No output on display with Weston using fbdev backend

nsolanki at nsolanki at
Wed Mar 21 14:12:41 UTC 2018

On 2018-03-21 14:52, Pekka Paalanen wrote:
> On Wed, 21 Mar 2018 14:40:13 +0530
> nsolanki at wrote:
>> Hi Wayland Team,
>> I am using weston 1.9.0-r0 version and compiled weston for fbdev
>> backend.
>> But I do not see any output on display. Basically I do not see call
>> reaching to "ioctl(fd, FBIOPUT_VSCREENINFO, &varinfo)" in function
>> fbdev_set_screen_info().
>> So, if I add a call "ioctl(fd,  FBIOPUT_VSCREENINFO, &varinfo)" in
>> function fbdev_output_repaint_pixman(), I can see output on display.
>> Should I add FBIOPUT_VSCREENINFO ioctl in function
>> fbdev_output_repaint_pixman() ?
>> Can you please help me regarding this?
> Hi,
> it is unlikely to find help with such an old Weston, even more so with
> the fbdev backend which at least I would like to just delete already.
> But the fbdev backend is still in Weston, so I'd recommend trying a
> more recent version. You can also check git to see if there are code
> changes in the fbdev-backend.
> I don't think FBIOPUT_VSCREENINFO at every repaint is good in any case.
> You might be interested in reviewing this patch or the whole series:
> What I've occasionally tested the fbdev-backend, I've never needed a
> call to FBIOPUT_VSCREENINFO, so your use case must be somehow
> different. Explaining exactly how and in what kind of a system and
> environment you are running Weston could help. E.g. is it a secondary
> fbdev device, or using UDL driver.
> Thanks,
> pq


In our FB driver FBIOPUT_VSCREENINFO internally calls a commit() call, 
which actually displays content on panel.
So, it is needed it seems. I am not sure how drawing in mmap() ed memory 
by opening /dev/fb0 can display content on panel without a commit() call 
as weston is currently doing.


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