Re: [RFC PATCH v2 3/6] tpm: add send_recv() ops in tpm_class_ops

Jarkko Sakkinen
2025-03-07T16:32:13Z

On Fri, Mar 07, 2025 at 04:37:12PM +0100, Stefano Garzarella wrote:
> On Thu, Mar 06, 2025 at 11:52:46PM +0200, Jarkko Sakkinen wrote:
> > On Wed, Mar 05, 2025 at 03:02:29PM -0400, Jason Gunthorpe wrote:
> > > On Wed, Mar 05, 2025 at 10:04:25AM +0100, Stefano Garzarella wrote:
> > > > Jason suggested the send_recv() ops [2], which I liked, but if you prefer to
> > > > avoid that, I can restore what we did in v1 and replace the
> > > > TPM_CHIP_FLAG_IRQ hack with your point 2 (or use TPM_CHIP_FLAG_IRQ if you
> > > > think it is fine).
> > >
> > > I think it is a pretty notable simplification for the driver as it
> > > does not need to implement send, status, req_canceled and more ops.
> > >
> > > Given the small LOC on the core side I'd call that simplification a
> > > win..
> >
> > I'm sorry to disagree with you on this but adding a callback for
> > one leaf driver is not what I would call "a win" :-)
>
> IIUC in the ftpm driver (tpm_ftpm_tee.c) we could also use send_recv() and
> save a memcpy() to a temporally buffer (pvt_data->resp_buf) and also that 4k
> buffer allocated with the private data of the driver.
>
> BTW if you agree, for now I'll do something similar of what we do in the
> ftpm driver (which would be what Jarkko recommended - status() returns 0,
> .req_complete_mask = 0, .req_complete_val = 0) and we can discuss
> send_recv() in a new series where I can include changes for the ftpm driver
> too, to see whether it makes sense or not.
>
> WDYT?

Yeah, that would work. Althought not related to this callback interface
per se, also tpm-dev-common.c is one example (in a way).

>
> Thanks,
> Stefano

BR, Jarkko