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From: Takashi Sakamoto <o-takashi@sakamocchi.jp>
To: Oleksandr Andrushchenko <andr2000@gmail.com>,
	xen-devel@lists.xenproject.org, linux-kernel@vger.kernel.org,
	alsa-devel@alsa-project.org, jgross@suse.com,
	boris.ostrovsky@oracle.com, konrad.wilk@oracle.com,
	perex@perex.cz, tiwai@suse.com
Cc: Oleksandr Andrushchenko <oleksandr_andrushchenko@epam.com>
Subject: Re: [PATCH v3 5/6] ALSA: xen-front: Implement ALSA virtual sound driver
Date: Wed, 23 May 2018 13:00:45 +0900	[thread overview]
Message-ID: <510b107c-c136-7748-0cfa-9de849887c61@sakamocchi.jp> (raw)
In-Reply-To: <20180514062742.25879-6-andr2000@gmail.com>

Hi,

On May 14 2018 15:27, Oleksandr Andrushchenko wrote:
 > diff --git a/sound/xen/xen_snd_front_alsa.c 
b/sound/xen/xen_snd_front_alsa.c
 > new file mode 100644
 > index 000000000000..5041f83e98d2
 > --- /dev/null
 > +++ b/sound/xen/xen_snd_front_alsa.c
 > ...
 > +/*
 > + * FIXME: The mmaped data transfer is asynchronous and there is no
 > + * ack signal from user-space when it is done. This is the
 > + * reason it is not implemented in the PV driver as we do need
 > + * to know when the buffer can be transferred to the backend.
 > + */
 > ...

In ALSA PCM interface v2.0.14 or later, SNDRV_PCM_INFO_SYNC_APPLPTR is
available. This flag express that userspace applications are expected to
call ioctl(2) with 'SNDRV_PCM_IOCTL_SYNC_PTR' even if they oprate to
memory mapped page frames for PCM samples. For detail, please refer to a
commit 42f945970af9 ('ALSA: pcm: Add the explicit appl_ptr sync
support')[1].

As a supplement, please refer to below commits:
  * 4b671f577474 ('ALSA: pcm: Add an ioctl to specify the supported
    protocol version')[2]
  * b602aa8eb1a0 ('ALSA: pcm: Disable only control mmap for explicit
    appl_ptr sync')[3]

Alsa-lib v1.1.5 or later supports this flag and existent applications
can run transparently.

For developers, a tracepoint may be useful:
  * fccf53881e9b ('ALSA: pcm: add 'applptr' event of tracepoint')[4]

For your information.

[1] 
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=42f945970af9
[2] 
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=4b671f577474
[3] 
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=b602aa8eb1a0
[4] 
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=fccf53881e9b


Regards

Takashi Sakamoto

  parent reply	other threads:[~2018-05-23  4:00 UTC|newest]

Thread overview: 40+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-05-14  6:27 [PATCH v3 0/6] ALSA: xen-front: Add Xen para-virtualized frontend driver Oleksandr Andrushchenko
2018-05-14  6:27 ` [PATCH v3 1/6] ALSA: xen-front: Introduce Xen para-virtualized sound " Oleksandr Andrushchenko
2018-05-14  6:27 ` Oleksandr Andrushchenko
2018-05-14  6:27 ` [PATCH v3 2/6] ALSA: xen-front: Read sound driver configuration from Xen store Oleksandr Andrushchenko
2018-05-14  6:27 ` Oleksandr Andrushchenko
2018-05-14  6:27 ` [PATCH v3 3/6] ALSA: xen-front: Implement Xen event channel handling Oleksandr Andrushchenko
2018-05-14  6:27 ` Oleksandr Andrushchenko
2018-05-14  6:27 ` [PATCH v3 4/6] ALSA: xen-front: Implement handling of shared buffers Oleksandr Andrushchenko
2018-05-14 20:28   ` Takashi Iwai
2018-05-14 20:28   ` Takashi Iwai
2018-05-14 20:28     ` Takashi Iwai
2018-05-15  5:46     ` Oleksandr Andrushchenko
2018-05-15  6:01       ` Takashi Iwai
2018-05-15  6:02         ` Oleksandr Andrushchenko
2018-05-15  6:02         ` Oleksandr Andrushchenko
2018-05-17  6:26           ` Takashi Iwai
2018-05-17  6:33             ` Oleksandr Andrushchenko
2018-05-17  6:33             ` Oleksandr Andrushchenko
2018-05-17  6:33               ` Oleksandr Andrushchenko
2018-05-21 20:26             ` Takashi Iwai
2018-05-21 20:26             ` Takashi Iwai
2018-05-22  5:25               ` Oleksandr Andrushchenko
2018-05-22  5:25               ` Oleksandr Andrushchenko
2018-05-22  5:25                 ` Oleksandr Andrushchenko
2018-05-17  6:26           ` Takashi Iwai
2018-05-15  6:01       ` Takashi Iwai
2018-05-15  5:46     ` Oleksandr Andrushchenko
2018-05-14  6:27 ` Oleksandr Andrushchenko
2018-05-14  6:27 ` [PATCH v3 5/6] ALSA: xen-front: Implement ALSA virtual sound driver Oleksandr Andrushchenko
2018-05-23  4:00   ` Takashi Sakamoto
2018-05-23  4:00   ` Takashi Sakamoto [this message]
2018-05-23  6:14     ` Oleksandr Andrushchenko
2018-05-23  6:14     ` Oleksandr Andrushchenko
2018-05-14  6:27 ` Oleksandr Andrushchenko
2018-05-14  6:27 ` [PATCH v3 6/6] MAINTAINERS: Add ALSA: xen-front: maintainer entry Oleksandr Andrushchenko
2018-05-14  6:27 ` Oleksandr Andrushchenko
2018-05-14 15:52 ` [alsa-devel] [PATCH v3 0/6] ALSA: xen-front: Add Xen para-virtualized frontend driver Takashi Iwai
2018-05-14 15:52 ` Takashi Iwai
2018-05-14 16:08   ` Oleksandr Andrushchenko
2018-05-14 16:08   ` Oleksandr Andrushchenko

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