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linux-stable/Documentation/admin-guide/edid.rst

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docs: driver-api: add a series of orphaned documents There are lots of documents under Documentation/*.txt and a few other orphan documents elsehwere that belong to the driver-API book. Move them to their right place. Reviewed-by: Cornelia Huck <cohuck@redhat.com> # vfio-related parts Acked-by: Logan Gunthorpe <logang@deltatee.com> # switchtec Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>
2019-06-27 18:39:22 +00:00
.. SPDX-License-Identifier: GPL-2.0
docs: EDID/HOWTO.txt: convert it and rename to howto.rst Sphinx need to know when a paragraph ends. So, do some adjustments at the file for it to be properly parsed. At its new index.rst, let's add a :orphan: while this is not linked to the main index.rst file, in order to avoid build warnings. that's said, I believe that this file should be moved to the GPU/DRM documentation. Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org> Signed-off-by: Jonathan Corbet <corbet@lwn.net>
2019-06-12 17:53:04 +00:00
====
EDID
====
drm: allow loading an EDID as firmware to override broken monitor Broken monitors and/or broken graphic boards may send erroneous or no EDID data. This also applies to broken KVM devices that are unable to correctly forward the EDID data of the connected monitor but invent their own fantasy data. This patch allows to specify an EDID data set to be used instead of probing the monitor for it. It contains built-in data sets of frequently used screen resolutions. In addition, a particular EDID data set may be provided in the /lib/firmware directory and loaded via the firmware interface. The name is passed to the kernel as module parameter of the drm_kms_helper module either when loaded options drm_kms_helper edid_firmware=edid/1280x1024.bin or as kernel commandline parameter drm_kms_helper.edid_firmware=edid/1280x1024.bin It is also possible to restrict the usage of a specified EDID data set to a particular connector. This is done by prepending the name of the connector to the name of the EDID data set using the syntax edid_firmware=[<connector>:]<edid> such as, for example, edid_firmware=DVI-I-1:edid/1920x1080.bin in which case no other connector will be affected. The built-in data sets are Resolution Name -------------------------------- 1024x768 edid/1024x768.bin 1280x1024 edid/1280x1024.bin 1680x1050 edid/1680x1050.bin 1920x1080 edid/1920x1080.bin They are ignored, if a file with the same name is available in the /lib/firmware directory. The built-in EDID data sets are based on standard timings that may not apply to a particular monitor and even crash it. Ideally, EDID data of the connected monitor should be used. They may be obtained through the drm/cardX/cardX-<connector>/edid entry in the /sys/devices PCI directory of a correctly working graphics adapter. It is even possible to specify the name of an EDID data set on-the-fly via the /sys/module interface, e.g. echo edid/myedid.bin >/sys/module/drm_kms_helper/parameters/edid_firmware The new screen mode is considered when the related kernel function is called for the first time after the change. Such calls are made when the X server is started or when the display settings dialog is opened in an already running X server. Signed-off-by: Carsten Emde <C.Emde@osadl.org> Signed-off-by: Dave Airlie <airlied@redhat.com>
2012-03-18 21:37:33 +00:00
In the good old days when graphics parameters were configured explicitly
in a file called xorg.conf, even broken hardware could be managed.
