linux-kernel - Re: [PATCH 2/2] tpm: add driver for cr50 on SPI

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Date:	Thu, 21 Jul 2016 15:00:24 -0600
From:	Jason Gunthorpe <jgunthorpe@...idianresearch.com>
To:	Andrey Pronin <apronin@...omium.org>
Cc:	Jarkko Sakkinen <jarkko.sakkinen@...ux.intel.com>,
	Peter Huewe <peterhuewe@....de>,
	Marcel Selhorst <tpmdd@...horst.net>,
	tpmdd-devel@...ts.sourceforge.net, linux-kernel@...r.kernel.org,
	groeck@...omium.org, smbarber@...omium.org, dianders@...omium.org,
	Christophe Ricard <christophe.ricard@...il.com>
Subject: Re: [PATCH 2/2] tpm: add driver for cr50 on SPI

On Thu, Jul 21, 2016 at 11:10:47AM -0700, Andrey Pronin wrote:
> On Wed, Jul 20, 2016 at 11:03:36AM -0600, Jason Gunthorpe wrote:
> > On Tue, Jul 19, 2016 at 05:24:11PM -0700, Andrey Pronin wrote:
> > 
> > > The only two things that bother me with such approach are
> > > (1) whatever names I pick for the new set of functions, they
> > >     will be similar to and thus might be confused with the
> > >     original tpm_tis_read/writeXX;
> > 
> > tpm_tis_helper_read16 ?
> > 
> > > (2) these functions are phy-specific, so possibly it's better
> > >     to create tpm_tis_spi.h and put them there with proper
> > >     name prefixes. And then use in tpm_tis_spi and cr50_spi.
> > 
> > No, they are generic to any tis phy that implements read only through
> > read_bytes.
> > 
> > (Honestly, I'm not sure we made the best choice here having phy
> >  functions for all the versions, we are not that performance
> >  sensitive, just getting rid of everything but read_bytes from the
> >  phy_ops would probably also be a reasonable thing to do.)
> > 
> 
> One thing we can do is re-implement functions tpm_tis_read/writeXX
> to use phy-specific implementations of read16, read32, write32 if they
> are provided. But if those function pointers are left NULL in phy_ops,
> fallback to using read/write_bytes and byte-swapping.

I was thinking of just getting rid of phy_ops->read16 entirely and
only use read_bytes at the ops layer.

Jason