On 12/03/2025 14:39, Maxime Ripard wrote:
> edid-decode gained recently support to check that infoframes are
> compliant and match the EDID the monitor exposes.
> 
> Since the HDMI helpers provide those infoframes in debugfs, it makes it
> easy to check from userspace that the drivers (and helpers) behave
> properly.
> 
> Let's document it.
> 
> Cc: Hans Verkuil <hverk...@xs4all.nl>

Reviewed-by: Hans Verkuil <hverk...@xs4all.nl>

Thanks!

        Hans

> Signed-off-by: Maxime Ripard <mrip...@kernel.org>
> ---
>  drivers/gpu/drm/display/drm_hdmi_state_helper.c | 271 
> ++++++++++++++++++++++++
>  1 file changed, 271 insertions(+)
> 
> diff --git a/drivers/gpu/drm/display/drm_hdmi_state_helper.c 
> b/drivers/gpu/drm/display/drm_hdmi_state_helper.c
> index 
> 24bfc82bf9b02bf3201d97432e3c239ccc8714b4..4df3d25529071e8e822f1fe00fb22c90860ec97b
>  100644
> --- a/drivers/gpu/drm/display/drm_hdmi_state_helper.c
> +++ b/drivers/gpu/drm/display/drm_hdmi_state_helper.c
> @@ -16,10 +16,281 @@
>   * in the form of KMS helpers.
>   *
>   * It contains TMDS character rate computation, automatic selection of
>   * output formats, infoframes generation, etc.
>   *
> + * Infoframes Compliance
> + * ~~~~~~~~~~~~~~~~~~~~~
> + *
> + * Drivers using the helpers will expose the various infoframes
> + * generated according to the HDMI specification in debugfs.
> + *
> + * Compliance can then be tested using ``edid-decode`` from the 
> ``v4l-utils`` project
> + * (https://git.linuxtv.org/v4l-utils.git/). A sample run would look like:
> + *
> + * .. code-block:: bash
> + *
> + *   # edid-decode \
> + *           -I /sys/kernel/debug/dri/1/HDMI-A-1/infoframes/audio \
> + *           -I /sys/kernel/debug/dri/1/HDMI-A-1/infoframes/avi \
> + *           -I /sys/kernel/debug/dri/1/HDMI-A-1/infoframes/hdmi \
> + *           -I /sys/kernel/debug/dri/1/HDMI-A-1/infoframes/hdr_drm \
> + *           -I /sys/kernel/debug/dri/1/HDMI-A-1/infoframes/spd \
> + *           /sys/class/drm/card1-HDMI-A-1/edid \
> + *           -c
> + *
> + *   edid-decode (hex):
> + *
> + *   00 ff ff ff ff ff ff 00 1e 6d f4 5b 1e ef 06 00
> + *   07 20 01 03 80 2f 34 78 ea 24 05 af 4f 42 ab 25
> + *   0f 50 54 21 08 00 d1 c0 61 40 45 40 01 01 01 01
> + *   01 01 01 01 01 01 98 d0 00 40 a1 40 d4 b0 30 20
> + *   3a 00 d1 0b 12 00 00 1a 00 00 00 fd 00 3b 3d 1e
> + *   b2 31 00 0a 20 20 20 20 20 20 00 00 00 fc 00 4c
> + *   47 20 53 44 51 48 44 0a 20 20 20 20 00 00 00 ff
> + *   00 32 30 37 4e 54 52 4c 44 43 34 33 30 0a 01 46
> + *
> + *   02 03 42 72 23 09 07 07 4d 01 03 04 90 12 13 1f
> + *   22 5d 5e 5f 60 61 83 01 00 00 6d 03 0c 00 10 00
> + *   b8 3c 20 00 60 01 02 03 67 d8 5d c4 01 78 80 03
> + *   e3 0f 00 18 e2 00 6a e3 05 c0 00 e6 06 05 01 52
> + *   52 51 11 5d 00 a0 a0 40 29 b0 30 20 3a 00 d1 0b
> + *   12 00 00 1a 00 00 00 00 00 00 00 00 00 00 00 00
> + *   00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
> + *   00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 c3
> + *
> + *   ----------------
> + *
> + *   Block 0, Base EDID:
> + *     EDID Structure Version & Revision: 1.3
> + *     Vendor & Product Identification:
> + *       Manufacturer: GSM
> + *       Model: 23540
> + *       Serial Number: 454430 (0x0006ef1e)
