On Thu, 28 May 2020 at 10:46, /wrote: > > Simon Ser <contact@xxxxxxxxxxx> 於 2020年5月25日 週一 上午3:25寫道： > > On Sunday, May 24, 2020 8:53 PM, Daniel Vetter <daniel@xxxxxxxx> wrote: > > > On Sat, May 23, 2020 at 5:44 PM Mauro Rossi issor.oruam@xxxxxxxxx wrote: > > > > > > > OpenByFB is introduced to overcome GPU driver loading order issue > > > > on a device with multiple GPUs, e.g. Intel iGPU and Nvidia dGPU > > > > where the first drmfb kernel module loaded will become device file > > > > /dev/dri/card0 and the second will become /dev/dri/card1 > > > > The use case is to prefer Intel iGPU over dGPU, or viceversa, > > > > in a deterministic and reliable manner. > > > > OpenByFB function opens the DRM device with specified fb and node type, > > > > thus enabling gralloc to open the correct device node of the primary fb, > > > > regardless of the GPU driver loading order. > > > > > > The fbdev load ordering is as inconsistent/random as the dri node > > > loading. Well more so, because you might have random firmware fbdev > > > drivers hanging out there. Hence I'm not following how this solves > > > anything for your problem. > > > > > > I think usually what userspace does it look at the boot_vga property > > > of the underlying device in sysfs, and prefer that one. > > Thank you for the reply. > I'm not the expert so > I can't fully understand what you mean. > What does 'boot_vga' mean and how could it help our problem? > The boot_vga is a flag which indicating which VGA (graphics) device the system booted from. > The main problem we're trying to solve is to > find the DRM device of the primary framebuffer (fb0). > I believe /sys/class/graphics/fb0/device/drm > is the correct one we could use. > At least it works on all devices I've tested > including nvidia optimus notebooks. > If there is a simpler way to get the DRM device of fb0 > I'm happy to learn. > > > Yes. See [1] for an example of how to do this. > > > > [1]: https://github.com/swaywm/wlroots/blob/5c942bd5972afee9a68cb15c14aa83b4b0aaf82d/backend/session/session.c#L331 > > Thank you for the example. > However, our target platform is Android and > Android doesn't have udev. So I'm afraid we can't use it. Indeed - udev isn't as wide-spread as it could have been. A quick WIP should be in your inbox. It implements boot_vga support for drmDevice. Do give it some test/love and resubmit once it works on your end. -Emil _______________________________________________ dri-devel mailing list dri-devel@xxxxxxxxxxxxxxxxxxxxx https://lists.freedesktop.org/mailman/listinfo/dri-devel
