[PATCH] Allow ioplugins to override snd_pcm_delay()

[PATCH] Allow ioplugins to override snd_pcm_delay()

[Pierre Ossman]

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Some io plug-ins might want to adjust the reported delay value and not
strictly follow the current buffer usage (that's why we have two calls
after all).

Allow them to specify a delay() callback and use the previous behaviour
if they don't.

Signed-off-by: Pierre Ossman <ossman@cendio.se>


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? ioplug-delay.patch
Index: include/pcm_ioplug.h
===================================================================
RCS file: /cvsroot/alsa/alsa-lib/include/pcm_ioplug.h,v
retrieving revision 1.5
diff -u -r1.5 pcm_ioplug.h
--- include/pcm_ioplug.h	24 May 2005 09:42:01 -0000	1.5
+++ include/pcm_ioplug.h	25 May 2006 19:05:23 -0000
@@ -130,6 +130,10 @@
 	 */
 	snd_pcm_sframes_t (*pointer)(snd_pcm_ioplug_t *io);
 	/**
+	 * get the delay for the running PCM; optional
+	 */
+	int (*delay)(snd_pcm_ioplug_t *io, snd_pcm_sframes_t *delayp);
+	/**
 	 * transfer the data; optional
 	 */
 	snd_pcm_sframes_t (*transfer)(snd_pcm_ioplug_t *io,
Index: src/pcm/pcm_ioplug.c
===================================================================
RCS file: /cvsroot/alsa/alsa-lib/src/pcm/pcm_ioplug.c,v
retrieving revision 1.10
diff -u -r1.10 pcm_ioplug.c
--- src/pcm/pcm_ioplug.c	28 Jun 2005 10:24:45 -0000	1.10
+++ src/pcm/pcm_ioplug.c	25 May 2006 19:05:24 -0000
@@ -106,8 +106,14 @@
 
 static int snd_pcm_ioplug_delay(snd_pcm_t *pcm, snd_pcm_sframes_t *delayp)
 {
-	snd_pcm_ioplug_hw_ptr_update(pcm);
-	*delayp = snd_pcm_mmap_hw_avail(pcm); 
+	ioplug_priv_t *io = pcm->private_data;
+
+	if (io->data->callback->delay)
+		return io->data->callback->delay(io->data, delayp);
+	else {
+		snd_pcm_ioplug_hw_ptr_update(pcm);
+		*delayp = snd_pcm_mmap_hw_avail(pcm);
+	}
 	return 0;
 }
 

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Re: [PATCH] Allow ioplugins to override snd_pcm_delay()

[Takashi Iwai]

At Fri, 26 May 2006 11:38:11 +0200,
Pierre Ossman wrote:
> 
> Some io plug-ins might want to adjust the reported delay value and not
> strictly follow the current buffer usage (that's why we have two calls
> after all).
> 
> Allow them to specify a delay() callback and use the previous behaviour
> if they don't.
> 
> Signed-off-by: Pierre Ossman <ossman@cendio.se>
> 
> ? ioplug-delay.patch
> Index: include/pcm_ioplug.h
> ===================================================================
> RCS file: /cvsroot/alsa/alsa-lib/include/pcm_ioplug.h,v
> retrieving revision 1.5
> diff -u -r1.5 pcm_ioplug.h
> --- include/pcm_ioplug.h	24 May 2005 09:42:01 -0000	1.5
> +++ include/pcm_ioplug.h	25 May 2006 19:05:23 -0000
> @@ -130,6 +130,10 @@
>  	 */
>  	snd_pcm_sframes_t (*pointer)(snd_pcm_ioplug_t *io);
>  	/**
> +	 * get the delay for the running PCM; optional
> +	 */
> +	int (*delay)(snd_pcm_ioplug_t *io, snd_pcm_sframes_t *delayp);
> +	/**
>  	 * transfer the data; optional
>  	 */
>  	snd_pcm_sframes_t (*transfer)(snd_pcm_ioplug_t *io,

The change is OK, but please remind that the API has been already
public, so we need to keep the compatibility as much as possible.
This addition will break the binary compatibility.