> + *       Made in: week 7 of 2022
> + *     Basic Display Parameters & Features:
> + *       Digital display
> + *       Maximum image size: 47 cm x 52 cm
> + *       Gamma: 2.20
> + *       DPMS levels: Standby Suspend Off
> + *       RGB color display
> + *       First detailed timing is the preferred timing
> + *     Color Characteristics:
> + *       Red  : 0.6835, 0.3105
> + *       Green: 0.2587, 0.6679
> + *       Blue : 0.1445, 0.0585
> + *       White: 0.3134, 0.3291
> + *     Established Timings I & II:
> + *       DMT 0x04:   640x480    59.940476 Hz   4:3     31.469 kHz     
> 25.175000 MHz
> + *       DMT 0x09:   800x600    60.316541 Hz   4:3     37.879 kHz     
> 40.000000 MHz
> + *       DMT 0x10:  1024x768    60.003840 Hz   4:3     48.363 kHz     
> 65.000000 MHz
> + *     Standard Timings:
> + *       DMT 0x52:  1920x1080   60.000000 Hz  16:9     67.500 kHz    
> 148.500000 MHz
> + *       DMT 0x10:  1024x768    60.003840 Hz   4:3     48.363 kHz     
> 65.000000 MHz
> + *       DMT 0x09:   800x600    60.316541 Hz   4:3     37.879 kHz     
> 40.000000 MHz
> + *     Detailed Timing Descriptors:
> + *       DTD 1:  2560x2880   59.966580 Hz   8:9    185.417 kHz    534.000000 
> MHz (465 mm x 523 mm)
> + *                    Hfront   48 Hsync  32 Hback  240 Hpol P
> + *                    Vfront    3 Vsync  10 Vback  199 Vpol N
> + *       Display Range Limits:
> + *         Monitor ranges (GTF): 59-61 Hz V, 30-178 kHz H, max dotclock 490 
> MHz
> + *       Display Product Name: 'LG SDQHD'
> + *       Display Product Serial Number: '207NTRLDC430'
> + *     Extension blocks: 1
> + *   Checksum: 0x46
> + *
> + *   ----------------
> + *
> + *   Block 1, CTA-861 Extension Block:
> + *     Revision: 3
> + *     Basic audio support
> + *     Supports YCbCr 4:4:4
> + *     Supports YCbCr 4:2:2
> + *     Native detailed modes: 2
> + *     Audio Data Block:
> + *       Linear PCM:
> + *         Max channels: 2
> + *         Supported sample rates (kHz): 48 44.1 32
> + *         Supported sample sizes (bits): 24 20 16
> + *     Video Data Block:
> + *       VIC   1:   640x480    59.940476 Hz   4:3     31.469 kHz     
> 25.175000 MHz
> + *       VIC   3:   720x480    59.940060 Hz  16:9     31.469 kHz     
> 27.000000 MHz
> + *       VIC   4:  1280x720    60.000000 Hz  16:9     45.000 kHz     
> 74.250000 MHz
> + *       VIC  16:  1920x1080   60.000000 Hz  16:9     67.500 kHz    
> 148.500000 MHz (native)
> + *       VIC  18:   720x576    50.000000 Hz  16:9     31.250 kHz     
> 27.000000 MHz
> + *       VIC  19:  1280x720    50.000000 Hz  16:9     37.500 kHz     
> 74.250000 MHz
> + *       VIC  31:  1920x1080   50.000000 Hz  16:9     56.250 kHz    
> 148.500000 MHz
> + *       VIC  34:  1920x1080   30.000000 Hz  16:9     33.750 kHz     
> 74.250000 MHz
> + *       VIC  93:  3840x2160   24.000000 Hz  16:9     54.000 kHz    
> 297.000000 MHz
> + *       VIC  94:  3840x2160   25.000000 Hz  16:9     56.250 kHz    
> 297.000000 MHz
> + *       VIC  95:  3840x2160   30.000000 Hz  16:9     67.500 kHz    
> 297.000000 MHz
> + *       VIC  96:  3840x2160   50.000000 Hz  16:9    112.500 kHz    
> 594.000000 MHz
> + *       VIC  97:  3840x2160   60.000000 Hz  16:9    135.000 kHz    
> 594.000000 MHz
