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-rw-r--r--Documentation/sound/alsa/DocBook/writing-an-alsa-driver.tmpl184
1 files changed, 135 insertions, 49 deletions
diff --git a/Documentation/sound/alsa/DocBook/writing-an-alsa-driver.tmpl b/Documentation/sound/alsa/DocBook/writing-an-alsa-driver.tmpl
index 74d3a35b59bc..2c3fc3cb3b6b 100644
--- a/Documentation/sound/alsa/DocBook/writing-an-alsa-driver.tmpl
+++ b/Documentation/sound/alsa/DocBook/writing-an-alsa-driver.tmpl
@@ -18,8 +18,8 @@
</affiliation>
</author>
- <date>November 17, 2005</date>
- <edition>0.3.6</edition>
+ <date>September 10, 2007</date>
+ <edition>0.3.7</edition>
<abstract>
<para>
@@ -405,8 +405,9 @@
/* definition of the chip-specific record */
struct mychip {
struct snd_card *card;
- // rest of implementation will be in the section
- // "PCI Resource Managements"
+ /* rest of implementation will be in the section
+ * "PCI Resource Managements"
+ */
};
/* chip-specific destructor
@@ -414,7 +415,7 @@
*/
static int snd_mychip_free(struct mychip *chip)
{
- .... // will be implemented later...
+ .... /* will be implemented later... */
}
/* component-destructor
@@ -440,8 +441,9 @@
*rchip = NULL;
- // check PCI availability here
- // (see "PCI Resource Managements")
+ /* check PCI availability here
+ * (see "PCI Resource Managements")
+ */
....
/* allocate a chip-specific data with zero filled */
@@ -451,12 +453,13 @@
chip->card = card;
- // rest of initialization here; will be implemented
- // later, see "PCI Resource Managements"
+ /* rest of initialization here; will be implemented
+ * later, see "PCI Resource Managements"
+ */
....
- if ((err = snd_device_new(card, SNDRV_DEV_LOWLEVEL,
- chip, &ops)) < 0) {
+ err = snd_device_new(card, SNDRV_DEV_LOWLEVEL, chip, &ops);
+ if (err < 0) {
snd_mychip_free(chip);
return err;
}
@@ -490,7 +493,8 @@
return -ENOMEM;
/* (3) */
- if ((err = snd_mychip_create(card, pci, &chip)) < 0) {
+ err = snd_mychip_create(card, pci, &chip);
+ if (err < 0) {
snd_card_free(card);
return err;
}
@@ -502,10 +506,11 @@
card->shortname, chip->ioport, chip->irq);
/* (5) */
- .... // implemented later
+ .... /* implemented later */
/* (6) */
- if ((err = snd_card_register(card)) < 0) {
+ err = snd_card_register(card);
+ if (err < 0) {
snd_card_free(card);
return err;
}
@@ -605,7 +610,8 @@
<![CDATA[
struct mychip *chip;
....
