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Re: Screen goes blank after "EDID checksum is invalid" errors

On Sun, 06 Sep 2015 08:07:32 -0400 (EDT), Sven Joachim wrote:
> On 2015-09-06 12:31 +0200, Stephen Powell wrote:
>> Some monitors have invalid EDID checksums.  Blame the manufacturer.
>> Windows is more tolerant of EDID checksum errors than Linux is.
>> If switching monitors solves your problem, then a bona fide EDID checksum
>> error in the hardware is probably to blame.  If you're willing to
>> build a custom kernel, you may be able to circumvent the problem by applying a
>> patch.  See my kernel-building web page:
>>    http://users.wowway.com/~zlinuxman/Kernel.htm
>> In "Step 7: Patch the kernel", there is a specific example of how to apply
>> this patch.  Basically, it allows you to tell the kernel to ignore EDID
>> check sum errors by using the following setting in a file with the extension
>> of ".conf" under /etc/modprobe.d:
>>    options drm edid_strict=0
>> This may allow you to use your faulty monitor anyway.  Good luck.
> I don't think this is a very good idea in this case, the EDID of
> Johannes' monitor seems to be very broken (almost all bytes are 0xff).
> Rather than patching the kernel to not complain about that, it is
> probably better to supply valid EDID data via the
> drm_kms_helper.edid_firmware option.
> The downside of this approach is that you have to supply the EDID
> file, there are several under Documentation/EDID/ in the kernel
> source (assembly source and a Makefile).

The OP said that what he included in this problem report came from
another problem report, because it scrolled off the screen too fast
for him to give actual data.  (Perhaps he doesn't know about
"dmesg|less".)  So I wouldn't give too much credence to the content
of the posted EDID data.  Nevertheless, I agree that the approach you
suggested above is a better solution, if the needed firmware file can
be found.

I didn't know about the drm kms_helper.edid option, so I've learned
something new.  Thanks, Sven.

  .''`.     Stephen Powell    <zlinuxman@wowway.com>
 : :'  :
 `. `'`

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