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 <daniel.vetter@ffwll.ch>
Acked-by: Jani Nikula <jani.nikula@intel.com>
Acked-by: Pekka Paalanen <pekka.paalanen@collabora.com>
Acked-by: Thomas Zimmermann <tzimmermann@suse.de>
Signed-off-by: Maxime Ripard <mripard@kernel.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20240221092636.691701-1-mripard@kernel.org

2 files changed, 5 insertions, 44 deletions

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.
diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index 31b3a25680d0..944a11e0179d 100644
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -1162,16 +1162,10 @@
 			panels may send no or incorrect EDID data sets.
 			This parameter allows to specify an EDID data sets
 			in the /lib/firmware directory that are used instead.
-			Generic built-in EDID data sets are used, if one of
-			edid/1024x768.bin, edid/1280x1024.bin,
-			edid/1680x1050.bin, or edid/1920x1080.bin is given
-			and no file with the same name exists. Details and
-			instructions how to build your own EDID data are
-			available in Documentation/admin-guide/edid.rst. An EDID
-			data set will only be used for a particular connector,
-			if its name and a colon are prepended to the EDID
-			name. Each connector may use a unique EDID data
-			set by separating the files with a comma.  An EDID
+			An EDID data set will only be used for a particular
+			connector, if its name and a colon are prepended to
+			the EDID name. Each connector may use a unique EDID
+			data set by separating the files with a comma. An EDID
 			data set with no connector name will be used for
 			any connectors not explicitly specified.