Re: [PATCH 2/3] xen/kbdif: Add unique input device identifier

From: Oleksandr Andrushchenko <andr2000@gmail.com>
To: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Cc: xen-devel@lists.xenproject.org,
	Oleksandr Andrushchenko <oleksandr_andrushchenko@epam.com>
Subject: Re: [PATCH 2/3] xen/kbdif: Add unique input device identifier
Date: Thu, 7 Jun 2018 16:40:48 +0300	[thread overview]
Message-ID: <4b08084c-8719-47c2-cf64-cced0f0005a3@gmail.com> (raw)
In-Reply-To: <20180607132845.GA24186@char.us.oracle.com>

On 06/07/2018 04:28 PM, Konrad Rzeszutek Wilk wrote:
> On Wed, May 23, 2018 at 09:19:22AM +0300, Oleksandr Andrushchenko wrote:
>> From: Oleksandr Andrushchenko <oleksandr_andrushchenko@epam.com>
>>
>> If frontend is configured to expose multiple input device instances
>> then backend may require a way to uniquely identify concrete input
>> device within the frontend. This is useful for use-cases where
>> virtual input device needs to be matched to physical input device.
>> Add XenBus "unique-id" node parameter, so this sort of use-cases can
>> be implemented.
>>
>> Signed-off-by: Oleksandr Andrushchenko <oleksandr_andrushchenko@epam.com>
>> ---
>>   xen/include/public/io/kbdif.h | 10 ++++++++++
>>   1 file changed, 10 insertions(+)
>>
>> diff --git a/xen/include/public/io/kbdif.h b/xen/include/public/io/kbdif.h
>> index a68da0f1a37f..45e4ff5b0a05 100644
>> --- a/xen/include/public/io/kbdif.h
>> +++ b/xen/include/public/io/kbdif.h
>> @@ -82,6 +82,15 @@
>>    *      for pointer devices should set this to 1. Raw (unscaled) values have
>>    *      a range of [0, 0x7fff].
>>    *
>> + *-----------------------  Device Instance Parameters ------------------------
>> + *
>> + * unique-id
>> + *      Values:         <uint32_t>
> Wouldn't a string be easier? That way you can extend this in the future
> to also have an UUID or so?
Much easier. We were thinking about that as well, but sndif already has it
as uint32_t. If you are ok to change uniquie-id for sndif to string then 
that
would be much better: UUID as you mention + all protocols have unique-id
consistently defined as string.
sndif's unique-id is not used by the frontend driver and we are about
to start libx/xl support for sound, so I think this is the right time for
such a change.
If you are fine with that then I'll send yet another patch for sndif.
>> + *
>> + *      After device instance initialization it is assigned a unique ID
>> + *      (within the front driver), so every instance of the frontend can be
>> + *      identified by the backend by this ID.
>> + *
>>    *------------------------- Pointer Device Parameters ------------------------
>>    *
>>    * width
>> @@ -204,6 +213,7 @@
>>   #define XENKBD_FIELD_MT_WIDTH          "multi-touch-width"
>>   #define XENKBD_FIELD_MT_HEIGHT         "multi-touch-height"
>>   #define XENKBD_FIELD_MT_NUM_CONTACTS   "multi-touch-num-contacts"
>> +#define XENKBD_FIELD_UNIQUE_ID         "unique-id"
>>   
>>   /* OBSOLETE, not recommended for use */
>>   #define XENKBD_FIELD_RING_REF          "page-ref"
>> -- 
>> 2.17.0
>>


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