Вот вывод dmesg | grep radeon:
[ 16.958136] [drm] radeon defaulting to kernel modesetting.
[ 16.958140] [drm] radeon kernel modesetting enabled.
[ 16.959918] radeon 0000:01:00.0: VRAM: 1024M 0x0000000000000000 - 0x000000003FFFFFFF (1024M used)
[ 16.959921] radeon 0000:01:00.0: GTT: 512M 0x0000000040000000 - 0x000000005FFFFFFF
[ 16.963391] [drm] radeon: 1024M of VRAM memory ready
[ 16.963393] [drm] radeon: 512M of GTT memory ready.
[ 16.963463] radeon 0000:01:00.0: irq 51 for MSI/MSI-X
[ 16.963474] radeon 0000:01:00.0: radeon: using MSI.
[ 16.963510] [drm] radeon: irq initialized.
[ 17.003034] radeon 0000:01:00.0: WB enabled
[ 17.003038] radeon 0000:01:00.0: fence driver on ring 0 use gpu addr 0x0000000040000c00 and cpu addr 0xffff88009fbb7c00
[ 17.035725] [drm] radeon: power management initialized
[ 18.021251] fbcon: radeondrmfb (fb0) is primary device
[ 18.021497] fb0: radeondrmfb frame buffer device
[ 18.021515] [drm] Initialized radeon 2.18.0 20080528 for 0000:01:00.0 on minor 0
Взял исходники ядра, посмотрел в drivers/gpu/drm/radeon/radeon_pm.c: должно добавится устройтсво с name=radeon и temp1_input, где будет температура сенсора.
Карта ATI Mobility Radeon HD3650, чип RV635, открытый драйвер вполне с ним дружит.