- if ((err = snd_mychip_create(card, pci, &chip)) < 0) {
+ err = snd_mychip_create(card, pci, &chip);
+ if (err < 0) {
snd_card_free(card);
return err;
}
@@ -666,7 +672,8 @@
<informalexample>
<programlisting>
<![CDATA[
- if ((err = snd_card_register(card)) < 0) {
+ err = snd_card_register(card);
+ if (err < 0) {
snd_card_free(card);
return err;
}
@@ -1091,7 +1098,7 @@
static int snd_mychip_free(struct mychip *chip)
{
/* disable hardware here if any */
- .... // (not implemented in this document)
+ .... /* (not implemented in this document) */
/* release the irq */
if (chip->irq >= 0)
@@ -1119,7 +1126,8 @@
*rchip = NULL;
/* initialize the PCI entry */
- if ((err = pci_enable_device(pci)) < 0)
+ err = pci_enable_device(pci);
+ if (err < 0)
return err;
/* check PCI availability (28bit DMA) */
if (pci_set_dma_mask(pci, DMA_28BIT_MASK) < 0 ||
@@ -1141,7 +1149,8 @@
chip->irq = -1;
/* (1) PCI resource allocation */
- if ((err = pci_request_regions(pci, "My Chip")) < 0) {
+ err = pci_request_regions(pci, "My Chip");
+ if (err < 0) {
kfree(chip);
pci_disable_device(pci);
return err;
@@ -1156,10 +1165,10 @@
chip->irq = pci->irq;
/* (2) initialization of the chip hardware */
- .... // (not implemented in this document)
+ .... /* (not implemented in this document) */
- if ((err = snd_device_new(card, SNDRV_DEV_LOWLEVEL,
- chip, &ops)) < 0) {
+ err = snd_device_new(card, SNDRV_DEV_LOWLEVEL, chip, &ops);
+ if (err < 0) {
snd_mychip_free(chip);
return err;
}
@@ -1233,7 +1242,8 @@
<informalexample>
<programlisting>
<![CDATA[
- if ((err = pci_enable_device(pci)) < 0)
+ err = pci_enable_device(pci);
+ if (err < 0)
return err;
if (pci_set_dma_mask(pci, DMA_28BIT_MASK) < 0 ||
pci_set_consistent_dma_mask(pci, DMA_28BIT_MASK) < 0) {
@@ -1294,7 +1304,8 @@
<informalexample>
<programlisting>
<![CDATA[
- if ((err = pci_request_regions(pci, "My Chip")) < 0) {
+ err = pci_request_regions(pci, "My Chip");
+ if (err < 0) {
kfree(chip);
pci_disable_device(pci);
return err;
@@ -1322,7 +1333,7 @@
<programlisting>
<![CDATA[
if (request_irq(pci->irq, snd_mychip_interrupt,
- IRQF_DISABLED|IRQF_SHARED, "My Chip", chip)) {
+ IRQF_SHARED, "My Chip", chip)) {
printk(KERN_ERR "cannot grab irq %d\n", pci->irq);
snd_mychip_free(chip);
return -EBUSY;
@@ -1773,7 +1784,8 @@
struct snd_pcm_runtime *runtime = substream->runtime;
runtime->hw = snd_mychip_playback_hw;
- // more hardware-initialization will be done here
+ /* more hardware-initialization will be done here */
+ ....
return 0;
}
@@ -1781,7 +1793,8 @@
static int snd_mychip_playback_close(struct snd_pcm_substream *substream)
{
struct mychip *chip = snd_pcm_substream_chip(substream);
- // the hardware-specific codes will be here
+ /* the hardware-specific codes will be here */
+ ....
return 0;
}
@@ -1793,7 +1806,8 @@
struct snd_pcm_runtime *runtime = substream->runtime;
runtime->hw = snd_mychip_capture_hw;
- // more hardware-initialization will be done here
+ /* more hardware-initialization will be done here */
+ ....
return 0;
}
@@ -1801,7 +1815,8 @@
static int snd_mychip_capture_close(struct snd_pcm_substream *substream)
{
struct mychip *chip = snd_pcm_substream_chip(substream);
- // the hardware-specific codes will be here
+ /* the hardware-specific codes will be here */
+ ....
return 0;
}
@@ -1844,10 +1859,12 @@
{
switch (cmd) {
case SNDRV_PCM_TRIGGER_START:
- // do something to start the PCM engine
+ /* do something to start the PCM engine */
+ ....
break;
case SNDRV_PCM_TRIGGER_STOP:
- // do something to stop the PCM engine
+ /* do something to stop the PCM engine */
+ ....
