linux-kernel - Re: [RFC PATCH v2 3/6] tpm: add send_recv() ops in tpm_class

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Message-ID: <Z8oZLqn4p2-AWQbz@kernel.org>
Date: Thu, 6 Mar 2025 23:52:46 +0200
From: Jarkko Sakkinen <jarkko@...nel.org>
To: Jason Gunthorpe <jgg@...pe.ca>
Cc: Stefano Garzarella <sgarzare@...hat.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Claudio Carvalho <cclaudio@...ux.ibm.com>,
	Peter Huewe <peterhuewe@....de>, x86@...nel.org,
	Dov Murik <dovmurik@...ux.ibm.com>, linux-coco@...ts.linux.dev,
	Dionna Glaze <dionnaglaze@...gle.com>,
	James Bottomley <James.Bottomley@...senpartnership.com>,
	Ingo Molnar <mingo@...hat.com>, Joerg Roedel <jroedel@...e.de>,
	linux-integrity@...r.kernel.org, linux-kernel@...r.kernel.org,
	Dave Hansen <dave.hansen@...ux.intel.com>,
	Tom Lendacky <thomas.lendacky@....com>,
	Borislav Petkov <bp@...en8.de>, "H. Peter Anvin" <hpa@...or.com>
Subject: Re: [RFC PATCH v2 3/6] tpm: add send_recv() ops in tpm_class_ops

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" :-)

I mean, it's either a minor twist in

1. "the framework code" which affects in a way all other leaf drivers.
   At bare minimum it adds a tiny bit of complexity to the callback
   interface and a tiny bit of accumulated maintenance cost.
2. in the leaf driver

So I'd really would want to keep that tiny bit of extra complexity
localized.

> 
> Jason

BR, Jarkko