Users of SBE FIFO kernel driver

[Joel Stanley]

On Thu, Feb 2, 2017 at 3:18 PM, Alistair Popple <alistair at popple.id.au> wrote:
> On Thu, 2 Feb 2017 01:59:08 PM Joel Stanley wrote:
>> Hi Chris,
>>
>> On Thu, Feb 2, 2017 at 5:58 AM, Christopher Bostic
>> <cbostic at linux.vnet.ibm.com> wrote:
>> > I've not seen this discussed in the group but if this has already been
>> > determined than any pointers to the latest documentation would be
>> > appreciated.
>> >
>> > Who are all the potential users of the OpenBMC SBE FIFO device driver?   I
>> > understand it will need to export its general submit interface to other
>> > kernel drivers.  Only one I know of for sure would be the OCC driver Eddie
>> > James is working on.
>>
>> In addition to Eddie's driver, in userspace we will have the code that
>> performs the power on sequence.
>>
>> > Any others?
>> > What about user space access of the SBE FIFO engine?  What apps would
>> > require it?  Cronus I assume will need some means to directly access it.
>>
>> We want userspace API and an in-kernel API.
>
> Yep. For example as Ben mentioned the chip-ops also use the SBE FIFO. However
> we certainly don't want to put chip-ops directly in the kernel. It makes more
> sense to use a userspace SBE FIFO API to do the chips-ops, power on sequence
> etc. from userspace.
>
>> The driver you design will need to take into account that there will
>> be multiple users from each of these APIs. For instance, there will be
>> Eddie's OCC hwmon driver and the userspace code that kicks off the
>> boot sequence.

Agreed. This driver is to control access to the FIFO. We don't want to
have to modify the kernel every time a new operation is required.

The programs sending the messages will know how to encode their own
operations, such as pdbg, the occ hwmon driver, etc.

Cheers,

Joel