First, we need the increase of version number
(SND_PCM_IOPLUG_VERSION) if we modify API.  If the version of the
object is older, either reject or allow it as compatible.

One way to keep it binary-compatible is to append the new method to
the end of the callback table, and check the version before accessing
the new method (and handle as NULL for older version).

Could you rewrite the patch in that manner?


Thanks,

Takashi

Re: [PATCH] Allow ioplugins to override snd_pcm_delay()

[Pierre Ossman]

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Takashi Iwai wrote:
> 
> The change is OK, but please remind that the API has been already
> public, so we need to keep the compatibility as much as possible.
> This addition will break the binary compatibility.
> 
> First, we need the increase of version number
> (SND_PCM_IOPLUG_VERSION) if we modify API.  If the version of the
> object is older, either reject or allow it as compatible.
> 
> One way to keep it binary-compatible is to append the new method to
> the end of the callback table, and check the version before accessing
> the new method (and handle as NULL for older version).
> 
> Could you rewrite the patch in that manner?
> 

No problem. I'll have it fixed later this afternoon.

-- 
Rgds
Pierre Ossman                Telephone: +46-13-21 46 00
Cendio AB                    Web: http://www.cendio.com


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Re: [PATCH] Allow ioplugins to override snd_pcm_delay()

[Pierre Ossman]

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Takashi Iwai wrote:
> 
> First, we need the increase of version number
> (SND_PCM_IOPLUG_VERSION) if we modify API.  If the version of the
> object is older, either reject or allow it as compatible.
> 

The headers do not detail how versions are managed here. Which component
of the version number should I increase?

-- 
Rgds
Pierre Ossman                Telephone: +46-13-21 46 00
Cendio AB                    Web: http://www.cendio.com


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Re: [PATCH] Allow ioplugins to override snd_pcm_delay()

[Takashi Iwai]

At Fri, 26 May 2006 14:35:20 +0200,
Pierre Ossman wrote:
> 
> Takashi Iwai wrote:
> > 
> > First, we need the increase of version number
> > (SND_PCM_IOPLUG_VERSION) if we modify API.  If the version of the
> > object is older, either reject or allow it as compatible.
> > 
> 
> The headers do not detail how versions are managed here. Which component
> of the version number should I increase?

I think TINY should suffice in this case.
It's just a minor addition.


Takashi

Re: [PATCH] Allow ioplugins to override snd_pcm_delay()

[James Courtier-Dutton]

Pierre Ossman wrote:
> Some io plug-ins might want to adjust the reported delay value and not
> strictly follow the current buffer usage (that's why we have two calls
> after all).
>
> Allow them to specify a delay() callback and use the previous behaviour
> if they don't.
>
> Signed-off-by: Pierre Ossman <ossman@cendio.se>
>   
Can you give an example of a plugin that would want to adjust the delay 
value?

James

Re: [PATCH] Allow ioplugins to override snd_pcm_delay()

[Pierre Ossman]

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James Courtier-Dutton wrote:
> Pierre Ossman wrote:
>> Some io plug-ins might want to adjust the reported delay value and not
>> strictly follow the current buffer usage (that's why we have two calls
>> after all).
>>
>> Allow them to specify a delay() callback and use the previous behaviour
>> if they don't.
>>
>> Signed-off-by: Pierre Ossman <ossman@cendio.se>
>>   
> Can you give an example of a plugin that would want to adjust the delay
> value?
> 

The polypaudio backend, which is why I submitted this patch.

The recently released padsp (esddsp-equivalent) has much better latency
reporting than the ALSA to polypaudio plug-in. And we just can't have
OSS applications outperforming ALSA ones. ;)

-- 
Pierre Ossman                Telephone: +46-13-21 46 00
Cendio AB                    Web: http://www.cendio.com


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[PATCH] Allow ioplugins to override snd_pcm_delay()

[Pierre Ossman]

[-- Attachment #1.1.1: Type: text/plain, Size: 299 bytes --]

Some io plug-ins might want to adjust the reported delay value and not
strictly follow the current buffer usage (that's why we have two calls
after all).

