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Re: [Xen-devel] [PATCH v15] This is the ABI for the two halves of a para-virtualized sound driver to communicate with each to other.



On 01/26/2017 01:54 PM, Dario Faggioli wrote:
On Thu, 2017-01-26 at 13:23 +0200, Oleksandr Andrushchenko wrote:
On 01/26/2017 01:09 PM, Dario Faggioli wrote:
On 01/24/2017 09:13 PM, Konrad Rzeszutek Wilk wrote:
On Mon, Dec 05, 2016 at 03:05:29PM +0200, Oleksandr
Andrushchenko wrote:
+ * Example for the frontend running in domain 5, instance of
the
driver
+ * in the front is 0 (single or first PV driver), device id
2,
+ * first stream (0):
+ * /local/domain/<frontend_id>/device/vsnd/<drv_idx>/
+ *         device/<dev_id>/stream/<stream_idx>/type = "p"
+ * /local/domain/5/device/vsnd/0/device/2/stream/0/type =
"p"
Why do you need 'device' ?
Could not this be:

/local/domain/5/device/vsnd/0/2/stream/0/type = "p" ?
then one has to know that "2" stands for device.
see above, I would keep "device" here
   /local/domain/5/device/vsnd/0/dev-2/stream-0/type = "p"

Or, with no '-':

   /local/domain/5/device/vsnd/0/dev2/stream0/type = "p"

Just my 2 cents...
1. Well, the only reason I have "device" here is for clarity
and consistency: sound card owns PCM devices, PCM device owns
streams
We could probably have "pcm-dev" instead of "device" here,
so we do not collide with xen device.

Sure. Or maybe even just 'pcm' (matter of taste, to large extent).
I would stick to "pcm-dev" then
2. "dev-%d" or "dev%d", "stream-%d" or "stream%d"
IMO, we already have indices employed in xenstore,
e.g. "domain/5", not "domain-5" or "domain5"
So, is the PCM device in question any different from domain
from this POV? To me - not, so this is why I use "device/%d"

True. Well, actually, have both. For instance, blkif, when multiqueue
is available are enabled, looks like this:

  /local/domain/1/device/vbd/0/multi-queue-num-queues = "2"
  /local/domain/1/device/vbd/0/queue-0 = ""
  /local/domain/1/device/vbd/0/queue-0/ring-ref = "<ring-ref#0>"
  /local/domain/1/device/vbd/0/queue-0/event-channel = "<evtchn#0>"
  /local/domain/1/device/vbd/0/queue-1 = ""
  /local/domain/1/device/vbd/0/queue-1/ring-ref = "<ring-ref#1>"
  /local/domain/1/device/vbd/0/queue-1/event-channel = "<evtchn#1>"
Yeap, I saw this and was in doubt
So, while I after all thing I agree with you on point 1) (i.e., on
having device, or pcm-dev, or pcm, the latter being my prefernce), I
think it would be ok to manage streams like blkif manages queues, and
hence using stream-0, stream-1, etc.
Ok, then we could have a formal rule for this: the last
enumeration should follow "XXX-%d" format, e.g. "queue-%d",
"stream-%d" etc. But entries, before this enum should follow
"YYY/%d" format.

Regards,
Dario


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