[Libdlo] udlfb moving from staging to fbdev/mainline

Bernie Thompson bernie at plugable.com
Sun Jan 23 21:55:27 PST 2011

Hi Alexander,

Sorry for the delay.  Some quick answers.

On Fri, Jan 14, 2011 at 1:28 PM, Alexander Todorov <atodorov at otb.bg> wrote:
> 1) What happens to git.plugable.com? Which is now the upstream source of
> udlfb?

The fbdev tree of the kernel (currently maintained by Paul Mundt)
should be the primary upstream source. That is, patches should be
submitted there first. Feel free to copy me as a udlfb maintainer --
I should be able to give patches testing on a variety of DisplayLink

http://git.plugable.com/ has been useful during this interim period --
for compiling loadable modules that work back to much older kernels,
and I'll try to keep it going in that role for a little while longer
-- but as the user base moves onto newer kernels, it shouldn't be
needed and will be retired in favor of the version directly in the
kernel tree.

And the primary documentation that will be best maintained for udlfb
is in the kernel itself:

> 2) What happens to libdlo mailing list? If udlfb goes under the belt of
> fbdev should discussions be moved to fbdev list and udlfb abandoned?

Yes, I believe development discussions should move to
http://vger.kernel.org/vger-lists.html#linux-fbdev -- it is where
patches should be submitted, there is a critical mass of development
expertise already on that list, and adding udlfb to the mix will be
good for raising the profile of DisplayLink and other USB graphics on
Linux.  By moving the discusses there, I'm hopeful faster progress
will be made.  We've been able to have focused DisplayLink discussions
here, but they've also suffered from a lack of the right involvement.

That said, linux-fbdev isn't the right place for DisplayLink Linux
end-user discussions (linux-fbdev is very developer/patch focused), so
I assume this libdlo list will remain the best place for users helping
other users.

> 3) I haven't been following fbdev development closely. Are there any
> exciting new features that we can expect in the future? Can you share if you
> know.

The driver is fairly stable and functional in 2.6.38-rc2 and on
git.plugable.com.  The difficult problems have moved mostly to the
higher-level xorg configuration area.

In terms of work remaining, there are 2-3 udlfb patches floating
around the lists (e.g. Andrew's patches for composite devices) that
need to get submitted to linux-fbdev.  The remaining udlfb todos I'd
like to see are:

1) Successful proposal of a damage ioctl/interface for fbdev, so the
standard fbdev X server, etc. will work on DisplayLink devices, and
we'll no longer need a DisplayLink specific X server
2) Pseudo-24 or 32 bpp support, so Xinerama users don't have to set
their main display to 16bpp
3) Add a "persistent" mode to udlfb, where the virtual USB
framebuffer, once created, persists even after the USB device
disconnects. When a USB device reconnects, we first try to match it up
to it's existing virtual framebuffer before creating a new one. This
would be towards the goal of having X keep working through a USB
unplug/replug event. The groundwork for this is already in udlfb.

Are there other features on anyone else's wishlist?


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