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

[Oleksandr Andrushchenko <andr2000@gmail.com>]

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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