Comment 61 for bug 542660

This is still an issue. I tried (kubuntu) natty-desktop-amd64+mac.iso from 2011-01-03 on a 27 inch iMac with Radeon 4850 (iMac11,1). Unfortunately, i have no external LCD, so i can't help you with the output of /sys/class/drm/card0.
However, i did boot the livecd with vesa graphics, and this is the contents of /sys/class/drm/card0 after loading the radeon driver manually (dmidecode attached above);

root@ubuntu:/sys/class/drm/card0# ls
dev device power subsystem uevent

root@ubuntu:/sys/class/drm/card0# find -L . -maxdepth 2 -type f -print -execdir cat {} \;
./uevent
MAJOR=226
MINOR=0
DEVNAME=dri/card0
DEVTYPE=drm_minor
./dev
226:0
./subsystem/version
drm 1.1.0 20060810
find: File system loop detected; `./subsystem/card0' is part of the same file system loop as `.'.
./device/uevent
PCI_CLASS=30000
PCI_ID=1002:944A
PCI_SUBSYS_ID=106B:00B5
PCI_SLOT_NAME=0000:01:00.0
MODALIAS=pci:v00001002d0000944Asv0000106Bsd000000B5bc03sc00i00
./device/resource
0x00000000c0000000 0x00000000cfffffff 0x000000000014220c
0x0000000000000000 0x0000000000000000 0x0000000000000000
0x00000000d0620000 0x00000000d062ffff 0x0000000000140204
0x0000000000000000 0x0000000000000000 0x0000000000000000
0x0000000000002000 0x00000000000020ff 0x0000000000040101
0x0000000000000000 0x0000000000000000 0x0000000000000000
0x00000000d0600000 0x00000000d061ffff 0x000000000004e202
0x0000000000000000 0x0000000000000000 0x0000000000000000
0x0000000000000000 0x0000000000000000 0x0000000000000000
0x0000000000000000 0x0000000000000000 0x0000000000000000
0x0000000000000000 0x0000000000000000 0x0000000000000000
0x0000000000000000 0x0000000000000000 0x0000000000000000
0x0000000000000000 0x0000000000000000 0x0000000000000000
./device/vendor
0x1002
./device/device
0x944a
./device/subsystem_vendor
0x106b
./device/subsystem_device
0x00b5
./device/class
0x030000
./device/irq
16
./device/local_cpus
00000000,0000000f
./device/local_cpulist
0-3
./device/modalias
pci:v00001002d0000944Asv0000106Bsd000000B5bc03sc00i00
./device/numa_node
-1
./device/dma_mask_bits
32
./device/consistent_dma_mask_bits
32
./device/enable
1
./device/broken_parity_status
0
./device/msi_bus
./device/remove
cat: ././device/remove: Permission denied
./device/rescan
cat: ././device/rescan: Permission denied
./device/config
J�@�
    �b� k�`�P
@� k�X���
  ��./device/resource0
cat: ././device/resource0: Input/output error
./device/resource0_wc
cat: ././device/resource0_wc: Input/output error
./device/resource2
cat: ././device/resource2: Input/output error
./device/resource4
cat: ././device/resource4: Invalid argument
./device/rom
cat: ././device/rom: Invalid argument
./device/boot_vga
1
./device/reset
cat: ././device/reset: Permission denied
./power/wakeup

./power/wakeup_count

./power/wakeup_active_count

./power/wakeup_hit_count

./power/wakeup_active

./power/wakeup_total_time_ms

./power/wakeup_max_time_ms

./power/wakeup_last_time_ms

./power/runtime_status
unsupported
./power/control
auto
./power/runtime_suspended_time
0
./power/runtime_active_time
0
./power/autosuspend_delay_ms
cat: ././power/autosuspend_delay_ms: Input/output error