[alsa-devel] [Xen-devel][PATCH v3 0/5] sndif: add explicit back and front synchronization

[Takashi Iwai]

On Mon, 19 Mar 2018 08:22:19 +0100,
Oleksandr Andrushchenko wrote:
> 
> From: Oleksandr Andrushchenko <oleksandr_andrushchenko at epam.com>
> 
> Hello, all!
> 
> In order to provide explicit synchronization between backend and
> frontend the following changes are introduced in the protocol:
>  - bump protocol version to 2
>  - add new ring buffer for sending asynchronous events from
>    backend to frontend to report number of bytes played by the
>    frontend (XENSND_EVT_CUR_POS)
>  - introduce trigger events for playback control: start/stop/pause/resume
>  - add "req-" prefix to event-channel and ring-ref to unify naming
>    of the Xen event channels for requests and events
>  - add XENSND_OP_HW_PARAM_QUERY request to read/update
>    stream configuration space: request passes desired intervals/formats for
>    the stream parameters and the response returns allowed intervals and
>    formats mask that can be used.
> 
> Changes since v2:
> 1. Konrad's r-b tag for version patch
> 2. MAJOR: changed req/resp/evt packet sizes from 32 to 64 octets
> 3. Reworked XENSND_OP_HW_PARAM_QUERY so it now sends all 
>    parameters at once, allowing to check all the configuration
>    space.
> 4. Minor documentation cleanup (added missed "reserved" fields)
> 
> Changes since v1:
> 
> 1. Changed protocol version definition from string to integer,
> so it can easily be used in comparisons.
> Konrad, I have removed your r-b tag for the reason of this change.
> 
> 2. In order to provide explicit stream parameter negotiation between
> backend and frontend the following changes are introduced in the protocol:
> add XENSND_OP_HW_PARAM_QUERY request to read/update
> configuration space for the parameter given: request passes
> desired parameter interval (mask) and the response to this request
> returns min/max interval (mask) for the parameter to be used.
> 
> Parameters supported by this request/response:
>  - format mask
>  - sample rate interval
>  - number of channels interval
>  - buffer size, interval, frames
>  - period size, interval, frames

I can't judge exactly about the protocol without the actual FE/BE
implementations, but the change looks good to me, especially if you've
already tested something.

If other people have no concern, let's go ahead with FE/BE stuff.


thanks,

Takashi