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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>
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1 changed files with 20 additions and 19 deletions
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@ -3250,18 +3250,19 @@ struct _snd_pcm_runtime {
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<title>Example of Hardware Constraints for Channels</title>
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<programlisting>
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<![CDATA[
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static int hw_rule_format_by_channels(struct snd_pcm_hw_params *params,
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static int hw_rule_channels_by_format(struct snd_pcm_hw_params *params,
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struct snd_pcm_hw_rule *rule)
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{
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struct snd_interval *c = hw_param_interval(params,
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SNDRV_PCM_HW_PARAM_CHANNELS);
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SNDRV_PCM_HW_PARAM_CHANNELS);
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struct snd_mask *f = hw_param_mask(params, SNDRV_PCM_HW_PARAM_FORMAT);
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struct snd_mask fmt;
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struct snd_interval ch;
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snd_mask_any(&fmt); /* Init the struct */
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if (c->min < 2) {
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fmt.bits[0] &= SNDRV_PCM_FMTBIT_S16_LE;
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return snd_mask_refine(f, &fmt);
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snd_interval_any(&ch);
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if (f->bits[0] == SNDRV_PCM_FMTBIT_S16_LE) {
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ch.min = ch.max = 1;
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ch.integer = 1;
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return snd_interval_refine(c, &ch);
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}
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return 0;
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}
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@ -3285,27 +3286,27 @@ struct _snd_pcm_runtime {
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</para>
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<para>
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The rule function is called when an application sets the number of
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channels. But an application can set the format before the number of
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channels. Thus you also need to define the inverse rule:
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The rule function is called when an application sets the PCM
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format, and it refines the number of channels accordingly.
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But an application may set the number of channels before
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setting the format. Thus you also need to define the inverse rule:
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<example>
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<title>Example of Hardware Constraints for Channels</title>
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<title>Example of Hardware Constraints for Formats</title>
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<programlisting>
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<![CDATA[
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static int hw_rule_channels_by_format(struct snd_pcm_hw_params *params,
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static int hw_rule_format_by_channels(struct snd_pcm_hw_params *params,
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struct snd_pcm_hw_rule *rule)
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{
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struct snd_interval *c = hw_param_interval(params,
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SNDRV_PCM_HW_PARAM_CHANNELS);
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SNDRV_PCM_HW_PARAM_CHANNELS);
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struct snd_mask *f = hw_param_mask(params, SNDRV_PCM_HW_PARAM_FORMAT);
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struct snd_interval ch;
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struct snd_mask fmt;
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snd_interval_any(&ch);
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if (f->bits[0] == SNDRV_PCM_FMTBIT_S16_LE) {
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ch.min = ch.max = 1;
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ch.integer = 1;
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return snd_interval_refine(c, &ch);
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snd_mask_any(&fmt); /* Init the struct */
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if (c->min < 2) {
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fmt.bits[0] &= SNDRV_PCM_FMTBIT_S16_LE;
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return snd_mask_refine(f, &fmt);
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}
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return 0;
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}
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