linux-kernel - Re: [RFC] ALSA: vsnd: Add Xen para-virtualized frontend driver

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Message-ID: <b229c2d1-7628-d6dd-73f1-94a4a4106f52@sakamocchi.jp>
Date:   Thu, 2 Nov 2017 18:44:05 +0900
From:   Takashi Sakamoto <o-takashi@...amocchi.jp>
To:     Oleksandr Andrushchenko <Oleksandr_Andrushchenko@...m.com>,
        tiwai@...e.com, alsa-devel@...a-project.org,
        linux-kernel@...r.kernel.org, xen-devel@...ts.xen.org,
        Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>
Cc:     Oleksandr Andrushchenko <andr2000@...il.com>,
        Oleksandr Grytsov <al1img@...il.com>,
        Clemens Ladisch <clemens@...isch.de>
Subject: Re: [RFC] ALSA: vsnd: Add Xen para-virtualized frontend driver

On Oct 30 2017 15:33, Oleksandr Andrushchenko wrote:
> This is an attempt to summarize previous discussions on Xen para-virtual
> sound driver.
> 
> A first attempt has been made to upstream the driver [1] which brought 
> number
> of fundamental questions, one of the biggest ones was that the frontend 
> driver
> has no means to synchronize its period elapsed event with the host driver,
> but uses software emulation on the guest side [2] with a timer.
> In order to address this a change to the existing Xen para-virtual sound
> protocol [3] was proposed to fill this gap [4] and remove emulation:
> 1. Introduced a new event channel from back to front
> 2. New event with number of bytes played/captured (XENSND_EVT_CUR_POS,
> to be used for sending snd_pcm_period_elapsed at frontend
> (in Linux implementation, sent in bytes, not frames to make the protocol
> generic and consistent)
> 3. New request for playback/capture control (XENSND_OP_TRIGGER) with
> start/pause/stop/resume sub-ops.
> 
> Along with these changes other comments on the driver were addressed,
> e.g. split into smaller chunks, moved the driver from misc to xen etc. [5].
> 
> Hope, this helps to get the full picture of what was discussed and makes it
> possible to move forward: if the approach seems ok, then I'll start
> upstreaming the changes to the sndif protocol and then will send the 
> updated
> version of the driver for the further review.

This message has below line in its header.

 > In-Reply-To: <e56a09e9-da66-b748-4e82-4b96a18cef32@...il.com>

This field is defined in RFC822[1], and recent mail clients use this 
header field to associate the message to a message which the field 
indicates. This results in a series of messages, so-called 'message 
thread'. Iwai-san would like you to start a new message thread for your 
topic. Would you please post this message again without the header field?

Generally, receiving no reactions means that readers/reviewers don't get 
enough information for your idea yet. (Of course, there's a probability 
that your work attracts no one...) In this case, submitting more 
resources is better, rather than requesting comments to them. For 
instance, you can point links to backend/frontend implementation as 
para-virtualization drivers which use the new feature of interface, if 
you did work for it. Indicating procedure to use a series of your work 
is better for test, if possible.

[1] https://www.ietf.org/rfc/rfc0822.txt

Regards

Takashi Sakamoto