Re: [tpmdd-devel] [PATCH RFC v4 4/5] tpm: split out tpm-dev.c into tpm-dev.c and tpm-common-dev.c

Jason Gunthorpe
2017-01-23T23:04:53Z

On Mon, Jan 23, 2017 at 02:57:11PM -0800, James Bottomley wrote:
> 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.

So you are saying there is so much already deployed TPM2 software that
has this TPM_DEVICE env var convention that we need to support it with
compat?

I'm really surprised by that.. But OK.

Can you at least remove the 'user_read_timer' junk from the new cdev?

Jason