Re: [Qemu-devel] Linux framebuffer emulation in qemu linux-user

[Ilyes Gouta]

On Thu, Sep 9, 2010 at 11:57 PM, Alexander Graf <address@hidden> wrote:

On 09.09.2010, at 23:06, Ilyes Gouta wrote:

>
>
> On Thu, Sep 9, 2010 at 9:39 PM, Ilyes Gouta <address@hidden> wrote:
> Hi,
>
> Well, actually I'd like to run sh4 binaries in linux-user mode, where these are actually DirectFB applications which rely on the standard Linux framebuffer to display things.
>
> In my use case, I'd like to route these ioctl in qemu to be handled by the SDL back-end (or even a DirectFB instance running on the host) instead of being dispatched to the native framebuffer driver, running on the host.
>
> Is this feature available in the current qemu code base?

Please don't top post.

It is not available in qemu and doesn't belong there. Qemu's linux-user target really only passes things through. It shouldn't intercept them and try to be clever. That's the task of the surrounding stack.

For example in your case, I'd write an LD_PRELOAD that would trap open on /dev/fb* and emulates mmap and ioctls to that device. This way you get a generic way of displaying fb contents in windows that might be useful for other use cases too.

Another thing you could look into is cuse. Maybe you could expose /dev/fb0 as a cuse device and trap things through that.

Indeed, it sounds a lot more generic. I already started hacking into qemu to implement (prototype) rerouting the framebuffer ioctls, and it's surprisingly easy :) If cuse's learning curve isn't stiff, I'll consider moving my changes into a separate shared library.

Thanks Alex,

-Ilyes

 

 

Alex