Created attachment 18361 [details] [review]
Patch to libdrm to fix the problem on FreeBSD/amd64

FreeBSD amd64 reports a sign-extension on the ioctl calls which pass through drmIoctl in xf86drm.c. The problem is that the request is typed as "int" (a signed, 32-bit type), while the ioctl system call expects this to be an "unsigned long" (an unsigned, 64-bit type). As it first performs the signed conversion, then the field extension, any ioctl's with the high-bit set will have all high 32-bits set in the ioctl passed to the driver. The drm driver is only looking for unsigned long ioctl requests, so none of these high ioctls will succeed. This eventually leads to a hang in the X-server on my system.

For instance: ioctl request 0xc0001432 becomes 0xffffffffc0001432, but the drm driver is looking for 0x00000000c0001432, so the subsequent ioctls never succeed.