From 89ac522d4507126d353834973ddbbf7b6acfdeef Mon Sep 17 00:00:00 2001 From: Maxime Ripard Date: Wed, 21 Feb 2024 10:26:36 +0100 Subject: drm/edid/firmware: Remove built-in EDIDs The EDID firmware loading mechanism introduced a few built-in EDIDs that could be forced on any connector, bypassing the EDIDs it exposes. While convenient, this limited set of EDIDs doesn't take into account the connector type, and we can end up with an EDID that is completely invalid for a given connector. For example, the edid/800x600.bin file matches the following EDID: edid-decode (hex): 00 ff ff ff ff ff ff 00 31 d8 00 00 00 00 00 00 05 16 01 03 6d 1b 14 78 ea 5e c0 a4 59 4a 98 25 20 50 54 01 00 00 45 40 01 01 01 01 01 01 01 01 01 01 01 01 01 01 a0 0f 20 00 31 58 1c 20 28 80 14 00 15 d0 10 00 00 1e 00 00 00 ff 00 4c 69 6e 75 78 20 23 30 0a 20 20 20 20 00 00 00 fd 00 3b 3d 24 26 05 00 0a 20 20 20 20 20 20 00 00 00 fc 00 4c 69 6e 75 78 20 53 56 47 41 0a 20 20 00 c2 ---------------- Block 0, Base EDID: EDID Structure Version & Revision: 1.3 Vendor & Product Identification: Manufacturer: LNX Model: 0 Made in: week 5 of 2012 Basic Display Parameters & Features: Analog display Signal Level Standard: 0.700 : 0.000 : 0.700 V p-p Blank level equals black level Sync: Separate Composite Serration Maximum image size: 27 cm x 20 cm Gamma: 2.20 DPMS levels: Standby Suspend Off RGB color display First detailed timing is the preferred timing Color Characteristics: Red : 0.6416, 0.3486 Green: 0.2919, 0.5957 Blue : 0.1474, 0.1250 White: 0.3125, 0.3281 Established Timings I & II: DMT 0x09: 800x600 60.316541 Hz 4:3 37.879 kHz 40.000000 MHz Standard Timings: DMT 0x09: 800x600 60.316541 Hz 4:3 37.879 kHz 40.000000 MHz Detailed Timing Descriptors: DTD 1: 800x600 60.316541 Hz 4:3 37.879 kHz 40.000000 MHz (277 mm x 208 mm) Hfront 40 Hsync 128 Hback 88 Hpol P Vfront 1 Vsync 4 Vback 23 Vpol P Display Product Serial Number: 'Linux #0' Display Range Limits: Monitor ranges (GTF): 59-61 Hz V, 36-38 kHz H, max dotclock 50 MHz Display Product Name: 'Linux SVGA' Checksum: 0xc2 So, an analog monitor EDID. However, if the connector was an HDMI monitor for example, it breaks the HDMI specification that requires, among other things, a digital display, the VIC 1 mode and an HDMI Forum Vendor Specific Data Block in an CTA-861 extension. We thus end up with a completely invalid EDID, which thus might confuse HDMI-related code that could parse it. After some discussions on IRC, we identified mainly two ways to fix this: - We can either create more EDIDs for each connector type to provide a built-in EDID that matches the resolution passed in the name, and still be a sensible EDID for that connector type; - Or we can just prevent the EDID to be exposed to userspace if it's built-in. Or possibly both. However, the conclusion was that maybe we just don't need the built-in EDIDs at all and we should just get rid of them. So here we are. Acked-by: Daniel Vetter Acked-by: Jani Nikula Acked-by: Pekka Paalanen Acked-by: Thomas Zimmermann Signed-off-by: Maxime Ripard Link: https://patchwork.freedesktop.org/patch/msgid/20240221092636.691701-1-mripard@kernel.org --- Documentation/admin-guide/edid.rst | 35 +---------------------------------- 1 file changed, 1 insertion(+), 34 deletions(-) (limited to 'Documentation/admin-guide/edid.rst') diff --git a/Documentation/admin-guide/edid.rst b/Documentation/admin-guide/edid.rst index 80deeb21a265..1a9b965aa486 100644 --- a/Documentation/admin-guide/edid.rst +++ b/Documentation/admin-guide/edid.rst @@ -24,37 +24,4 @@ restrictions later on. As a remedy for such situations, the kernel configuration item CONFIG_DRM_LOAD_EDID_FIRMWARE was introduced. It allows to provide an individually prepared or corrected EDID data set in the /lib/firmware -directory from where it is loaded via the firmware interface. The code -(see drivers/gpu/drm/drm_edid_load.c) contains built-in data sets for -commonly used screen resolutions (800x600, 1024x768, 1280x1024, 1600x1200, -1680x1050, 1920x1080) as binary blobs, but the kernel source tree does -not contain code to create these data. In order to elucidate the origin -of the built-in binary EDID blobs and to facilitate the creation of -individual data for a specific misbehaving monitor, commented sources -and a Makefile environment are given here. - -To create binary EDID and C source code files from the existing data -material, simply type "make" in tools/edid/. - -If you want to create your own EDID file, copy the file 1024x768.S, -replace the settings with your own data and add a new target to the -Makefile. Please note that the EDID data structure expects the timing -values in a different way as compared to the standard X11 format. - -X11: - HTimings: - hdisp hsyncstart hsyncend htotal - VTimings: - vdisp vsyncstart vsyncend vtotal - -EDID:: - - #define XPIX hdisp - #define XBLANK htotal-hdisp - #define XOFFSET hsyncstart-hdisp - #define XPULSE hsyncend-hsyncstart - - #define YPIX vdisp - #define YBLANK vtotal-vdisp - #define YOFFSET vsyncstart-vdisp - #define YPULSE vsyncend-vsyncstart +directory from where it is loaded via the firmware interface. -- cgit v1.2.3