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-rw-r--r--Documentation/sound/alsa/DocBook/writing-an-alsa-driver.tmpl15
1 files changed, 11 insertions, 4 deletions
diff --git a/Documentation/sound/alsa/DocBook/writing-an-alsa-driver.tmpl b/Documentation/sound/alsa/DocBook/writing-an-alsa-driver.tmpl
index db0b7d2dc477..0475478c2484 100644
--- a/Documentation/sound/alsa/DocBook/writing-an-alsa-driver.tmpl
+++ b/Documentation/sound/alsa/DocBook/writing-an-alsa-driver.tmpl
@@ -3422,10 +3422,17 @@ struct _snd_pcm_runtime {
<para>
The <structfield>iface</structfield> field specifies the type of
- the control,
- <constant>SNDRV_CTL_ELEM_IFACE_XXX</constant>. There are
- <constant>MIXER</constant>, <constant>PCM</constant>,
- <constant>CARD</constant>, etc.
+ the control, <constant>SNDRV_CTL_ELEM_IFACE_XXX</constant>, which
+ is usually <constant>MIXER</constant>.
+ Use <constant>CARD</constant> for global controls that are not
+ logically part of the mixer.
+ If the control is closely associated with some specific device on
+ the sound card, use <constant>HWDEP</constant>,
+ <constant>PCM</constant>, <constant>RAWMIDI</constant>,
+ <constant>TIMER</constant>, or <constant>SEQUENCER</constant>, and
+ specify the device number with the
+ <structfield>device</structfield> and
+ <structfield>subdevice</structfield> fields.
</para>
<para>
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