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

[Jarkko Sakkinen]

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@xxxxxxxxxxxxxxxxxxxxx>
> > > 
> > > Signed-off-by: James Bottomley
> > > <James.Bottomley@xxxxxxxxxxxxxxxxxxxxx>
> > 
> > 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, so we don't really
> have a choice (well, it could go in for long term deprecation, but I
> found in SCSI that "long term" == "never").  I think no-one objects to
> the ioctl interface ... it's just no-one feels strongly enough to build
> and test it.  I'm sure if you send patches, Jarkko will include them.
> 
> James

I feel that it is incorrect to speak backwards compatibility because we
do no touch /dev/tpm0.

We can only speak about backwards compatibility only after the API for
tpms0 is in a kernel release. If someone uses that device, she must know
the constraints that it has.

/Jarkko