alsa-mixer: autodetect the ELD device

This removes the need to hardcode the ELD device index in the path
configuration. The hardcoded values don't work with the Intel HDMI LPE
driver.

BugLink: https://bugs.freedesktop.org/show_bug.cgi?id=100488

src/modules/alsa/mixer/paths/analog-output.conf.common

@@ -64,8 +64,12 @@
 ; mute-during-activation = yes | no      # If this path supports hardware mute, should the hw mute be used while activating this
 ;                                        # path? In some cases this can reduce extra noises during port switching, while in other
 ;                                        # cases this can increase such noises. Default: no.
-; eld-device = ...                       # If this is an HDMI port, here's where to specify the device number for the ELD mixer
-;                                        # control. The default is to not make use of ELD information.
+; eld-device = ...                       # If this is an HDMI port, set to "auto" so that PulseAudio will try to read
+;                                        # the monitor ELD information from the ALSA mixer. By default the ELD information
+;                                        # is not read, because it's only applicable with HDMI. Earlier the "auto" option
+;                                        # didn't exist, and the hw device index had to be manually configured. For
+;                                        # backwards compatibility, it's still possible to manually configure the device
+;                                        # index using this option.
 ;
 ; [Properties]                           # Property list for this path. The list is merged into the port property list.
 ; <key> = <value>                        # Each property is defined on its own line.

src/modules/alsa/mixer/paths/hdmi-output-0.conf

@@ -1,7 +1,7 @@
 [General]
 description = HDMI / DisplayPort
 priority = 59
-eld-device = 3
+eld-device = auto
 
 [Properties]
 device.icon_name = video-display

src/modules/alsa/mixer/paths/hdmi-output-1.conf

@@ -1,7 +1,7 @@
 [General]
 description = HDMI / DisplayPort 2
 priority = 58
-eld-device = 7
+eld-device = auto
 
 [Properties]
 device.icon_name = video-display

src/modules/alsa/mixer/paths/hdmi-output-2.conf

@@ -1,7 +1,7 @@
 [General]
 description = HDMI / DisplayPort 3
 priority = 57
-eld-device = 8
+eld-device = auto
 
 [Properties]
 device.icon_name = video-display

src/modules/alsa/mixer/paths/hdmi-output-3.conf

@@ -1,7 +1,7 @@
 [General]
 description = HDMI / DisplayPort 4
 priority = 56
-eld-device = 9
+eld-device = auto
 
 [Properties]
 device.icon_name = video-display

src/modules/alsa/mixer/paths/hdmi-output-4.conf

@@ -1,7 +1,7 @@
 [General]
 description = HDMI / DisplayPort 5
 priority = 55
-eld-device = 10
+eld-device = auto
 
 [Properties]
 device.icon_name = video-display

src/modules/alsa/mixer/paths/hdmi-output-5.conf

@@ -1,7 +1,7 @@
 [General]
 description = HDMI / DisplayPort 6
 priority = 54
-eld-device = 11
+eld-device = auto
 
 [Properties]
 device.icon_name = video-display

src/modules/alsa/mixer/paths/hdmi-output-6.conf

@@ -1,7 +1,7 @@
 [General]
 description = HDMI / DisplayPort 7
 priority = 53
-eld-device = 12
+eld-device = auto
 
 [Properties]
 device.icon_name = video-display

src/modules/alsa/mixer/paths/hdmi-output-7.conf

@@ -1,7 +1,7 @@
 [General]
 description = HDMI / DisplayPort 8
 priority = 52
-eld-device = 13
+eld-device = auto
 
 [Properties]
 device.icon_name = video-display