On Tue, Feb 18, 2014 at 01:58:22PM +0000, Lin, Mengdong wrote:
Sorry to pick up this thread after a long time.
-----Original Message----- From: daniel.vetter@ffwll.ch [mailto:daniel.vetter@ffwll.ch] On Behalf Of Daniel Vetter Sent: Thursday, January 23, 2014 4:27 PM To: Takashi Iwai
On Thu, Jan 23, 2014 at 8:57 AM, Takashi Iwai tiwai@suse.de wrote:
Thanks for clarification! Maybe we can add output info (eg. display port number) to the eld entries
under /proc/asound/cardx. Is it okay?
It's possible, but the proc file is just a help. It can't be the API. For accessing the information, we'll need some new API, or let inform via sysfs of the new device.
Links in sysfs sound like the best approach. drm already has nodes for each connector, so on the gfx side there's a natural endpoint already. sysfs links also avoids any naming issues from the start, e.g. the above DP connector id might lead to clashes with multiple cards.
Hi Daniel,
Is there a 1:1 mapping between these connector nodes and ports of Gfx display engine? Eg. For Haswell Ultrabook, under /sys/devices/pci0000:00/0000:00:02.0/drm/card0/ There are four connector nodes, card0-DP-1 -> DDI port B card0-eDP-1/ -> DDI port A card0-HDMI-A-1/ -> DDI Port C card0-HDMI-A-2/ -> Which DDI port ? Haswell-ULT does not support port D, and I think port E is for VGA.
There's no fixed mapping with the port and the connector name. The number in the connector name is basically just a running number per connector type. However I do believe we do register the connectors in the order of the ports more or less always, so you can *sometimes* deduce the port name from the connector.
I suppose in this example HDMI-A-1 is port B, HDMI-A-2 is port C, and DP-1 can be either port B or port C. DP++ is the reason why we have overlapping DP and HDMI connectors for the same port.
Hi Takashi,
To make user space figure out which audio output is connected to which screen (connector), maybe we can define a new ALSA control for each HDMI/DP PCM device: e.g. numid=x,iface=PCM,name='Screen',device=3 Reading the control will return the name of the DRM connector nodes like ' card0-DP-1'. The audio driver can get the connector name from the gfx driver.
For DP1.2 Multi-stream transport, it's not supported by i915 and HD-A driver now. But probably there will be sub-nodes for the DP connector node in the future and an index in their name can be used distinguish monitors connected to the same DP port, like card0-DP-1.1, card0-DP-1.2, card0-DP-1.3 ... These names can be used by the above ALSA PCM 'Screen' control, so we can still know which audio output is to which monitor.
Thanks Mengdong
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