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



On 03/20/2018 10:22 PM, Takashi Iwai wrote:
On Mon, 19 Mar 2018 08:22:19 +0100,
Oleksandr Andrushchenko wrote:
From: Oleksandr Andrushchenko <oleksandr_andrushchenko@xxxxxxxx>

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.
Thank you, I have tested the changes and need them to start upstreaming
the frontend driver used to test the protocol.
Do you mind if I put your Acked-by (or you prefer Reviewed-by?) tag to these patches:

[PATCH v3 4/5] sndif: Add explicit back and front synchronization
[PATCH v3 5/5] sndif: Add explicit back and front parameter negotiation

Please note, that the changes first to be merged into Xen and then I'll prepare
the same, but for the kernel

If other people have no concern, let's go ahead with FE/BE stuff.
Konrad, are you ok with the changes?

thanks,

Takashi
Thank you,
Oleksandr

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