Re: [PATCH v7 2/7] tpm: rng: Add driver model interface for TPM RNG device

On Wed, 20 Jul 2022 at 15:30, Sughosh Ganu sughosh.ganu@linaro.org wrote:

The TPM device has a builtin random number generator(RNG) functionality. Expose the RNG functions of the TPM device to the driver model so that they can be used by the EFI_RNG_PROTOCOL if the protocol is installed.

Also change the function arguments and return type of the random number functions to comply with the driver model api.

Signed-off-by: Sughosh Ganu sughosh.ganu@linaro.org

Changes since V6:

• Remove the changes made in tpm-v[12].c to return -EIO instead of TPM_LIB_ERROR as suggested by Simon

drivers/rng/Kconfig | 9 +++++++++ drivers/rng/Makefile | 1 + drivers/rng/tpm_rng.c | 23 +++++++++++++++++++++++ lib/Kconfig | 1 + lib/tpm_api.c | 6 +++--- 5 files changed, 37 insertions(+), 3 deletions(-) create mode 100644 drivers/rng/tpm_rng.c

diff --git a/drivers/rng/Kconfig b/drivers/rng/Kconfig index 21a9ff0195..16143681da 100644 --- a/drivers/rng/Kconfig +++ b/drivers/rng/Kconfig @@ -74,4 +74,13 @@ config RNG_SMCCC_TRNG Enable random number generator for platforms that support Arm SMCCC TRNG interface.

+config TPM_RNG

•   bool "Enable random number generator on TPM device"
  

•   depends on TPM
  

•   default y
  

•   help
  

•     The TPM device has an inbuilt random number generator
  

•     functionality. Enable random number generator on TPM
  

•     devices.
  

endif

We could probably skip the extra Kconfig and just look for a TPM. But let's leave it as is for now, it's an easy change if we ever want that

diff --git a/drivers/rng/Makefile b/drivers/rng/Makefile index 2494717d7c..78f61051ac 100644 --- a/drivers/rng/Makefile +++ b/drivers/rng/Makefile @@ -13,3 +13,4 @@ obj-$(CONFIG_RNG_STM32MP1) += stm32mp1_rng.o obj-$(CONFIG_RNG_ROCKCHIP) += rockchip_rng.o obj-$(CONFIG_RNG_IPROC200) += iproc_rng200.o obj-$(CONFIG_RNG_SMCCC_TRNG) += smccc_trng.o +obj-$(CONFIG_TPM_RNG) += tpm_rng.o diff --git a/drivers/rng/tpm_rng.c b/drivers/rng/tpm_rng.c new file mode 100644 index 0000000000..1a5e9e2e4b --- /dev/null +++ b/drivers/rng/tpm_rng.c @@ -0,0 +1,23 @@ +// SPDX-License-Identifier: GPL-2.0-or-later +/*

• • Copyright (c) 2022, Linaro Limited
• */

+#include <dm.h> +#include <rng.h> +#include <tpm_api.h>

+static int rng_tpm_random_read(struct udevice *dev, void *data, size_t count) +{

•   return tpm_get_random(dev_get_parent(dev), data, count);
  

+}

+static const struct dm_rng_ops tpm_rng_ops = {

•   .read = rng_tpm_random_read,
  

+};

+U_BOOT_DRIVER(tpm_rng) = {

•   .name   = "tpm-rng",
  

•   .id     = UCLASS_RNG,
  

•   .ops    = &tpm_rng_ops,
  

+}; diff --git a/lib/Kconfig b/lib/Kconfig index 7dd777b56a..e888c29245 100644 --- a/lib/Kconfig +++ b/lib/Kconfig @@ -360,6 +360,7 @@ source lib/crypt/Kconfig config TPM bool "Trusted Platform Module (TPM) Support" depends on DM

•   imply DM_RNG
    help
      This enables support for TPMs which can be used to provide security
      features for your board. The TPM can be connected via LPC or I2C
  

diff --git a/lib/tpm_api.c b/lib/tpm_api.c index 4ac4612c81..032f383ca0 100644 --- a/lib/tpm_api.c +++ b/lib/tpm_api.c @@ -269,7 +269,7 @@ u32 tpm_get_random(struct udevice *dev, void *data, u32 count) if (tpm_is_v1(dev)) return tpm1_get_random(dev, data, count); else if (tpm_is_v2(dev))

•           return -ENOSYS; /* not implemented yet */
  

•   else
  

•           return -ENOSYS;
  

•           return tpm2_get_random(dev, data, count);
  

•   return -ENOSYS;
  

}

2.34.1

Reviewed-by: Ilias Apalodimas ilias.apalodimas@linaro.org