[alsa-devel] [RFC] ALSA: vsnd: Add Xen para-virtualized frontend driver

[Takashi Sakamoto]

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.

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 > In-Reply-To: <e56a09e9-da66-b748-4e82-4b96a18cef32 at gmail.com>

This field is defined in RFC822[1], and recent mail clients use this 
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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