Auto) on RK3588
- HDMI (YCbCr 4:4:4 + YCbCr 4:2:2 (8-bit) + RGB + Auto) on RK3576
- HDMI + DP (YCbCr 4:4:4, YCbCr 4:2:0, RGB, Auto) on Intel N97 (i915)
DP-MST is untested, and no longer trivially equivalent.
- HDMI (YCbCr 4:4:4, YCbCr 4:2:2, YCbCr 4:2:0, RGB, Auto) + DP (YCbCr
4:4:4, RGB, Auto) on an AMD Radeon RX 550 (amdgpu). DP-MST is
untested.
Signed-off-by: Nicolas Frattaroli <nicolas.frattaroli at collabora.com>
---
Changes in v9:
- Document what the "AUTO" behaviour is in the color format enum (thanks
to Maxime)
- drm/bridge: dw-hdmi-qp: Fix a rebase oopsie that reintroduced some
functions that were dropped. (thanks to Cristian)
- drm/bridge: Shuffle "1:1" in the bridge fmt selection docs to earlier
in the sentence. (thanks to Randy Dunlap)
- i915: Check chosen output format against requested format for dp-mst
- All color format driver implementations: rebase and rework on top of
Maxime's series
- As part of this rework, rename drm_color_format_enum to
drm_connector_color_format
- drm kunit tests: rework for the new enums. Changes were trivial, so
trailers were kept
- Link to v8: https://lore.kernel.org/r/20260216-color-format-v8-0-5722ce175dd5@collabora.com
Changes in v8:
- Drop "drm/rockchip: vop2: Fix YUV444 output", as the original problem
could not be reproduced anymore, and the justification did not make
sense.
- Remove the 12-bit format from "drm/rockchip: vop2: Recognise 10/12-bit
YUV422 as YUV formats".
- Refactor to keep the original DRM_COLOR_FORMAT bitshifted defines
as-is, but introduce a new drm_color_format_enum enum.
- Adjust conversion functions for the newly refactored enum, ensuring
they only return valid enum values, and only convert in directions
that open up no error value cans of worms.
- Rework the property uapi code for the newly refactored enum, since
it no longer needs to do any bitshifting or ffs().
- Rework all the device drivers for the new enum.
- Rework all the tests for the refactored enum.
- Rework the hdmi state helper for the new enum, and also make it more
explicit about the auto behaviour by not relying on a conversion
function to map AUTO to RGB, but do this in the framework itself.
- rockchip dw_hdmi_qp: Fix the GRF value to check for color >= 0 instead
of color > 0, as the latter broke switching back to RGB.
- Rebase onto a recent drm-tip. This necessitated blindly reworking some
of the i915 dp-mst code.
- Drop the __maybe_unused edid test patch, as I could no longer
reproduce the build warnings I added it for. I blame ghosts.
- drm_bridge tests: remove "destroyed" member from struct
drm_bridge_chain_priv and all associated code, as it was not used in
any test.
- Link to v7: https://lore.kernel.org/r/20260121-color-format-v7-0-ef790dae780c@collabora.com
Changes in v7:
- Fix drm_bridge kunit test build failure caused by rebasing across an
API change.
- Make compilers shut up about unused EDID definitions in the test
suites.
- Empty line checkpatch fixes that b4 prep --check didn't catch.
- Link to v6: https://lore.kernel.org/r/20260121-color-format-v6-0-7b81a771cd0b@collabora.com
Changes in v6:
- Checkpatch fixes
- Add drm_bridge.c kerneldoc fix patch to b4 deps so the kernel docs
required for every contribution to the subsystem can be built
- dw-hdmi-qp core has gained the atomic_get_output_bus_fmts bridge func,
which allows it to participate in the drm_bridge chain recursive format
selection code properly.
- The Rockchip dw-hdmi-qp integration now no longer reimplements the
color format logic (improperly), but reads the bus format of the first
bridge as set by the recursive bridge format selection. If the input
format is FIXED, it'll use the output format. Otherwise, the input
format is used.
