linux-kernel - Re: [tpmdd-devel] [PATCH RFC 0/4] RFC: in-kernel resource manager

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Message-Id: <7a61bdf9-da82-c772-7e73-d4a4ffc25559@linux.vnet.ibm.com>
Date:   Wed, 11 Jan 2017 13:27:30 -0500
From:   Stefan Berger <stefanb@...ux.vnet.ibm.com>
To:     Jason Gunthorpe <jgunthorpe@...idianresearch.com>,
        Andreas Fuchs <andreas.fuchs@....fraunhofer.de>
Cc:     Ken Goldman <kgoldman@...ibm.com>, greg@...ellic.com,
        linux-kernel@...r.kernel.org,
        linux-security-module@...r.kernel.org,
        tpmdd-devel@...ts.sourceforge.net
Subject: Re: [tpmdd-devel] [PATCH RFC 0/4] RFC: in-kernel resource manager

On 01/11/2017 01:03 PM, Jason Gunthorpe wrote:
> On Wed, Jan 11, 2017 at 11:00:43AM +0100, Andreas Fuchs wrote:
>
>> could we please get an ioctl, that switches the "mode" of the fd entirely.
>> I'd like to see the write()/read() support still intact.
>> All my current code uses main-loop based poll on the fd and I don't want
>> to be force to start using threads...
> We currently do not support poll in the kernel for /dev/tpmX.
>
> ie we do not supply a poll method for 'struct file_operations'.
>
> Even worse, the current implementation blocks returning from write()
> until the TPM has completed its work, so it doesn't even make sense to
> combine it with poll.

Newer applications could issue an ioctl() after the open() to unblock 
the write().

     Stefan