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-rw-r--r--Documentation/DocBook/writing-an-alsa-driver.tmpl58
1 files changed, 29 insertions, 29 deletions
diff --git a/Documentation/DocBook/writing-an-alsa-driver.tmpl b/Documentation/DocBook/writing-an-alsa-driver.tmpl
index fb32aead5a0..bd6fee22c4d 100644
--- a/Documentation/DocBook/writing-an-alsa-driver.tmpl
+++ b/Documentation/DocBook/writing-an-alsa-driver.tmpl
@@ -871,9 +871,8 @@
<para>
This function itself doesn't allocate the data space. The data
must be allocated manually beforehand, and its pointer is passed
- as the argument. This pointer is used as the
- (<parameter>chip</parameter> identifier in the above example)
- for the instance.
+ as the argument. This pointer (<parameter>chip</parameter> in the
+ above example) is used as the identifier for the instance.
</para>
<para>
@@ -2304,7 +2303,7 @@ struct _snd_pcm_runtime {
<constant>SNDRV_PCM_INFO_XXX</constant>. Here, at least, you
have to specify whether the mmap is supported and which
interleaved format is supported.
- When the is supported, add the
+ When the hardware supports mmap, add the
<constant>SNDRV_PCM_INFO_MMAP</constant> flag here. When the
hardware supports the interleaved or the non-interleaved
formats, <constant>SNDRV_PCM_INFO_INTERLEAVED</constant> or
@@ -2898,7 +2897,7 @@ struct _snd_pcm_runtime {
<para>
When the pcm supports the pause operation (given in the info
- field of the hardware table), the <constant>PAUSE_PUSE</constant>
+ field of the hardware table), the <constant>PAUSE_PUSH</constant>
and <constant>PAUSE_RELEASE</constant> commands must be
handled here, too. The former is the command to pause the pcm,
and the latter to restart the pcm again.
@@ -3085,7 +3084,7 @@ struct _snd_pcm_runtime {
<section id="pcm-interface-interrupt-handler-timer">
<title>High frequency timer interrupts</title>
<para>
- This happense when the hardware doesn't generate interrupts
+ This happens when the hardware doesn't generate interrupts
at the period boundary but issues timer interrupts at a fixed
timer rate (e.g. es1968 or ymfpci drivers).
In this case, you need to check the current hardware
@@ -3251,18 +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;
}
@@ -3278,35 +3278,35 @@ struct _snd_pcm_runtime {
<programlisting>
<![CDATA[
snd_pcm_hw_rule_add(substream->runtime, 0, SNDRV_PCM_HW_PARAM_CHANNELS,
- hw_rule_channels_by_format, 0, SNDRV_PCM_HW_PARAM_FORMAT,
- -1);
+ hw_rule_channels_by_format, NULL,
+ SNDRV_PCM_HW_PARAM_FORMAT, -1);
]]>
</programlisting>
</informalexample>
</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;
}
@@ -3321,8 +3321,8 @@ struct _snd_pcm_runtime {
<programlisting>
<![CDATA[
snd_pcm_hw_rule_add(substream->runtime, 0, SNDRV_PCM_HW_PARAM_FORMAT,
- hw_rule_format_by_channels, 0, SNDRV_PCM_HW_PARAM_CHANNELS,
- -1);
+ hw_rule_format_by_channels, NULL,
+ SNDRV_PCM_HW_PARAM_CHANNELS, -1);
]]>
</programlisting>
</informalexample>