Re: [PATCH v2 5/6] tpm: add driver for cr50 on SPI

[Alexander Steffen]

On 18.07.2019 20:07, Stephen Boyd wrote:
> Quoting Alexander Steffen (2019-07-18 09:47:14)
> > On 17.07.2019 21:57, Stephen Boyd wrote:
> > > I think the idea is to let users override the quality if they decide
> > > that they don't want to use the default value specified in the driver.
> >
> > But isn't this something that applies to all TPMs, not only cr50? So
> > shouldn't this parameter be added to one of the global modules (tpm?
> > tpm_tis_core?) instead? Or do all low-level drivers (tpm_tis,
> > tpm_tis_spi, ...) need this parameter to provide a consistent interface
> > for the user?
>
> Looking at commit 7a64c5597aa4 ("tpm: Allow tpm_tis drivers to set hwrng
> quality.") I think all low-level drivers need to set the hwrng quality
> somehow. I'm not sure how tpm_tis_spi will do that in general, but at
> least for cr50 we have derived this quality number.
>
> I can move this module parameter to tpm_tis_core.c, but then it will be
> a global hwrng quality override for whatever tpm is registered through
> tpm_tis_core instead of per-tpm driver. This is sort of a problem right
> now too if we have two tpm_tis_spi devices. I can drop this parameter if
> you want.

Since it does not seem like a critical feature, maybe just drop it for 
now. Then we can figure out a way to do it properly and add it later.

Alexander