linux-kernel.vger.kernel.org archive mirror
 help / color / mirror / Atom feed
From: Clemens Ladisch <clemens@ladisch.de>
To: Oleksandr Andrushchenko <andr2000@gmail.com>
Cc: alsa-devel@alsa-project.org, xen-devel@lists.xen.org,
	linux-kernel@vger.kernel.org,
	Oleksandr Andrushchenko <oleksandr_andrushchenko@epam.com>,
	tiwai@suse.com
Subject: Re: [alsa-devel] [PATCH 08/11] ALSA: vsnd: Add timer for period interrupt emulation
Date: Mon, 7 Aug 2017 15:55:25 +0200	[thread overview]
Message-ID: <e857f6cf-0e82-aa2b-9291-6d0c40ac918a@ladisch.de> (raw)
In-Reply-To: <45738e58-7ed2-8315-8d9c-138c3d3a2ecc@gmail.com>

Oleksandr Andrushchenko wrote:
> On 08/07/2017 04:11 PM, Clemens Ladisch wrote:
>> How does that interface work?
>
> For the buffer received in .copy_user/.copy_kernel we send
> a request to the backend and get response back (async) when it has copied
> the bytes into HW/mixer/etc, so the buffer at frontend side can be reused.

So if the frontend sends too many (too large) requests, does the
backend wait until there is enough free space in the buffer before
it does the actual copying and then acks?

If yes, then these acks can be used as interrupts.  (You still
have to count frames, and call snd_pcm_period_elapsed() exactly
when a period boundary was reached or crossed.)

Splitting a large read/write into smaller requests to the backend
would improve the granularity of the known stream position.

The overall latency would be the sum of the sizes of the frontend
and backend buffers.


Why is the protocol designed this way?  Wasn't the goal to expose
some 'real' sound card?


Regards,
Clemens

  reply	other threads:[~2017-08-07 13:55 UTC|newest]

Thread overview: 21+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2017-08-07  7:43 [PATCH 00/11] ALSA: vsnd: Add Xen para-virtualized frontend driver Oleksandr Andrushchenko
2017-08-07  7:43 ` [PATCH 01/11] ALSA: vsnd: Implement driver's probe/remove Oleksandr Andrushchenko
2017-08-07  7:43 ` [PATCH 02/11] ALSA: vsnd: Implement Xen bus state handling Oleksandr Andrushchenko
2017-08-07  7:43 ` [PATCH 03/11] ALSA: vsnd: Read sound driver configuration from Xen store Oleksandr Andrushchenko
2017-08-07  7:43 ` [PATCH 04/11] ALSA: vsnd: Implement Xen event channel handling Oleksandr Andrushchenko
2017-08-07  7:43 ` [PATCH 05/11] ALSA: vsnd: Implement handling of shared buffers Oleksandr Andrushchenko
2017-08-07  7:43 ` [PATCH 06/11] ALSA: vsnd: Introduce ALSA virtual sound driver Oleksandr Andrushchenko
2017-08-07  7:43 ` [PATCH 07/11] ALSA: vsnd: Initialize virtul sound card Oleksandr Andrushchenko
2017-08-07  7:43 ` [PATCH 08/11] ALSA: vsnd: Add timer for period interrupt emulation Oleksandr Andrushchenko
2017-08-07 10:27   ` [alsa-devel] " Clemens Ladisch
2017-08-07 11:30     ` Oleksandr Andrushchenko
2017-08-07 13:11       ` Clemens Ladisch
2017-08-07 13:38         ` Oleksandr Andrushchenko
2017-08-07 13:55           ` Clemens Ladisch [this message]
2017-08-07 15:14             ` Oleksandr Andrushchenko
2017-08-08  6:09               ` Oleksandr Andrushchenko
2017-08-07  7:43 ` [PATCH 09/11] ALSA: vsnd: Implement ALSA PCM operations Oleksandr Andrushchenko
2017-08-07  7:43 ` [PATCH 10/11] ALSA: vsnd: Implement communication with backend Oleksandr Andrushchenko
2017-08-07  7:43 ` [PATCH 11/11] ALSA: vsnd: Introduce Kconfig option to enable Xen PV sound Oleksandr Andrushchenko
2017-08-07 11:28 ` [PATCH 00/11] ALSA: vsnd: Add Xen para-virtualized frontend driver Takashi Sakamoto
2017-08-07 11:33   ` Oleksandr Andrushchenko

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=e857f6cf-0e82-aa2b-9291-6d0c40ac918a@ladisch.de \
    --to=clemens@ladisch.de \
    --cc=alsa-devel@alsa-project.org \
    --cc=andr2000@gmail.com \
    --cc=linux-kernel@vger.kernel.org \
    --cc=oleksandr_andrushchenko@epam.com \
    --cc=tiwai@suse.com \
    --cc=xen-devel@lists.xen.org \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line before the message body. 
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).