Re: [PATCHv9 2/4] mailbox: Introduce framework for mailbox

[Sudeep Holla <sudeep.holla@arm.com>]

On 01/08/14 13:28, Jassi Brar wrote:
> On 1 August 2014 15:09, Sudeep Holla <sudeep.holla@arm.com> wrote:
>> On 31/07/14 18:58, Jassi Brar wrote:
>
>>>>
>>>> Probably this is discussed already, but again I missed to find it
>>>> in archives, so asking here. If the protocol has some payload associated
>>>> with the message and controller expects it to be in place before calling
>>>> send_data, we essentially end up not using this queue at all by waiting
>>>> in the protocol layer(may be in it's own queue)
>>>>
>>> Why essentially?
>>>     The 'data' is a void *  i.o.w the packet format is a completely
>>> internal understanding between a controller and a client. The 'data'
>>> can point to a copy of payload that the controller driver sets up in
>>> the shared payload region as the first thing in send_data() callback.
>>> OR, like my 'server' type platform, where the access is serialized to
>>> the shared payload region.
>>>
>>
>> Yes that's exactly what I have now. But based on your driver I thought
>> that the shared memory should not be associated with the mailbox controller
>> and should be completely handled in the protocol/client.
>>
>> Also to handle async packet from remote, controller has to pass shared
>> memory pointer always to the client to read the data as the buffer won't
>> to ready in such case. So I thought it's good idea to handle shared memory
>> completely in client/protocol.
>>
> Again ur platform has the freedom. The async client should have a free
> packet to copy the data as soon as it arrives.
> My platform divides the SHM into two parts - one for each direction.
>

I understand that, but I wanted to know what's the general
recommendation for mailbox controller drivers. Do they need to be
associated with the shared memory or is it left the protocol ?

The main reason I am asking is that the MHU driver you had didn't
deal with any shared memory. That's fine and if we want to make that
common/generic we need to know if we are going to handle shared
memory in there or leave it to client/protocol implementations.

Regards.
Sudeep