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 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. _______________________________________________ dri-devel mailing list dri-devel@xxxxxxxxxxxxxxxxxxxxx https://lists.freedesktop.org/mailman/listinfo/dri-devel