Today, with the advent of Kernel Mode Setting, a graphics board is
either correctly working because all components follow the standards -
or the computer is unusable, because the screen remains dark after
booting or it displays the wrong area. Cases when this happens are:
docs: driver-api: edid: Fix list formatting Without the empty lines, Sphinx renders the list as part of the running text. Signed-off-by: Jonathan Neuschäfer <j.neuschaefer@gmx.net> Signed-off-by: Jonathan Corbet <corbet@lwn.net>
2020-02-14 17:41:32 +00:00
drm: allow loading an EDID as firmware to override broken monitor Broken monitors and/or broken graphic boards may send erroneous or no EDID data. This also applies to broken KVM devices that are unable to correctly forward the EDID data of the connected monitor but invent their own fantasy data. This patch allows to specify an EDID data set to be used instead of probing the monitor for it. It contains built-in data sets of frequently used screen resolutions. In addition, a particular EDID data set may be provided in the /lib/firmware directory and loaded via the firmware interface. The name is passed to the kernel as module parameter of the drm_kms_helper module either when loaded options drm_kms_helper edid_firmware=edid/1280x1024.bin or as kernel commandline parameter drm_kms_helper.edid_firmware=edid/1280x1024.bin It is also possible to restrict the usage of a specified EDID data set to a particular connector. This is done by prepending the name of the connector to the name of the EDID data set using the syntax edid_firmware=[<connector>:]<edid> such as, for example, edid_firmware=DVI-I-1:edid/1920x1080.bin in which case no other connector will be affected. The built-in data sets are Resolution Name -------------------------------- 1024x768 edid/1024x768.bin 1280x1024 edid/1280x1024.bin 1680x1050 edid/1680x1050.bin 1920x1080 edid/1920x1080.bin They are ignored, if a file with the same name is available in the /lib/firmware directory. The built-in EDID data sets are based on standard timings that may not apply to a particular monitor and even crash it. Ideally, EDID data of the connected monitor should be used. They may be obtained through the drm/cardX/cardX-<connector>/edid entry in the /sys/devices PCI directory of a correctly working graphics adapter. It is even possible to specify the name of an EDID data set on-the-fly via the /sys/module interface, e.g. echo edid/myedid.bin >/sys/module/drm_kms_helper/parameters/edid_firmware The new screen mode is considered when the related kernel function is called for the first time after the change. Such calls are made when the X server is started or when the display settings dialog is opened in an already running X server. Signed-off-by: Carsten Emde <C.Emde@osadl.org> Signed-off-by: Dave Airlie <airlied@redhat.com>
2012-03-18 21:37:33 +00:00
- The graphics board does not recognize the monitor.
- The graphics board is unable to detect any EDID data.
- The graphics board incorrectly forwards EDID data to the driver.
- The monitor sends no or bogus EDID data.
- A KVM sends its own EDID data instead of querying the connected monitor.
docs: driver-api: edid: Fix list formatting Without the empty lines, Sphinx renders the list as part of the running text. Signed-off-by: Jonathan Neuschäfer <j.neuschaefer@gmx.net> Signed-off-by: Jonathan Corbet <corbet@lwn.net>
2020-02-14 17:41:32 +00:00
drm: allow loading an EDID as firmware to override broken monitor Broken monitors and/or broken graphic boards may send erroneous or no EDID data. This also applies to broken KVM devices that are unable to correctly forward the EDID data of the connected monitor but invent their own fantasy data. This patch allows to specify an EDID data set to be used instead of probing the monitor for it. It contains built-in data sets of frequently used screen resolutions. In addition, a particular EDID data set may be provided in the /lib/firmware directory and loaded via the firmware interface. The name is passed to the kernel as module parameter of the drm_kms_helper module either when loaded options drm_kms_helper edid_firmware=edid/1280x1024.bin or as kernel commandline parameter drm_kms_helper.edid_firmware=edid/1280x1024.bin It is also possible to restrict the usage of a specified EDID data set to a particular connector. This is done by prepending the name of the connector to the name of the EDID data set using the syntax edid_firmware=[<connector>:]<edid> such as, for example, edid_firmware=DVI-I-1:edid/1920x1080.bin in which case no other connector will be affected. The built-in data sets are Resolution Name -------------------------------- 1024x768 edid/1024x768.bin 1280x1024 edid/1280x1024.bin 1680x1050 edid/1680x1050.bin 1920x1080 edid/1920x1080.bin They are ignored, if a file with the same name is available in the /lib/firmware directory. The built-in EDID data sets are based on standard timings that may not apply to a particular monitor and even crash it. Ideally, EDID data of the connected monitor should be used. They may be obtained through the drm/cardX/cardX-<connector>/edid entry in the /sys/devices PCI directory of a correctly working graphics adapter. It is even possible to specify the name of an EDID data set on-the-fly via the /sys/module interface, e.g. echo edid/myedid.bin >/sys/module/drm_kms_helper/parameters/edid_firmware The new screen mode is considered when the related kernel function is called for the first time after the change. Such calls are made when the X server is started or when the display settings dialog is opened in an already running X server. Signed-off-by: Carsten Emde <C.Emde@osadl.org> Signed-off-by: Dave Airlie <airlied@redhat.com>
2012-03-18 21:37:33 +00:00
Adding the kernel parameter "nomodeset" helps in most cases, but causes
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
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
2024-02-21 09:26:36 +00:00
directory from where it is loaded via the firmware interface.