> + *     Speaker Allocation Data Block:
> + *       FL/FR - Front Left/Right
> + *     Vendor-Specific Data Block (HDMI), OUI 00-0C-03:
> + *       Source physical address: 1.0.0.0
> + *       Supports_AI
> + *       DC_36bit
> + *       DC_30bit
> + *       DC_Y444
> + *       Maximum TMDS clock: 300 MHz
> + *       Extended HDMI video details:
> + *         HDMI VICs:
> + *           HDMI VIC 1:  3840x2160   30.000000 Hz  16:9     67.500 kHz    
> 297.000000 MHz
> + *           HDMI VIC 2:  3840x2160   25.000000 Hz  16:9     56.250 kHz    
> 297.000000 MHz
> + *           HDMI VIC 3:  3840x2160   24.000000 Hz  16:9     54.000 kHz    
> 297.000000 MHz
> + *     Vendor-Specific Data Block (HDMI Forum), OUI C4-5D-D8:
> + *       Version: 1
> + *       Maximum TMDS Character Rate: 600 MHz
> + *       SCDC Present
> + *       Supports 12-bits/component Deep Color 4:2:0 Pixel Encoding
> + *       Supports 10-bits/component Deep Color 4:2:0 Pixel Encoding
> + *     YCbCr 4:2:0 Capability Map Data Block:
> + *       VIC  96:  3840x2160   50.000000 Hz  16:9    112.500 kHz    
> 594.000000 MHz
> + *       VIC  97:  3840x2160   60.000000 Hz  16:9    135.000 kHz    
> 594.000000 MHz
> + *     Video Capability Data Block:
> + *       YCbCr quantization: No Data
> + *       RGB quantization: Selectable (via AVI Q)
> + *       PT scan behavior: Always Underscanned
> + *       IT scan behavior: Always Underscanned
> + *       CE scan behavior: Always Underscanned
> + *     Colorimetry Data Block:
> + *       BT2020YCC
> + *       BT2020RGB
> + *     HDR Static Metadata Data Block:
> + *       Electro optical transfer functions:
> + *         Traditional gamma - SDR luminance range
> + *         SMPTE ST2084
> + *       Supported static metadata descriptors:
> + *         Static metadata type 1
> + *       Desired content max luminance: 82 (295.365 cd/m^2)
> + *       Desired content max frame-average luminance: 82 (295.365 cd/m^2)
> + *       Desired content min luminance: 81 (0.298 cd/m^2)
> + *     Detailed Timing Descriptors:
> + *       DTD 2:  2560x2880   29.986961 Hz   8:9     87.592 kHz    238.250000 
> MHz (465 mm x 523 mm)
> + *                    Hfront   48 Hsync  32 Hback   80 Hpol P
> + *                    Vfront    3 Vsync  10 Vback   28 Vpol N
> + *   Checksum: 0xc3  Unused space in Extension Block: 43 bytes
> + *
> + *   ----------------
> + *
> + *   edid-decode 1.29.0-5346
> + *   edid-decode SHA: c363e9aa6d70 2025-03-11 11:41:18
> + *
> + *   Warnings:
> + *
> + *   Block 1, CTA-861 Extension Block:
> + *     IT Video Formats are overscanned by default, but normally this should 
> be underscanned.
> + *     Video Data Block: VIC 1 and the first DTD are not identical. Is this 
> intended?
> + *     Video Data Block: All VICs are in ascending order, and the first 
> (preferred) VIC <= 4, is that intended?
> + *     Video Capability Data Block: Set Selectable YCbCr Quantization to 
> avoid interop issues.
> + *     Video Capability Data Block: S_PT is equal to S_IT and S_CE, so 
> should be set to 0 instead.
> + *     Colorimetry Data Block: Set the sRGB colorimetry bit to avoid interop 
> issues.
> + *     Display Product Serial Number is set, so the Serial Number in the 
> Base EDID should be 0.
