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ALSA: doc: Recommend the use of snd_ctl_elem_info()

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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>
This commit is contained in:
Takashi Iwai 2014-10-20 18:06:04 +02:00
parent f114040e3e
commit be93709cb1
1 changed files with 23 additions and 0 deletions
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23
Documentation/DocBook/writing-an-alsa-driver.tmpl
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@ -3657,6 +3657,29 @@ struct _snd_pcm_runtime {
</informalexample> </informalexample>
</para> </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> <para>
Some common info callbacks are available for your convenience: Some common info callbacks are available for your convenience:
<function>snd_ctl_boolean_mono_info()</function> and <function>snd_ctl_boolean_mono_info()</function> and