diff --git a/Documentation/DocBook/writing-an-alsa-driver.tmpl b/Documentation/DocBook/writing-an-alsa-driver.tmpl
index c0781bb1f9b5..c564faab981c 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 {
Example of Hardware Constraints for Channels
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 {
- 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 of Hardware Constraints for Channels
+ Example of Hardware Constraints for Formats
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;
}