[Bug 40252] No udev event for disconnecting VGA/HDMI cable

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=40252

--- Comment #5 from Alex Deucher <agd5f at yahoo.com> 2011-09-22 13:54:02 PDT ---
(In reply to comment #4)
> Mh okay, I my observations were related to HDMI (not VGA).
> Is there a way to find out if a "HPD pin [is] assigned to the
> digital display connector"?

Make sure your have the rlc firmware loaded as it's required for the interrupt
controller to work.

Check your dmesg.  It should show something like:
[drm] Connector 1:
[drm]   HDMI-A
[drm]   HPD2
[drm]   DDC: 0x6440 0x6440 0x6444 0x6444 0x6448 0x6448 0x644c 0x644c
[drm]   Encoders:
[drm]     DFP1: INTERNAL_UNIPHY

In this case HPD2 has been (in theory) wired to the hdmi port.  Plug/unplug in
your hdmi port and check if bit 1 of any of the DC_HPDx_INT_STATUS regs changes
when you connect/disconnect the monitor.

#define DC_HPD1_INT_STATUS                                0x7d00
#define DC_HPD2_INT_STATUS                                0x7d0c
#define DC_HPD3_INT_STATUS                                0x7d18
#define DC_HPD4_INT_STATUS                                0x7d24
#define DC_HPD5_INT_STATUS                                0x7dc0
#define DC_HPD6_INT_STATUS                                0x7df4

You can use radeonreg:
http://cgit.freedesktop.org/~airlied/radeontool/
to dump registers.  E.g. (as root),
./radeonreg regmatch 0x7d00

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