Re: [PATCH 3/3] tpm: Drop CONFIG_HW_RANDOM_TPM

[Mario Limonciello]

On 8/3/23 02:22, Paul Menzel wrote:
> Dear Mario,
>
>
> Thank you for the patch.
>
> Am 03.08.23 um 03:50 schrieb Mario Limonciello:
> > As the behavior of whether a TPM is registered for hwrng can be 
> > controlled
> > by command line, drop the kernel configuration option.
>
> Shouldn’t this be left in to be able to set the default without having 
> to change the Linux kernel command line?
It's the same thing as these commits:

b9b01a5625b5a ("random: use random.trust_{bootloader,cpu} command line 
option only")

d97c68d178fbf ("random: treat bootloader trust toggle the same way as 
cpu trust toggle")

So it matches the behavior of those.

> Kind regards
>
> Paul
>
>
> > Cc: Mateusz Schyboll <dragonn@xxxxx>
> > Signed-off-by: Mario Limonciello <mario.limonciello@xxxxxxx>
> > ---
> >   drivers/char/tpm/Kconfig    | 11 -----------
> >   drivers/char/tpm/tpm-chip.c |  6 +++---
> >   2 files changed, 3 insertions(+), 14 deletions(-)
> >
> > diff --git a/drivers/char/tpm/Kconfig b/drivers/char/tpm/Kconfig
> > index 927088b2c3d3f..69aaa730dc208 100644
> > --- a/drivers/char/tpm/Kconfig
> > +++ b/drivers/char/tpm/Kconfig
> > @@ -27,17 +27,6 @@ menuconfig TCG_TPM
> >   if TCG_TPM
> > -config HW_RANDOM_TPM
> > -    bool "TPM HW Random Number Generator support"
> > -    depends on TCG_TPM && HW_RANDOM && !(TCG_TPM=y && HW_RANDOM=m)
> > -    default y
> > -    help
> > -      This setting exposes the TPM's Random Number Generator as a hwrng
> > -      device. This allows the kernel to collect randomness from the 
> > TPM at
> > -      boot, and provides the TPM randomines in /dev/hwrng.
> > -
> > -      If unsure, say Y.
> > -
> >   config TCG_TIS_CORE
> >       tristate
> >       help
> > diff --git a/drivers/char/tpm/tpm-chip.c b/drivers/char/tpm/tpm-chip.c
> > index 8fb42232bd7a5..0d69335743469 100644
> > --- a/drivers/char/tpm/tpm-chip.c
> > +++ b/drivers/char/tpm/tpm-chip.c
> > @@ -533,7 +533,7 @@ static int tpm_add_hwrng(struct tpm_chip *chip)
> >       if (!trust_tpm)
> >           chip->flags |= TPM_CHIP_FLAG_HWRNG_DISABLED;
> > -    if (!IS_ENABLED(CONFIG_HW_RANDOM_TPM) || 
> > tpm_is_firmware_upgrade(chip) ||
> > +    if (tpm_is_firmware_upgrade(chip) ||
> >           chip->flags & TPM_CHIP_FLAG_HWRNG_DISABLED)
> >           return 0;
> > @@ -639,7 +639,7 @@ int tpm_chip_register(struct tpm_chip *chip)
> >       return 0;
> >   out_hwrng:
> > -    if (IS_ENABLED(CONFIG_HW_RANDOM_TPM) && 
> > !tpm_is_firmware_upgrade(chip) &&
> > +    if (!tpm_is_firmware_upgrade(chip) &&
> >           !(chip->flags & TPM_CHIP_FLAG_HWRNG_DISABLED))
> >           hwrng_unregister(&chip->hwrng);
> >   out_ppi:
> > @@ -665,7 +665,7 @@ EXPORT_SYMBOL_GPL(tpm_chip_register);
> >   void tpm_chip_unregister(struct tpm_chip *chip)
> >   {
> >       tpm_del_legacy_sysfs(chip);
> > -    if (IS_ENABLED(CONFIG_HW_RANDOM_TPM) && 
> > !tpm_is_firmware_upgrade(chip) &&
> > +    if (!tpm_is_firmware_upgrade(chip) &&
> >           !(chip->flags & TPM_CHIP_FLAG_HWRNG_DISABLED))
> >           hwrng_unregister(&chip->hwrng);
> >       tpm_bios_log_teardown(chip);