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Subject: Re: [tpmdd-devel] [PATCH RFC v4 4/5] tpm: split out tpm-dev.c into
 tpm-dev.c and tpm-common-dev.c
From: James Bottomley <James.Bottomley@HansenPartnership.com>
To: Jason Gunthorpe <jgunthorpe@obsidianresearch.com>
Cc: linux-security-module@vger.kernel.org,
        tpmdd-devel@lists.sourceforge.net,
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Date: Mon, 23 Jan 2017 14:57:11 -0800
In-Reply-To: <20170123224952.GA21744@obsidianresearch.com>
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On Mon, 2017-01-23 at 15:49 -0700, Jason Gunthorpe wrote:
> On Mon, Jan 23, 2017 at 02:28:23PM -0800, James Bottomley wrote:
> > On Mon, 2017-01-23 at 09:47 -0700, Jason Gunthorpe wrote:
> > > On Mon, Jan 23, 2017 at 01:44:32AM +0200, Jarkko Sakkinen wrote:
> > > > From: James Bottomley <James.Bottomley@HansenPartnership.com>
> > > > 
> > > > Signed-off-by: James Bottomley
> > > > <James.Bottomley@HansenPartnership.com>
> > > 
> > > I really think we should not use the ugly read/write interface
> > > for 
> > > any new things.
> > 
> > The R/W interface is needed for backward compat,
> 
> With what? This is a new cdev with different semantics.

If you set TPM_DEVICE=/dev/tpms0 the old software just works.  If we
remove the R/W interface, nothing will work.  The point being the new
cdev has the same interface semantics, it just has different global
behavour.

James