- In the synopsys drivers, YUV422 uses the same bus format as the non-qp
hdmi encoder driver. Probably correcter this way. The Rockchip vop2
is_yuv function has been extended to recognise this format as well.
- KUnit tests for drm_bridge chains are now included, which exercise the
chain's recursive bus format selection.
- On HDMI connectors, the drm_bridge bus format selection will try to target
the color format that the HDMI layer came up with. This means the AUTO
logic is not duplicated for HDMI connectors.
- The enum conversion function commit gained a function for converting
from hdmi_colorspace to drm_color_format, and its author changed as no
original code remains anyway. Marius is still included as a
Co-developer.
- Some tests for the HDMI state helper's mode_valid have been written.
They are incomplete as we lack a test EDID for a 420-also mode that
would violate the clock constraints on RGB. I hacked one together with
a hex editor, but it reports a too high of a clock rate, and there's
no EDID editor I could find which supports these extension blocks.
- The color_format KUnit tests have been more heavily parameterised, the
auto case absorbed into other tests, and the comments around them
rewritten.
- Add a few paragraphs of documentation that explain the bridge format
selection, and how to make use of it in a display driver.
- Link to v5: https://lore.kernel.org/r/20251128-color-format-v5-0-63e82f1db1e1@collabora.com
Changes in v5:
- Rebase onto drm-tip
- Drop DRM_MODE_COLOR_FORMAT_* as an enum
- Unify DRM_COLOR_FORMAT_NONE and DRM_COLOR_FORMAT_AUTO, with AUTO being
0. This makes conversion and general logic much easier.
- Adjust the drm_color_format enum to not needlessly renumber the
existing defines, as it doesn't need to correspond to how HDMI numbers
them.
- Make the DRM-to-HDMI conversion function static inline __pure, because
the assembly it generates is tiny, and the function is pure.
- Don't accept nothing as the list of supported color formats for
registration of the property.
- Drop the per-connector variants of the color format registration
function, as it's not needed.
- drm_hdmi_state_helper: Fix mode_valid rejecting 420-only modes.
- drm_hdmi_state_helper: Only fall back to YUV420 with
DRM_COLOR_FORMAT_AUTO.
- drm_hdmi_state_helper: Remove redundant AUTO->RGB condition, as the
conversion already does this.
- Add KUnit tests for hdmi_compute_config.
- drm/bridge: Refactor bus_format_is_color_fmt and add a few more YUV422
formats.
- Register the color format property in drmm_connector_hdmi_init based
on the supported HDMI formats passed to it. This means rockchip
dw_hdmi_qp no longer needs to register it.
- amdgpu: Simplify YUV420 logic
- amdgpu: Don't try to pick YUV444 on YUV420-only modes
- i915: Try to make behaviour more or less the same as that of the drm
hdmi state helper.
- rockchip dw_hdmi_qp: Set supported HDMI formats
- rockchip dw_hdmi_qp: Set the right VO GRF values depending on color
format.
- rockchip dw_hdmi_qp: Act on the color format property in this driver,
rather than in VOP2, by setting the bus_format appropriately.
- rockchip VOP2: Can the BCSH-based implementation. BCSH isn't available
on all video ports of the hardware, and the code was extremely
suspect. Instead, plug into the existing YUV-to-RGB/RGB-to-YUV code,
which can be done now that the HDMI driver sets the bus format.
- A whole bunch of Rockchip VOP2 fixes.
- Link to v4: https://lore.kernel.org/r/20251117-color-format-v4-0-0ded72bd1b00@collabora.com
Changes in v4:
- Rebase onto next-20251117
- Get rid of HDMI_COLORSPACE_AUTO
- Split hdmi_compute_config change into separate patch
- Add missing symbol export for color_format_to_hdmi_colorspace to fix
builds in certain configurations
- Drop "drm: Pass supported color formats straight onto drm_bridge"
- Make dw-hdmi-qp set the platform data's supported color formats as
the bridge's supported HDMI color formats
- drm_hdmi_state_helper: pass requested color format to
hdmi_compute_format_bpc if set.
