Does anyone have any feedback for me? I'm able to modify libdrm to make things
work for me, but I'm pretty sure that isn't the right thing to do.
________________________________
From: Defnet, Benjamin R
Sent: Monday, October 12, 2009 8:59 PM
To: '[email protected]'
Subject: drmOpenByName opening incorrect minor?
Here is my situation. I have two drm devices "alpha" and "beta" both mapped to
the same hw with the same PCI Bus ID. "alpha" is at minor 0 and "beta" is at
minor 1.
If I do the following:
drmOpen("beta", NULL);
drmOpen("beta", NULL);
The second call will actually return a file descriptor pointing to the "alpha"
device. Based on my code traces, this is because for the second call,
drmOpenByName( ) will iterate through the minors and find "beta" at minor 1,
but the PCI Bus ID will be non-null due to the previous drmOpen, so it will
skip that and not find any other name matches. It will then try the
"Backward-compatiblity /proc support" loop. It will find a match at minor 1,
but will then call drmOpenByBusid( ). drmOpenByBusid( ) will again iterate
through the minors looking for a PCI Bus ID match and will find one at minor 0,
the "alpha" drm device, so it will open that and return the fd.
This obviously isn't what I expected. I expected it to open minor 1, the
"beta" drm device. I end up using the wrong fd and get crashes because my
"alpha" device obviously can't handle the "beta" ioctls.
A few questions:
1) Is this expected behavior?
2) In drmOpenByName( ), why does it reject a match if the PCI Bus ID is
non-null? drmOpenByBusID( ) doesn't do that.
3) Any ideas how I can make this work assuming my setup above (2 drm
devices with same PCI Bus ID) can't change?
Thank you,
Ben
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