[Intel-gfx] Does the intel driver support faking a connected monitor?

[Paul Gardiner]

On 09/12/2020 10:19, Jani Nikula wrote:
> On Fri, 04 Dec 2020, Paul Gardiner <lists at glidos.net> wrote:
>> On 24/11/2020 15:03, Paul Gardiner wrote:
>>> On 23/11/2020 16:19, Jani Nikula wrote:
>>>> On Sat, 21 Nov 2020, Paul Gardiner <lists at glidos.net> wrote:
>>>>> On 17/11/2020 14:52, Jani Nikula wrote:
>>>>>> On Thu, 29 Oct 2020, Paul Gardiner <lists at glidos.net> wrote:
>>>>>>> I use an open source DVR called MythTV. I've just swapped from using
>>>>>>> nvidia graphics to intel graphics. Generally it's working great, but
>>>>>>> I've run into one thing I used to do with the old system that I cannot
>>>>>>> find out how to achieve with the new.
>>>>>>>
>>>>>>> MythTV doesn't currently entirely handle starting without a TV
>>>>>>> connected. With nvidia graphics I could specify, within the X config,
>>>>>>> the "ConnectMonitor" and "CustomEDID" options to fool MythTV into
>>>>>>> thinking there was a TV. With intel graphics I can load EDID, but
>>>>>>> so far
>>>>>>> I haven't discovered an equivalent of the "ConnectedMonitor" option.
>>>>>>
>>>>>> Sorry for the delay, I seem to have missed this.
>>>>>>
>>>>>> Please try a kernel command-line parameter to force enable the
>>>>>> connector.
>>>>>>
>>>>>> video=TV-1:e
>>>>>>
>>>>>> Assuming the connector name is "TV-1"; replace with whatever you have.
>>>>>
>>>>>
>>>>> Thanks for the reply. I gave that a try, in my case "video=HDMI1:e", but
>>>>> saw no difference. That's KMS, right? Is there anything I might have
>>>>> failed to install or enable that KMS relies on? Are there any logs I
>>>>> should monitor?
>>>>
>>>> I think it should probably be HDMI-1 with the hyphen; is that a typo
>>>> above or in the command line you used?
>>>
>>> Thanks for the continued help. I tried "video=HDMI1:e" because my Xorg
>>> log listed outputs HDMI1, HDMI2, DP1 and VIRTUAL1. I've now tried
>>> "video=HDMI-1:e", but still no luck.
>>
>> Not wishing to hassle you, but before I give up, any further thoughts on
>> this?  I have a solution at least, which is to use a EDID emulator, so
>> it's no great inconvenience how it is.
> 
> This should work. ISTR it's been used before by MythTV users. (I don't
> know what you refer to with EDID emulator.)
> 
> Please file a bug over at [1]. Add drm.debug=14 module parameter, and
> attach full dmesg from boot to reproducing the problem in the bug.
> 
> BR,
> Jani.
> 
> 
> [1] https://gitlab.freedesktop.org/drm/intel/-/issues/new

The debug output was sufficient to track down the problem. It turned out 
that the connection was called HDMI-A-1. When I used that name your 
previous suggestion worked. To get exactly the behaviour I wanted I 
needed to also load EDID. This is the extra boot command string I'm using:

     drm.edid_firmware=HDMI-A-1:edid/marantz_edid.bin video=HDMI-A-1:D


For that to work I also had to ensure the referenced edid file was in my 
initramfs.

Thanks again for the help.

By the way, an EDID emulator is a small USB-stick-sized device that sits 
in between computer and monitor and acts like a monitor when the actual 
monitor is off.