[Openchrome-devel] [Bug 91966] No signal to monitor with X and openchrome using VX855 chipset graphics

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=91966

--- Comment #203 from HuangRan <huangran at iscas.ac.cn> ---
Hi Kevin,



         Glad to receive your response so quickly.

         For I2C probe EDID information, generally there are several the I2C HW
pair lines as you said. And they can be routed to VGA connector/DVI connector,
even for HDMI connector. It depends on HW schematic. 

         So for this Wyse C90LE case, do we know which I2C HW pair lines are
used for chipset? If there is no EDID information probed out, we can try a
fixed mode to see if that is the reason for this issue. I know how to do it in
DRM instead of UMS driver. And I think there is a way to try a fixed mode in
UMS driver too.



Thanks,

Frank



发件人: Openchrome-devel [mailto:openchrome-devel-bounces at lists.freedesktop.org]
代表 bugzilla-daemon at freedesktop.org
发送时间: 2016年2月22日 17:36
收件人: openchrome-devel at lists.freedesktop.org
主题: [Openchrome-devel] [Bug 91966] No signal to monitor with X and openchrome
using VX855 chipset graphics



Comment # 202 <https://bugs.freedesktop.org/show_bug.cgi?id=91966#c202>  on bug
91966 <https://bugs.freedesktop.org/show_bug.cgi?id=91966>  from 
<mailto:kevinbrace at gmx.com> Kevin Brace 

(In reply to HuangRan from comment #201
<https://bugs.freedesktop.org/show_bug.cgi?id=91966#c201> )

Hi Frank,

> Hi Guys,
> 
>    Returning from my holiday and looking at this thread from the start to
> the end takes me several hours to do so although I have to skip some content
> for your chat becuase it is so long.
>    As I replied the mail to Kevin, I prefer to put my more time on
> OpenChrome and has several guys invovled on this project. So I hope I can
> provide some useful informaiton on this bug too.
>    So is this bug fixed or not? Does I2C 2 probe EDID information from DVI
> interface?
> 
> Thanks,
> Frank

The way the code works right now with the patch is that I2C bus 1 and 2 are
used for VGA related monitor detection.
xserver's API returns a structure that tells the caller if the monitor type is
analog or digital.
I use this information to see if I2C bus 1 or 2 is connected to an analog
monitor (i.e., VGA monitor).
I read the Intel DDX UMS code, and they apparently do this.
As for DVI, I2C bus 2 or 3 are used for communicating with the monitor and an
external TMDS transmitter chip.
In other words, I2C bus 2 can be used for VGA, DVI, or even a TV encoder chip.
The code that handles an external TMDS transmitter for DVI (i.e., VT1632A chip)
is still relatively unproven.
It was donated in early 2015, but there was a bug in it, and I help fix it with
the person who reported it (Bug 93675
<https://bugs.freedesktop.org/show_bug.cgi?id=93675> ).
I do own about 10 or so VIA Technologies IGP based mainboards / computers at my
place, but I do not really have a functional mainboard / computer with DVI
coming out of it at this point that is not a thin client.
  _____  


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