48eaeb7664
We've moved the override and firmware EDID (simply "override EDID" from now on) handling to the low level drm_do_get_edid() function in order to transparently use the override throughout the stack. The idea is that you get the override EDID via the ->get_modes() hook. Unfortunately, there are scenarios where the DDC probe in drm_get_edid() called via ->get_modes() fails, although the preceding ->detect() succeeds. In the case reported by Paul Wise, the ->detect() hook, intel_crt_detect(), relies on hotplug detect, bypassing the DDC. In the case reported by Ilpo Järvinen, there is no ->detect() hook, which is interpreted as connected. The subsequent DDC probe reached via ->get_modes() fails, and we don't even look at the override EDID, resulting in no modes being added. Because drm_get_edid() is used via ->detect() all over the place, we can't trivially remove the DDC probe, as it leads to override EDID effectively meaning connector forcing. The goal is that connector forcing and override EDID remain orthogonal. Generally, the underlying problem here is the conflation of ->detect() and ->get_modes() via drm_get_edid(). The former should just detect, and the latter should just get the modes, typically via reading the EDID. As long as drm_get_edid() is used in ->detect(), it needs to retain the DDC probe. Or such users need to have a separate DDC probe step first. The EDID caching between ->detect() and ->get_modes() done by some drivers is a further complication that prevents us from making drm_do_get_edid() adapt to the two cases. Work around the regression by falling back to a separate attempt at getting the override EDID at drm_helper_probe_single_connector_modes() level. With a working DDC and override EDID, it'll never be called; the override EDID will come via ->get_modes(). There will still be a failing DDC probe attempt in the cases that require the fallback. v2: - Call drm_connector_update_edid_property (Paul) - Update commit message about EDID caching (Daniel) Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=107583 Reported-by: Paul Wise <pabs3@bonedaddy.net> Cc: Paul Wise <pabs3@bonedaddy.net> References: http://mid.mail-archive.com/alpine.DEB.2.20.1905262211270.24390@whs-18.cs.helsinki.fi Reported-by: Ilpo Järvinen <ilpo.jarvinen@cs.helsinki.fi> Cc: Ilpo Järvinen <ilpo.jarvinen@cs.helsinki.fi> Suggested-by: Daniel Vetter <daniel.vetter@ffwll.ch> References: |
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README
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.