linux-kernel - Re: [PATCH v4 2/6] tpm: tpm_tis_spi: Introduce a flow control callback

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Message-ID: <20190821181305.e6dgrez5n4ovtg5s@linux.intel.com>
Date:   Wed, 21 Aug 2019 21:13:05 +0300
From:   Jarkko Sakkinen <jarkko.sakkinen@...ux.intel.com>
To:     Stephen Boyd <swboyd@...omium.org>
Cc:     Peter Huewe <peterhuewe@....de>, linux-kernel@...r.kernel.org,
        linux-integrity@...r.kernel.org,
        Andrey Pronin <apronin@...omium.org>,
        Duncan Laurie <dlaurie@...omium.org>,
        Jason Gunthorpe <jgg@...pe.ca>, Arnd Bergmann <arnd@...db.de>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Guenter Roeck <groeck@...omium.org>,
        Alexander Steffen <Alexander.Steffen@...ineon.com>
Subject: Re: [PATCH v4 2/6] tpm: tpm_tis_spi: Introduce a flow control
 callback

On Mon, Aug 19, 2019 at 10:06:40AM -0700, Stephen Boyd wrote:
> > AFAIK the flow control is not part of the SPI standard itself but is
> > proprietary for each slave device. Thus, the flow control should be
> > documented to the source code. I do not want flow control mechanisms to
> > be multiplied before this is done.
> 
> Can you clarify this please? I don't understand what "the flow control
> should be documented to the source code" means.

Off the top of my head:

/* TCG SPI flow control is documented in the section 6.4 of [1]. However,
 * Google's CR50 chip has its own proprietary flow control. This struct
 * is used to bind the appropriate flow control mechanism.
 *
 * [1] https://trustedcomputinggroup.org/resource/pc-client-platform-tpm-profile-ptp-specification/
 */

> > 
> > The magic number 0x01 would be also good to get rid off.
> > 
> 
> Ok. What name should the #define be? I can make that another patch.

Do nothing. Not part of your patch set scope, was a stupid comment from
my side.

/Jarkko