- drm_bridge: limit the bus formats to those explicitly requested with
the color format property during the atomic bridge check call,
specifically in drm_atomic_bridge_chain_select_bus_fmts.
- i915: Remove INTEL_OUTPUT_FORMAT_AUTO, as automatic format selection
does not need to involve the hardware state
- i915: Deduplicate ntel_output_format_to_drm_color_format code by
moving it as a static inline __pure function into a shared header
- i915: rework logic in HDMI, DP and DP-MST output config functions to
remove redundant locals, simplify execution flow, and return an error
to userspace if an explicit color_format request can't be satisfied.
- i915: assign myself as the author and make the others Co-developers,
so that they don't get the blame for any of my bugs.
- amdgpu: refactor fill_stream_properties_from_drm_display_mode to
improve readability and ensure that impossible color format requests
get bubbled up to userspace as errors
- amdgpu: don't pick YUV444 over RGB.
- amdgpu: assign authorship to myself, with others as Co-developers, as
logic was modified and the blame should fall on me
- dw_hdmi_qp-rockchip: set the supported color formats platform data
member
- rockchip: remove drm property registration for rk3066_hdmi and
inno_hdmi. None of the platforms that use these use vop2 as the
video output processor.
- Link to v3: https://lore.kernel.org/all/20250911130739.4936-1-marius.vlad@collabora.com/
Changes in v3 by mvlad compared to Andri's v2 series:
- renamed the property to just 'color format'
- the property is added dynamically similar to the Colorspace property
- a key point from previous comments was that drivers should advertise
the color formats they support and userspace would query EDID and
perform an intersection from those color formats which users can
further use. With this patch set each driver that adds this property
has such list of hard-coded color formats, but fundamentally the idea
is that driver can query the HW and do that on its own. The
infrastructure is now in place to allow to do that
- by default the 'AUTO' color format is set. With this patch series that
has been introduced as a fallback to RGB. Drivers could further
customize this behavour and could perform additional checks on the sink
to pick another suitable color format they'd like for AUTO
- drm_bridge bridge code has been improved to allow initialization with
the same color formats list as the DRM connector property. Similarly, bpc
pick-up now takes the color format into consideration when deciding
which bpc to choose from
- The new DRM color format re-uses HDMI_COLORPSACE enum and provides an
enum translations between the two to avoid touching all other drivers that
use HDMI_COLORPSACE enum. I believe at this point that this allows the
least amount of disruption and avoids a massive bike shedding around
that part
- a rockchip implementation has been by my colleague Derek Foreman
- YUV444 color format has been added in i915
- address comment about "Remove unnecessary SIGNAL_TYPE_HDMI_TYPE_A
check" where aconnector might be invalid
- Link to v2: https://lore.kernel.org/dri-devel/20240115160554.720247-1-andri@yngvason.is/
---
Andri Yngvason (1):
drm: Add new general DRM property "color format"
Nicolas Frattaroli (17):
drm/bridge: Act on the DRM color format property
