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

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Message-ID: <7441b5ef-18d8-13aa-ef4d-40fe684c9218@intel.com>
Date:   Mon, 23 Jul 2018 14:38:08 -0700
From:   Tadeusz Struk <tadeusz.struk@...el.com>
To:     James Bottomley <James.Bottomley@...senPartnership.com>,
        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] tpm: add support for partial reads

On 07/23/2018 02:13 PM, James Bottomley wrote:
> The current patch does, you even provided a use case in your last email
>  (it's do command to get sizing followed by do command with correctly
> sized buffer). 

The example I provided was: #1 send a command, #2 read the response header
(10 bytes), get the actual response size from the header and then #3 read
the full response (response size - size of the header bytes).

> 
> However, if you tie it to O_NONBLOCK, it won't because no-one currently
> opens the TPM device non blocking so it's an ABI conformant
> discriminator of the uses.  Tying to O_NONBLOCK should be simple
> because it's in file->f_flags.

I think that it might be an option. Especially that I have this on top of
the async patch. Let's discuss this when Jarkko is back.

Thanks,
-- 
Tadeusz