ALSA: hda - Update documentation

Update documentation regarding codec probing; the new probe_only option
and the new probe_mask usage.
Signed-off-by: Takashi Iwai <tiwai@suse.de>

Documentation/sound/alsa/ALSA-Configuration.txt

@@ -757,6 +757,9 @@ Prior to version 0.9.0rc4 options had a 'snd_' prefix. This was removed.
     model	- force the model name
     position_fix - Fix DMA pointer (0 = auto, 1 = use LPIB, 2 = POSBUF)
     probe_mask  - Bitmask to probe codecs (default = -1, meaning all slots)
+    		  When the bit 8 (0x100) is set, the lower 8 bits are used
+		  as the "fixed" codec slots; i.e. the driver probes the
+		  slots regardless what hardware reports back
     probe_only	- Only probing and no codec initialization (default=off);
 		  Useful to check the initial codec status for debugging
     bdl_pos_adj	- Specifies the DMA IRQ timing delay in samples.

Documentation/sound/alsa/HD-Audio.txt

@@ -109,6 +109,13 @@ slot, pass `probe_mask=1`.  For the first and the third slots, pass
 Since 2.6.29 kernel, the driver has a more robust probing method, so
 this error might happen rarely, though.
 
+On a machine with a broken BIOS, sometimes you need to force the
+driver to probe the codec slots the hardware doesn't report for use.
+In such a case, turn the bit 8 (0x100) of `probe_mask` option on.
+Then the rest 8 bits are passed as the codec slots to probe
+unconditionally.  For example, `probe_mask=0x103` will force to probe
+the codec slots 0 and 1 no matter what the hardware reports.
+
 
 Interrupt Handling
 ~~~~~~~~~~~~~~~~~~
@@ -461,6 +468,16 @@ run with `--no-upload` option, and attach the generated file.
 There are some other useful options.  See `--help` option output for
 details.
 
+When a probe error occurs or when the driver obviously assigns a
+mismatched model, it'd be helpful to load the driver with
+`probe_only=1` option (at best after the cold reboot) and run
+alsa-info at this state.  With this option, the driver won't configure
+the mixer and PCM but just tries to probe the codec slot.  After
+probing, the proc file is available, so you can get the raw codec
+information before modified by the driver.  Of course, the driver
+isn't usable with `probe_only=1`.  But you can continue the
+configuration via hwdep sysfs file if hda-reconfig option is enabled.
+
 
 hda-verb
 ~~~~~~~~