ALSA: doc: Recommend the use of snd_ctl_elem_info()
Instead of the open code for the info call back of enum elements,
recommend the use of snd_ctl_elem_info(), which will reduce lots of
codes.
Signed-off-by: Takashi Iwai <tiwai@suse.de>
diff --git a/Documentation/DocBook/writing-an-alsa-driver.tmpl b/Documentation/DocBook/writing-an-alsa-driver.tmpl
index 784793d..84ef6a9 100644
--- a/Documentation/DocBook/writing-an-alsa-driver.tmpl
+++ b/Documentation/DocBook/writing-an-alsa-driver.tmpl
@@ -3658,6 +3658,29 @@
</para>
<para>
+ The above callback can be simplified with a helper function,
+ <function>snd_ctl_enum_info</function>. The final code
+ looks like below.
+ (You can pass ARRAY_SIZE(texts) instead of 4 in the third
+ argument; it's a matter of taste.)
+
+ <informalexample>
+ <programlisting>
+<![CDATA[
+ static int snd_myctl_enum_info(struct snd_kcontrol *kcontrol,
+ struct snd_ctl_elem_info *uinfo)
+ {
+ static char *texts[4] = {
+ "First", "Second", "Third", "Fourth"
+ };
+ return snd_ctl_enum_info(uinfo, 1, 4, texts);
+ }
+]]>
+ </programlisting>
+ </informalexample>
+ </para>
+
+ <para>
Some common info callbacks are available for your convenience:
<function>snd_ctl_boolean_mono_info()</function> and
<function>snd_ctl_boolean_stereo_info()</function>.