[Pkg-libvirt-maintainers] Bug#1094489: Bug#1094489: libvirt-daemon-driver-qemu: request to add support for Braille display and SDL

[Andrea Bolognani]

Control: tags -1 upstream

On Tue, Jan 28, 2025 at 09:52:08AM -0600, Adam Myrow wrote:
> Package: libvirt-daemon-driver-qemu
> Version: 9.0.0-4+deb12u2
> Severity: wishlist
> 
> Dear Maintainer,
> 
>    * What led up to the situation?
> I am blind, and have a Braille display.  I would like to be able to use the
> Qemu feature where I can pass the Braille display to the guest.  With a
> plain Qemu instance, this can be done by specifying "-display sdl" and
> "-usbdevice braille" as options.  The SDL display apparently is the only
> one that works with the Braille device.  Without this capability, I have to
> use USB passthrough, and must stop Brltty in order to get the display to
> work in the guest.  This is irritating, as I then lose Braille in the host
> OS.  When Qemu is using the "-usbdevice braille" option, the Braille
> display works seemlessly between the host OS and the guest OS.  This
> feature is the main reason I want to use Qemu, and I like the libvirt
> interface, as it makes configuring a guest far easier than writing complex
> scripts to get the exact right command line.
>    * What exactly did you do (or not do) that was effective (or
>      ineffective)?
> Because the Braille device is not directly supported, I used the procedure
> to add custom arguments to the Qemu command line.  I changed the top of the
> XML file so that it begins as follows.
> <domain type='kvm' xmlns:qemu='http://libvirt.org/schemas/domain/qemu/1.0'>
> I then added the following to the end of the XML file for the domain.
>   <qemu:commandline>
>     <qemu:arg value='-usbdevice'/>
>     <qemu:arg value='braille'/>
>   </qemu:commandline>
> I then verified that the guest could see the display.  It did, and is
> communicating with it.  However, because it requires SDL to share the
> display between the host and guest, no text appears.  So, I next changed
> the display to sdl as follows.
>     <graphics type='sdl' display=':0' xauth='/home/myrowa/.Xauthority'>
>    * What was the outcome of this action?
> The domain failed to start, giving the rather cryptic error "qemu
> unexpectedly closed the monitor."
>    * What outcome did you expect instead?
> I expected the SDL window to come up, and the Braille display to show the
> text from the guest OS.

Hi Adam,

having libvirt expose this QEMU feature sounds like a reasonable
idea, however it's something that we can achieve from the Debian
side alone.

Can you please file an upstream issue at

  https://gitlab.com/libvirt/libvirt/-/issues/

so that they're aware of your request and can consider implementing
it?

Thanks.

-- 
Andrea Bolognani <eof at kiyuko.org>
Resistance is futile, you will be garbage collected.
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