Re: [tpmdd-devel] [PATCH] tpm: remove chip_num parameter from in-kernel API

On Tue, Oct 24, 2017 at 10:02:00AM -0700, Dmitry Torokhov wrote:
> On Tue, Oct 24, 2017 at 9:11 AM, Jason Gunthorpe
> <[email protected]> wrote:
> > On Tue, Oct 24, 2017 at 09:37:33PM +0530, PrasannaKumar Muralidharan wrote:
> >> Hi Jason,
> >>
> >> On 24 October 2017 at 21:25, Jason Gunthorpe
> >> <[email protected]> wrote:
> >> > On Tue, Oct 24, 2017 at 09:21:15PM +0530, PrasannaKumar Muralidharan wrote:
> >> >
> >> >> Please check the RFC [1]. It does use chip id. The rfc has issues and
> >> >> has to be fixed but still there could be users of the API.
> >> >>
> >> >> 1. https://www.spinics.net/lists/linux-crypto/msg28282.html
> >> >
> >> > That patch isn't safe at all. You need to store a kref to th chip in
> >> > the hwrng, not parse a string.
> >>
> >> The drivers/char/hw_random/tpm-rng.c module does not store the chip
> >> reference so I guess the usage is safe.
> >
> > It is using the default TPM, it is always safe to use the default tpm.
> 
> tpm-rng is abomination that should be kicked out as soon as possible.
> It wrecks havoc with the power management (TPM chip drivers may go
> into suspend state, but tpm_rng does not do any power management and
> happily forwards requests to suspended hardware) and may be available
> when there is no TPM at all yet (the drivers have not been probed yet,
> or have gotten a deferral, etc).
> 
> TPM core should register HWRNGs when chips are ready.
> 
> Thanks.
> 
> -- 
> Dmitry

I'm fine to review a two patch set where:

1. Patch 1 removes the existing TPM rng driver
2. Patch 2 makes the TPM driver as rng producer

Unrelate to patch that I'm proposing now but this sounds sensible.

/Jarkko