Allow them to specify a delay() callback and use the previous behaviour
if they don't.

Signed-off-by: Pierre Ossman <ossman@cendio.se>

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Index: src/pcm/pcm_ioplug.c
===================================================================
RCS file: /cvsroot/alsa/alsa-lib/src/pcm/pcm_ioplug.c,v
retrieving revision 1.10
diff -u -r1.10 pcm_ioplug.c
--- src/pcm/pcm_ioplug.c	28 Jun 2005 10:24:45 -0000	1.10
+++ src/pcm/pcm_ioplug.c	26 May 2006 13:59:14 -0000
@@ -106,8 +106,15 @@
 
 static int snd_pcm_ioplug_delay(snd_pcm_t *pcm, snd_pcm_sframes_t *delayp)
 {
-	snd_pcm_ioplug_hw_ptr_update(pcm);
-	*delayp = snd_pcm_mmap_hw_avail(pcm); 
+	ioplug_priv_t *io = pcm->private_data;
+
+	if ((io->data->version >= 0x010001) &&
+		(io->data->callback->delay))
+		return io->data->callback->delay(io->data, delayp);
+	else {
+		snd_pcm_ioplug_hw_ptr_update(pcm);
+		*delayp = snd_pcm_mmap_hw_avail(pcm);
+	}
 	return 0;
 }
 
@@ -872,7 +879,9 @@
 	       ioplug->callback->stop &&
 	       ioplug->callback->pointer);
 
-	if (ioplug->version != SND_PCM_IOPLUG_VERSION) {
+	/* We support 1.0.0 to current */
+	if ((ioplug->version < 0x010000) ||
+		(ioplug->version > SND_PCM_IOPLUG_VERSION)) {
 		SNDERR("ioplug: Plugin version mismatch\n");
 		return -ENXIO;
 	}
Index: include/pcm_ioplug.h
===================================================================
RCS file: /cvsroot/alsa/alsa-lib/include/pcm_ioplug.h,v
retrieving revision 1.5
diff -u -r1.5 pcm_ioplug.h
--- include/pcm_ioplug.h	24 May 2005 09:42:01 -0000	1.5
+++ include/pcm_ioplug.h	26 May 2006 13:59:14 -0000
@@ -65,7 +65,7 @@
  */
 #define SND_PCM_IOPLUG_VERSION_MAJOR	1	/**< Protocol major version */
 #define SND_PCM_IOPLUG_VERSION_MINOR	0	/**< Protocol minor version */
-#define SND_PCM_IOPLUG_VERSION_TINY	0	/**< Protocol tiny version */
+#define SND_PCM_IOPLUG_VERSION_TINY	1	/**< Protocol tiny version */
 /**
  * IO-plugin protocol version
  */
@@ -184,6 +184,10 @@
 	 * dump; optional
 	 */
 	void (*dump)(snd_pcm_ioplug_t *io, snd_output_t *out);
+	/**
+	 * get the delay for the running PCM; optional
+	 */
+	int (*delay)(snd_pcm_ioplug_t *io, snd_pcm_sframes_t *delayp);
 };
 
 

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Re: [PATCH] Allow ioplugins to override snd_pcm_delay()

[Takashi Iwai]

At Fri, 26 May 2006 16:01:16 +0200,
Pierre Ossman wrote:
> 
> Some io plug-ins might want to adjust the reported delay value and not
> strictly follow the current buffer usage (that's why we have two calls
> after all).
> 
> Allow them to specify a delay() callback and use the previous behaviour
> if they don't.
> 
> Signed-off-by: Pierre Ossman <ossman@cendio.se>


Thanks, applied to HG repo with minor space fixes.


Takashi