> + *   EDID:
> + *     Base EDID: Some timings are out of range of the Monitor Ranges:
> + *       Vertical Freq: 24.000 - 60.317 Hz (Monitor: 59.000 - 61.000 Hz)
> + *       Horizontal Freq: 31.250 - 185.416 kHz (Monitor: 30.000 - 178.000 
> kHz)
> + *       Maximum Clock: 594.000 MHz (Monitor: 490.000 MHz)
> + *
> + *   Failures:
> + *
> + *   Block 1, CTA-861 Extension Block:
> + *     Video Capability Data Block: IT video formats are always 
> underscanned, but bit 7 of Byte 3 of the CTA-861 Extension header is set to 
> overscanned.
> + *   EDID:
> + *     CTA-861: Native progressive timings are a mix of several resolutions.
> + *
> + *   EDID conformity: FAIL
> + *
> + *   ================
> + *
> + *   InfoFrame of '/sys/kernel/debug/dri/1/HDMI-A-1/infoframes/audio' was 
> empty.
> + *
> + *   ================
> + *
> + *   edid-decode InfoFrame (hex):
> + *
> + *   82 02 0d 31 12 28 04 00 00 00 00 00 00 00 00 00
> + *   00
> + *
> + *   ----------------
> + *
> + *   HDMI InfoFrame Checksum: 0x31
> + *
> + *   AVI InfoFrame
> + *     Version: 2
> + *     Length: 13
> + *     Y: Color Component Sample Format: RGB
> + *     A: Active Format Information Present: Yes
> + *     B: Bar Data Present: Bar Data not present
> + *     S: Scan Information: Composed for an underscanned display
> + *     C: Colorimetry: No Data
> + *     M: Picture Aspect Ratio: 16:9
> + *     R: Active Portion Aspect Ratio: 8
> + *     ITC: IT Content: No Data
> + *     EC: Extended Colorimetry: xvYCC601
> + *     Q: RGB Quantization Range: Limited Range
> + *     SC: Non-Uniform Picture Scaling: No Known non-uniform scaling
> + *     YQ: YCC Quantization Range: Limited Range
> + *     CN: IT Content Type: Graphics
> + *     PR: Pixel Data Repetition Count: 0
> + *     Line Number of End of Top Bar: 0
> + *     Line Number of Start of Bottom Bar: 0
> + *     Pixel Number of End of Left Bar: 0
> + *     Pixel Number of Start of Right Bar: 0
> + *
> + *   ----------------
> + *
> + *   AVI InfoFrame conformity: PASS
> + *
> + *   ================
> + *
> + *   edid-decode InfoFrame (hex):
> + *
> + *   81 01 05 49 03 0c 00 20 01
> + *
> + *   ----------------
> + *
> + *   HDMI InfoFrame Checksum: 0x49
> + *
> + *   Vendor-Specific InfoFrame (HDMI), OUI 00-0C-03
> + *     Version: 1
> + *     Length: 5
> + *     HDMI Video Format: HDMI_VIC is present
> + *     HDMI VIC 1:  3840x2160   30.000000 Hz  16:9     67.500 kHz    
> 297.000000 MHz
> + *
> + *   ----------------
> + *
> + *   Vendor-Specific InfoFrame (HDMI), OUI 00-0C-03 conformity: PASS
> + *
> + *   ================
> + *
> + *   InfoFrame of '/sys/kernel/debug/dri/1/HDMI-A-1/infoframes/hdr_drm' was 
> empty.
> + *
> + *   ================
> + *
> + *   edid-decode InfoFrame (hex):
> + *
> + *   83 01 19 93 42 72 6f 61 64 63 6f 6d 56 69 64 65
> + *   6f 63 6f 72 65 00 00 00 00 00 00 00 09
> + *
> + *   ----------------
> + *
> + *   HDMI InfoFrame Checksum: 0x93
> + *
> + *   Source Product Description InfoFrame
> + *     Version: 1
> + *     Length: 25
> + *     Vendor Name: 'Broadcom'
> + *     Product Description: 'Videocore'
> + *     Source Information: PC general
> + *
> + *   ----------------
> + *
> + *   Source Product Description InfoFrame conformity: PASS
> + *
>   * Testing
>   * ~~~~~~~
>   *
>   * The helpers have unit testing and can be tested using kunit with:
>   *
> 

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