Re: Cubox-i framebuffer support
On 6/28/2014 6:04 PM, Vagrant Cascadian wrote:
> On Sat, Jun 28, 2014 at 07:22:36PM +0200, Rainer Dorsch wrote:
>> you updated https://wiki.debian.org/ArmHardFloatPort/CuBox-i with
>>
>> "The 3.15.1-1~exp1+ kernel in experimental also includes support for
>> framebuffer video over HDMI."
> ...
>> and get console output on HDMI. It is not entirely aligned, i.e. at least on
>> the left and bottom part of the screen a few colums and rows are missing.
>
> It's highly dependent on your HDMI display. Some TVs force overscanning, some
> allow you to change it, and in some the UI to change it is inscrutible. I'd
> hope actual HDMI monitors work fine in general, but haven't actually tried
> any.
>
>
Yes, and the EDIDs the displays send to the source (computer, in this
case) have all the information required for the source to provide the
correct signal.
This should allow the computer to create default settings for that
monitor; these settings should not be overridden unless you know
*exactly* what you're doing. And knowing what you're doing means
interpreting the EDIDs and selecting the appropriate mode.
Otherwise, chances are 99.99+% you'll screw it up more than you'll help it.
<snip>
> Using the default settings works with the one TV I've tested. I could explore
> testing another. Though, it only gets 1024x768@16, which some people might not
> even consider useable.
>
This goes back to the EDIDs being sent. The computer will source
multiple resolutions, scan frequencies and color depths. The display
will handle multiple resolutions, scan frequencies and color depths,
etc. Once the computer gets the EDIDs from the display, it selects the
best combination supported by both. This is generally the highest
resolution common to both, but scan rate and color depth must also be
considered.
> The default monitor configuration may not work with the monitor you're using,
> the framebuffer settings, or a number of other factors.
>
They should work, no matter what the display, due to the EDIDs.
However, the configuration may not be the one you want. Changing either
the monitor or the display adapter can change monitor configurations.
>
>> rd@bokocube:/var/log$ dmesg |grep hdmi
>> [ 0.000000] Kernel command line: root=/dev/mmcblk0p2 rootfstype=ext4 ro
>> rootwait console=ttymxc0,115200 video=mxcfb0:dev=hdmi,1920x1080M@60,if=RGB24
>> cma=64 console=tty1 ahci_imx.hotplug=1
>
> I used a much simpler commandline:
>
> [ 0.000000] Kernel command line: root=/dev/mmcblk0p1 console=ttymxc0,115200
>
> So rather than focing a resolution, color depth, etc. I left it to autodetect
> them. In general, I wouldn't recommend forcing settings unless the defaults
> don't work for you.
>
>
> live well,
> vagrant
>
Definitely (see my comments above).
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