Re: [PATCH 4/5] drm/vgem: getparam ioctl

[Adam Jackson <ajax@redhat.com>]

On 2/8/12 6:19 PM, Ben Widawsky wrote:
> Similar to i915, it's nice to be able to query this device uniquely and
> get some info
>
> Signed-off-by: Ben Widawsky<ben@bwidawsk.net>

So, this is actually not especially useful as written.  You'd like to be 
able to use this to find the vgem device node, but since it's a 
device-specific ioctl it collides with whatever happens to be 
device-specific ioctl number 2 on whatever device you've opened.  On 
i915, that's I915_FLIP, and you promptly oops the machine.

Comedy. Gold.

Which is fine, really.  The way I was anticipating finding the vgem node 
was to just scrape the device node name out of 
/sys/bus/platform/devices/vgem/cardN, because why do anything O(n) when 
you could do it O(1).  I guess that doesn't help OSes that aren't Linux, 
and I guess if pressed to care about that I'd say hang it off drm_getcap.

- ajax