Re: [RFC PATCH v2 1/9] crypto: qce: Add core driver implementation

[Stanimir Vabanov <svarbanov@mm-sol.com>]

Hi Herbert,

On 04/28/2014 11:59 AM, Herbert Xu wrote:
> On Mon, Apr 14, 2014 at 03:48:37PM +0300, Stanimir Varbanov wrote:
>>
>> +#define QCE_MAJOR_VERSION5	0x05
>> +#define QCE_QUEUE_LENGTH	50
> 
> What is the purpose of this software queue? Why can't you directly
> feed the requests to the hardware?
> 
> If the hardware can't handle more than 50 requests in-flight,
> then your software queue has failed to handle this since you're
> taking requests off the queue before you touch the hardware so
> you're not really limiting it to 50.  That is, for users that
> can wait you're potentially dropping their requests instead
> of letting them wait through the backlog mechanism.

My assumption was that crypto_ablkcipher_encrypt/decrypt couldn't sleep
and I should take the request almost immediately and return the
appropriate error value - EINPROGRESS if the hardware is idle and EBUSY
if the hardware working on some previous request. Thus if the returned
error is EBUSY and the request could be backlogged I should call
backlog->complete() when this request is taken actually for processing.

What I've done in practice is another story.

Is that assumption correct? If so, is crypto_enqueue|dequeue_request()
are the proper tools to implement this behaviour?

regards,
Stan