break;
default:
return -EINVAL;
@@ -1900,8 +1917,8 @@
struct snd_pcm *pcm;
int err;
- if ((err = snd_pcm_new(chip->card, "My Chip", 0, 1, 1,
- &pcm)) < 0)
+ err = snd_pcm_new(chip->card, "My Chip", 0, 1, 1, &pcm);
+ if (err < 0)
return err;
pcm->private_data = chip;
strcpy(pcm->name, "My Chip");
@@ -1939,8 +1956,8 @@
struct snd_pcm *pcm;
int err;
- if ((err = snd_pcm_new(chip->card, "My Chip", 0, 1, 1,
- &pcm)) < 0)
+ err = snd_pcm_new(chip->card, "My Chip", 0, 1, 1, &pcm);
+ if (err < 0)
return err;
pcm->private_data = chip;
strcpy(pcm->name, "My Chip");
@@ -2097,7 +2114,7 @@
struct mychip *chip = snd_pcm_chip(pcm);
/* free your own data */
kfree(chip->my_private_pcm_data);
- // do what you like else
+ /* do what you like else */
....
}
@@ -2884,10 +2901,10 @@ struct _snd_pcm_runtime {
<![CDATA[
switch (cmd) {
case SNDRV_PCM_TRIGGER_START:
- // do something to start the PCM engine
+ /* do something to start the PCM engine */
break;
case SNDRV_PCM_TRIGGER_STOP:
- // do something to stop the PCM engine
+ /* do something to stop the PCM engine */
break;
default:
return -EINVAL;
@@ -3071,7 +3088,7 @@ struct _snd_pcm_runtime {
spin_unlock(&chip->lock);
snd_pcm_period_elapsed(chip->substream);
spin_lock(&chip->lock);
- // acknowledge the interrupt if necessary
+ /* acknowledge the interrupt if necessary */
}
....
spin_unlock(&chip->lock);
@@ -3134,7 +3151,7 @@ struct _snd_pcm_runtime {
snd_pcm_period_elapsed(substream);
spin_lock(&chip->lock);
}
- // acknowledge the interrupt if necessary
+ /* acknowledge the interrupt if necessary */
}
....
spin_unlock(&chip->lock);
@@ -3456,6 +3473,13 @@ struct _snd_pcm_runtime {
</para>
<para>
+ The <structfield>tlv</structfield> field can be used to provide
+ metadata about the control; see the
+ <link linkend="control-interface-tlv">
+ <citetitle>Metadata</citetitle></link> subsection.
+ </para>
+
+ <para>
The other three are
<link linkend="control-interface-callbacks"><citetitle>
callback functions</citetitle></link>.
@@ -3604,7 +3628,7 @@ struct _snd_pcm_runtime {
<title>Example of info callback</title>
<programlisting>
<![CDATA[
- static int snd_myctl_info(struct snd_kcontrol *kcontrol,
+ static int snd_myctl_mono_info(struct snd_kcontrol *kcontrol,
struct snd_ctl_elem_info *uinfo)
{
uinfo->type = SNDRV_CTL_ELEM_TYPE_BOOLEAN;
@@ -3639,7 +3663,7 @@ struct _snd_pcm_runtime {
<informalexample>
<programlisting>
<![CDATA[
- static int snd_myctl_info(struct snd_kcontrol *kcontrol,
+ static int snd_myctl_enum_info(struct snd_kcontrol *kcontrol,
struct snd_ctl_elem_info *uinfo)
{
static char *texts[4] = {
@@ -3658,6 +3682,16 @@ struct _snd_pcm_runtime {
</programlisting>
</informalexample>
</para>
+
+ <para>
+ Some common info callbacks are prepared for easy use:
+ <function>snd_ctl_boolean_mono_info()</function> and
+ <function>snd_ctl_boolean_stereo_info()</function>.
+ Obviously, the former is an info callback for a mono channel
+ boolean item, just like <function>snd_myctl_mono_info</function>
+ above, and the latter is for a stereo channel boolean item.
