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Commit be93709c authored by Takashi Iwai's avatar Takashi Iwai
Browse files

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: default avatarTakashi Iwai <tiwai@suse.de>
parent f114040e

Documentation/DocBook/writing-an-alsa-driver.tmpl

+23 −0
Original line number Diff line number Diff line
@@ -3657,6 +3657,29 @@ struct _snd_pcm_runtime { 
          </informalexample>

        </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