[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 #299 from HuangRan <huangran at iscas.ac.cn> ---
Hi Kevin,

(In reply to Kevin Brace from comment #295)
> 
> Hi Frank,
> 
> I am not sure what I can do now.
> You may have to go back further when it comes to going back in the commit,
> and that's all I can say for now.
> I do not really recall which OpenChrome with which commit ID worked with
> Wyse V90LE.
>     As far as I am concerned, the compiled device driver is working with
> several of the test platforms I have.
> Otherwise, I will not do a commit in the first place.
> That being said, for the current master brach head (Commit ID
> d6a65df0e31657495fbdd488c06780b8b33fdccc), the code is now running through
> the LVDS based flat panel detection code, and unfortunately, the previous
> developers were doing some kind of a weird backdoor opeation to figure out
> ("guess" is a better term) what the flat panel native screen resolution is
> if the flat panel does not support I2C bus.
> Unfortunately, this causes problems with those that do not have a flat panel.
> After studying VIA Technologies written frame buffer device driver code over
> the past few days, I found a way to deal with this situation, and in fact,
> OpenChrome already had the code to support this.
> But for some reason, the previous developers were not really using this, so
> I got rid of that weird backdoor code that tries to "guess" the flat panel
> native screen resolution, and now the flat panels without I2C bus can be
> detected properly.
> However, one problem remains, and the problem is, I need a reliable way to
> figure out if a flat panel is connected in the first place, and if a flat
> panel is not connected, the code should not bother trying to figure out the
> flat panel native screen resolution.
> I2C bus cannot be used for this purpose since some flat panels do not
> support I2C bus in the first place.

That's true. for LVDS, sometimes, there is no I2C bus. So there is no need for
EDID probe. The resolution information sometimes is in BIOS(vBIOS table). So
the graphics driver just need try to get that from BIOS and do the mode
setting.
I have not gotten such a board which has the LVDS interface to try.
By the way, in next few days, I will spend some time on current HDMI issue for
KMS driver. Stay tuned...

Thanks,
Frank

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