drm/display: hdmi-state-helper: Act on color format DRM property
drm/display: hdmi-state-helper: Try subsampling in mode_valid
drm/i915: Implement the "color format" DRM property
drm/amdgpu: Implement "color format" DRM property
drm/rockchip: Add YUV422 output mode constants for VOP2
drm/rockchip: vop2: Add RK3576 to the RG swap special case
drm/rockchip: vop2: Recognise 10-bit YUV422 as YUV format
drm/rockchip: vop2: Set correct output format for RK3576 YUV422
drm/bridge: dw-hdmi-qp: Implement atomic_get_output_bus_fmts
drm/rockchip: dw_hdmi_qp: Implement "color format" DRM property
drm/rockchip: dw_hdmi_qp: Set supported_formats platdata
drm/connector: Register color format property on HDMI connectors
drm/tests: hdmi: Add tests for the color_format property
drm/tests: hdmi: Add tests for HDMI helper's mode_valid
drm/tests: bridge: Add KUnit tests for bridge chain format selection
drm/bridge: Document bridge chain format selection
Werner Sembach (1):
drm/amd/display: Remove unnecessary SIGNAL_TYPE_HDMI_TYPE_A check
Documentation/gpu/drm-kms-helpers.rst | 6 +
drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c | 90 ++-
.../amd/display/amdgpu_dm/amdgpu_dm_mst_types.c | 13 +
drivers/gpu/drm/bridge/synopsys/dw-hdmi-qp.c | 64 ++
drivers/gpu/drm/display/drm_hdmi_state_helper.c | 43 +-
drivers/gpu/drm/drm_atomic_helper.c | 5 +
drivers/gpu/drm/drm_atomic_uapi.c | 11 +
drivers/gpu/drm/drm_bridge.c | 129 +++-
drivers/gpu/drm/drm_connector.c | 127 ++++
drivers/gpu/drm/i915/display/intel_connector.c | 11 +
drivers/gpu/drm/i915/display/intel_connector.h | 1 +
drivers/gpu/drm/i915/display/intel_dp.c | 71 +-
drivers/gpu/drm/i915/display/intel_dp.h | 4 +
drivers/gpu/drm/i915/display/intel_dp_mst.c | 55 +-
drivers/gpu/drm/i915/display/intel_hdmi.c | 72 +-
drivers/gpu/drm/rockchip/dw_hdmi_qp-rockchip.c | 111 ++-
drivers/gpu/drm/rockchip/rockchip_drm_drv.h | 4 +
drivers/gpu/drm/rockchip/rockchip_drm_vop2.c | 21 +-
drivers/gpu/drm/tests/drm_bridge_test.c | 787 +++++++++++++++++++++
drivers/gpu/drm/tests/drm_hdmi_state_helper_test.c | 345 +++++++++
include/drm/drm_connector.h | 103 +++
21 files changed, 2018 insertions(+), 55 deletions(-)
---
base-commit: a5ccd35ff3ac42d49a4a857195577887ac9667c8
change-id: 20251028-color-format-49fd202b7183
prerequisite-change-id: 20260224-drm-rework-color-formats-82dcccc13c11:v2
prerequisite-patch-id: fbf602b97d4e1bda1f812fe036fa1295d34a7a33
prerequisite-patch-id: 83eeae76222fad7c1908f81e2694fb7f72bff980
prerequisite-patch-id: c08f10ed86f847d27f4843284a0f523e0b5c198f
prerequisite-patch-id: f88f789b3f3b19a48469c5fe1d17205772d1ca1e
prerequisite-patch-id: 1e6c3b33758ffd36bda067da90f7187e5d27db20
prerequisite-patch-id: db784a1fb0c758558bd17270c5239b95c7e1cda6
prerequisite-patch-id: 970fbdd9b5e213b06e0ac2e73267d65f567fbe04
prerequisite-patch-id: d089ecfea90265df04cb4e6d1eb79a987f5ab2d9
prerequisite-patch-id: 7ffda67d2082589a261ffe5d0f17b1e7d52b8a2d
prerequisite-patch-id: f2b0997150dac43608710dc3328e5ebcdc97992c
prerequisite-patch-id: c4f19af08ec3d6be8f2f5ce8bf7c9a192a6e7514
prerequisite-patch-id: 4c712770a76ea130539dd18d76425f22ca9e3f92
prerequisite-patch-id: 27ca247ea9f3b9fe1ec89af7ceef8dc3c67631c9
prerequisite-patch-id: f293289278bdcb8e813046e2d2af26e6c6a25fb3
Best regards,
--
Nicolas Frattaroli <nicolas.frattaroli at collabora.com>
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