linux-kernel - Re: [PATCH v4 2/2] tpm: add support for partial reads

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Message-ID: <b0efbbf8-6242-a48d-d984-b49d5fb20bb8@intel.com>
Date:   Mon, 19 Nov 2018 08:44:49 -0800
From:   Tadeusz Struk <tadeusz.struk@...el.com>
To:     Jarkko Sakkinen <jarkko.sakkinen@...ux.intel.com>
Cc:     jgg@...pe.ca, linux-integrity@...r.kernel.org,
        linux-security-module@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v4 2/2] tpm: add support for partial reads

On 11/19/18 5:58 AM, Jarkko Sakkinen wrote:
> Please explain a scenario where "!ret_size" would no work given that
> both size and partial_data have always positive value?

Right, I only looked at the one line above before responding.
I'll change it to !ret_size

> 
> I don't understand. In order to maintain backwards compatibility you can
> send a new command at any time.

No, currently it is not possible to send a new command until the previous
response is consumed. -EBUSY is returned if one sends a new command before
reading the previous response (or at least part of it). See:
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/drivers/char/tpm/tpm-dev-common.c#n128

-- 
Tadeusz