[PATCH] fbdev: Add an fbdev compositor backend using pixman and evdev

[Nerdopolis]

Nerdopolis <bluescreen_avenger at ...> writes:


> I see.
> The only concern is that can the vesafb fbdev device resolution be changed in
> runtime if its too small?
> Otherwise users are going to have to manually set the framebuffer size by
> correcting the correct vga= argument with grub if they get the wrong size.
>
... 
> 
> I think that would mean there is an issue with Ubuntu, (I would assume it's
> Casper as it runs and configures the live environment during runtime). 
> And that this would need to be fixed in order for fbdev-backended Weston to
> work on VirtualBox.
> 
> I tested it on a default Kubuntu 12.10 Live ISO, and when it booted, 
> there was no /dev/fb0 as well.
> 
> As this is an issue within a distribution, either a workaround will have to be
> provided, or we'll have to wait for the distribution to fix this issue.
> 
> I don't know enough about what could be causing the issue that the same ISO
> when booted as a Live CD does not have /dev/fb0, but when its installed 
> it has /dev/fb0.
> 
To answer my own questions after more research, it seems that the ability 
to change the resolution depends on the framebuffer driver.
It seems that vesafb can not change the resolution without a reboot, however
a driver called uvesafb can. It seems though that although some distros
provide it by default, they might not include the userspace 'v86d' program 
by default that uvesafb requires. (I tested on Ubuntu)


In order to use uvesafb:
modprobe uvesafb mode_option=1024x768-32

and from there the mode can be set again by echoing one of the modes listed in
/sys/devices/platform/uvesafb.0/graphics/fb0/modes  into
/sys/devices/platform/uvesafb.0/graphics/fb0/mode

...So in the case that a system doesn't create an fbdev by default, and the user
is using the framebuffer backend, could weston-launch possibly do this