linux-kernel - Re: [PATCH 2/2] tpm/tpm_ftpm_tee: use send

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Message-ID: <Z-QkGUenPAMid63l@kernel.org>
Date: Wed, 26 Mar 2025 17:58:28 +0200
From: Jarkko Sakkinen <jarkko@...nel.org>
To: Jason Gunthorpe <jgg@...pe.ca>
Cc: Sumit Garg <sumit.garg@...nel.org>,
	Stefano Garzarella <sgarzare@...hat.com>,
	linux-kernel@...r.kernel.org, Peter Huewe <peterhuewe@....de>,
	linux-integrity@...r.kernel.org,
	James Bottomley <James.Bottomley@...senpartnership.com>,
	Jens Wiklander <jens.wiklander@...aro.org>
Subject: Re: [PATCH 2/2] tpm/tpm_ftpm_tee: use send_recv() op

On Wed, Mar 26, 2025 at 04:57:47PM +0200, Jarkko Sakkinen wrote:
> On Wed, Mar 26, 2025 at 11:34:01AM -0300, Jason Gunthorpe wrote:
> > On Wed, Mar 26, 2025 at 02:11:12PM +0200, Jarkko Sakkinen wrote:
> > 
> > > Generally speaking I don't see enough value in complicating
> > > callback interface. It's better to handle complications in
> > > the leaves (i.e. dictatorship of majority ;-) ).
> > 
> > That is very much not the way most driver subsystems view the
> > world. We want to pull logical things into the core code and remove
> > them from drivers to make the drivers simpler and more robust.
> > 
> > The amount of really dumb driver boiler plate that this series
> > obviously removes is exactly the sort of stuff we should be fixing by
> > improving the core code.
> > 
> > The callback interface was never really sanely designed, it was just
> > built around the idea of pulling the timout processing into the core
> > code for TIS hardware. It should be revised to properly match these
> > new HW types that don't have this kind of timeout mechanism.
> 
> Both TIS and CRB, which are TCG standards and they span to many
> different types of drivers and busses. I don't have the figures but
> probably they cover vast majority of the hardware.
> 
> We are talking about 39 lines of reduced complexity at the cost
> of complicating branching at the top level. I doubt that there
> is either any throughput or latency issues.
> 
> What is measurable benefit? The rationale is way way too abstract
> for me to cope, sorry.

E.g., here's how you can get rid of extra cruft in tpm_ftpm_tee w/o
any new callbacks.

BR, Jarkko

View attachment "0001-tpm-Make-chip-status-cancel-req_canceled-opt.patch" of type "text/x-diff" (3402 bytes)