+ </para>
+
</section>
<section id="control-interface-callbacks-get">
@@ -3794,7 +3828,8 @@ struct _snd_pcm_runtime {
<informalexample>
<programlisting>
<![CDATA[
- if ((err = snd_ctl_add(card, snd_ctl_new1(&my_control, chip))) < 0)
+ err = snd_ctl_add(card, snd_ctl_new1(&my_control, chip));
+ if (err < 0)
return err;
]]>
</programlisting>
@@ -3843,6 +3878,56 @@ struct _snd_pcm_runtime {
</para>
</section>
+ <section id="control-interface-tlv">
+ <title>Metadata</title>
+ <para>
+ To provide information about the dB values of a mixer control, use
+ on of the <constant>DECLARE_TLV_xxx</constant> macros from
+ <filename>&lt;sound/tlv.h&gt;</filename> to define a variable
+ containing this information, set the<structfield>tlv.p
+ </structfield> field to point to this variable, and include the
+ <constant>SNDRV_CTL_ELEM_ACCESS_TLV_READ</constant> flag in the
+ <structfield>access</structfield> field; like this:
+ <informalexample>
+ <programlisting>
+<![CDATA[
+ static DECLARE_TLV_DB_SCALE(db_scale_my_control, -4050, 150, 0);
+
+ static struct snd_kcontrol_new my_control __devinitdata = {
+ ...
+ .access = SNDRV_CTL_ELEM_ACCESS_READWRITE |
+ SNDRV_CTL_ELEM_ACCESS_TLV_READ,
+ ...
+ .tlv.p = db_scale_my_control,
+ };
+]]>
+ </programlisting>
+ </informalexample>
+ </para>
+
+ <para>
+ The <function>DECLARE_TLV_DB_SCALE</function> macro defines
+ information about a mixer control where each step in the control's
+ value changes the dB value by a constant dB amount.
+ The first parameter is the name of the variable to be defined.
+ The second parameter is the minimum value, in units of 0.01 dB.
+ The third parameter is the step size, in units of 0.01 dB.
+ Set the fourth parameter to 1 if the minimum value actually mutes
+ the control.
+ </para>
+
+ <para>
+ The <function>DECLARE_TLV_DB_LINEAR</function> macro defines
+ information about a mixer control where the control's value affects
+ the output linearly.
+ The first parameter is the name of the variable to be defined.
+ The second parameter is the minimum value, in units of 0.01 dB.
+ The third parameter is the maximum value, in units of 0.01 dB.
+ If the minimum value mutes the control, set the second parameter to
+ <constant>TLV_DB_GAIN_MUTE</constant>.
+ </para>
+ </section>
+
</chapter>
@@ -3880,7 +3965,7 @@ struct _snd_pcm_runtime {
{
struct mychip *chip = ac97->private_data;
....
- // read a register value here from the codec
+ /* read a register value here from the codec */
return the_register_value;
}
@@ -3889,7 +3974,7 @@ struct _snd_pcm_runtime {
{
struct mychip *chip = ac97->private_data;
....
- // write the given register value to the codec
+ /* write the given register value to the codec */
}
static int snd_mychip_ac97(struct mychip *chip)
@@ -3902,7 +3987,8 @@ struct _snd_pcm_runtime {
.read = snd_mychip_ac97_read,
};
- if ((err = snd_ac97_bus(chip->card, 0, &ops, NULL, &bus)) < 0)
+ err = snd_ac97_bus(chip->card, 0, &ops, NULL, &bus);
+ if (err < 0)
return err;
memset(&ac97, 0, sizeof(ac97));
ac97.private_data = chip;
@@ -4447,10 +4533,10 @@ struct _snd_pcm_runtime {
<informalexample>
<programlisting>
<![CDATA[
- struct list_head *list;
struct snd_rawmidi_substream *substream;
- list_for_each(list, &rmidi->streams[SNDRV_RAWMIDI_STREAM_OUTPUT].substreams) {
- substream = list_entry(list, struct snd_rawmidi_substream, list);
+ list_for_each_entry(substream,
+ &rmidi->streams[SNDRV_RAWMIDI_STREAM_OUTPUT].substreams,
+ list {
sprintf(substream->name, "My MIDI Port %d", substream->number + 1);
}
/* same for SNDRV_RAWMIDI_STREAM_INPUT */