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authorTakashi Iwai <tiwai@suse.de>2013-02-05 12:24:22 +0100
committerTakashi Iwai <tiwai@suse.de>2013-02-05 12:24:22 +0100
commita690a2a1eb32e533e2b2afb1daeef3c4011d47e9 (patch)
treef0c0cdf087f6922448db96cf222122aa443de4b1 /Documentation/DocBook
parent05dc0fc9d01537a66d9a0cffe2e96296d8f4c7ac (diff)
downloadlinux-a690a2a1eb32e533e2b2afb1daeef3c4011d47e9.tar.gz
ALSA: Fix wrong description about hw constraints
The definitions of hw constraint functions are wrongly placed, and the description about the function is also wrong. hw_rule_channels_by_format actually refines the channels depending on the format, not vice versa. Reported-by: Peter Ujfalusi <peter.ujfalusi@ti.com> Signed-off-by: Takashi Iwai <tiwai@suse.de>
Diffstat (limited to 'Documentation/DocBook')
-rw-r--r--Documentation/DocBook/writing-an-alsa-driver.tmpl39
1 files changed, 20 insertions, 19 deletions
diff --git a/Documentation/DocBook/writing-an-alsa-driver.tmpl b/Documentation/DocBook/writing-an-alsa-driver.tmpl
index c0781bb1f9b..c564faab981 100644
--- a/Documentation/DocBook/writing-an-alsa-driver.tmpl
+++ b/Documentation/DocBook/writing-an-alsa-driver.tmpl
@@ -3250,18 +3250,19 @@ struct _snd_pcm_runtime {
<title>Example of Hardware Constraints for Channels</title>
<programlisting>
<![CDATA[
- static int hw_rule_format_by_channels(struct snd_pcm_hw_params *params,
+ static int hw_rule_channels_by_format(struct snd_pcm_hw_params *params,
struct snd_pcm_hw_rule *rule)
{
struct snd_interval *c = hw_param_interval(params,
- SNDRV_PCM_HW_PARAM_CHANNELS);
+ SNDRV_PCM_HW_PARAM_CHANNELS);
struct snd_mask *f = hw_param_mask(params, SNDRV_PCM_HW_PARAM_FORMAT);
- struct snd_mask fmt;
+ struct snd_interval ch;
- snd_mask_any(&fmt); /* Init the struct */
- if (c->min < 2) {
- fmt.bits[0] &= SNDRV_PCM_FMTBIT_S16_LE;
- return snd_mask_refine(f, &fmt);
+ snd_interval_any(&ch);
+ if (f->bits[0] == SNDRV_PCM_FMTBIT_S16_LE) {
+ ch.min = ch.max = 1;
+ ch.integer = 1;
+ return snd_interval_refine(c, &ch);
}
return 0;
}
@@ -3285,27 +3286,27 @@ struct _snd_pcm_runtime {
</para>
<para>
- The rule function is called when an application sets the number of
- channels. But an application can set the format before the number of
- channels. Thus you also need to define the inverse rule:
+ The rule function is called when an application sets the PCM
+ format, and it refines the number of channels accordingly.
+ But an application may set the number of channels before
+ setting the format. Thus you also need to define the inverse rule:
<example>
- <title>Example of Hardware Constraints for Channels</title>
+ <title>Example of Hardware Constraints for Formats</title>
<programlisting>
<![CDATA[
- static int hw_rule_channels_by_format(struct snd_pcm_hw_params *params,
+ static int hw_rule_format_by_channels(struct snd_pcm_hw_params *params,
struct snd_pcm_hw_rule *rule)
{
struct snd_interval *c = hw_param_interval(params,
- SNDRV_PCM_HW_PARAM_CHANNELS);
+ SNDRV_PCM_HW_PARAM_CHANNELS);
struct snd_mask *f = hw_param_mask(params, SNDRV_PCM_HW_PARAM_FORMAT);
- struct snd_interval ch;
+ struct snd_mask fmt;
- snd_interval_any(&ch);
- if (f->bits[0] == SNDRV_PCM_FMTBIT_S16_LE) {
- ch.min = ch.max = 1;
- ch.integer = 1;
- return snd_interval_refine(c, &ch);
+ snd_mask_any(&fmt); /* Init the struct */
+ if (c->min < 2) {
+ fmt.bits[0] &= SNDRV_PCM_FMTBIT_S16_LE;
+ return snd_mask_refine(f, &fmt);
}
return 0;
}