Re: non-PCI driver name lookup

[maya%netbsd.org@localhost]

On Tue, Jul 09, 2019 at 11:07:37AM +0100, Robert Swindells wrote:
> 
> maya%netbsd.org@localhost wrote:
> >On Sun, Jul 07, 2019 at 11:23:14PM +0100, Robert Swindells wrote:
> >> 
> >> The pinebook uses the modesetting X11 driver.
> >> 
> >> An application that calls DRI2Connect() doesn't get back valid values
> >> for device name and driver name so typically assumes that DRI2 isn't
> >> available.
> >> 
> >> This looks to be down to how libdrm tries to work out which driver is
> >> being used from an open file descriptor. I presume the NetBSD specific
> >> code in it does work for PCI devices but it looks like we need to add
> >> something for display devices that are built into the CPU.
> > 
> >I assume, although I can't find proof that it's the case, that you want
> >to adjust the 'unique' value.
> >
> >arm/nvidia/tegra_nouveau.c
> >257:	master->unique = kmem_asprintf("platform:tegra_nouveau:%02d", id);
> 
> The 'unique' value ought to be fine, there is code in
> arm/sunxi/sunxi_drm.c to create it, but it never gets called.
> 
> >I think the code in libdrm looks at this value via DRM_IOCTL_GET_UNIQUE,
> >but I'm not sure.
> 
> It does, and creation of the unique value should be done lazily from
> the DRM_IOCTL_SET_VERSION ioctl. This ioctl fails as the is_master
> member of the file struct for the drm device isn't set. Not got any
> further in tracking down why.
> 
> 

You might find the description here useful,
https://github.com/coypoop/drm/blob/maya-drm51/sys/external/bsd/drm2/dist/drm/drm_ioctl.c#L79-L99