Hi Sughosh,
On Mon, 4 Jul 2022 at 07:35, Sughosh Ganu <sughosh.g...@linaro.org> wrote:
>
> The TPM device comes with the random number generator(RNG)
> functionality which is built into the TPM device. Add logic to add the
> RNG child device in the TPM uclass post probe callback.
>
> The RNG device can then be used to pass a set of random bytes to the
> linux kernel, need for address space randomisation through the
> EFI_RNG_PROTOCOL interface.
>
> Signed-off-by: Sughosh Ganu <sughosh.g...@linaro.org>
> ---
> Changes since V5:
> * Check if the TPM RNG device has already been added, through a call
> to device_find_first_child_by_uclass()
>
> drivers/tpm/tpm-uclass.c | 37 +++++++++++++++++++++++++++++++++----
> 1 file changed, 33 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/tpm/tpm-uclass.c b/drivers/tpm/tpm-uclass.c
> index f67fe1019b..e1f1ef01e1 100644
> --- a/drivers/tpm/tpm-uclass.c
> +++ b/drivers/tpm/tpm-uclass.c
> @@ -11,10 +11,15 @@
> #include <log.h>
> #include <linux/delay.h>
> #include <linux/unaligned/be_byteshift.h>
> +#include <tpm_api.h>
> #include <tpm-v1.h>
> #include <tpm-v2.h>
> #include "tpm_internal.h"
>
> +#include <dm/lists.h>
> +
> +#define TPM_RNG_DRV_NAME "tpm-rng"
> +
> int tpm_open(struct udevice *dev)
> {
> struct tpm_ops *ops = tpm_get_ops(dev);
> @@ -136,12 +141,36 @@ int tpm_xfer(struct udevice *dev, const uint8_t
> *sendbuf, size_t send_size,
> return 0;
> }
>
> +static int tpm_uclass_post_probe(struct udevice *dev)
> +{
> + int ret;
> + const char *drv = TPM_RNG_DRV_NAME;
> + struct udevice *child;
> +
> + if (CONFIG_IS_ENABLED(TPM_RNG)) {
> + ret = device_find_first_child_by_uclass(dev, UCLASS_RNG,
> + &child);
> +
> + if (ret != -ENODEV) {
This may return -EIO (for example) in which case your log message is incorrect.
> + log_debug("RNG child already added to the TPM
> device\n");
> + return ret;
> + }
> +
> + ret = device_bind_driver(dev, drv, "tpm-rng0", &child);
> + if (ret)
> + return log_msg_ret("bind", ret);
> + }
> +
> + return 0;
> +}
> +
> UCLASS_DRIVER(tpm) = {
> - .id = UCLASS_TPM,
> - .name = "tpm",
> - .flags = DM_UC_FLAG_SEQ_ALIAS,
> + .id = UCLASS_TPM,
> + .name = "tpm",
> + .flags = DM_UC_FLAG_SEQ_ALIAS,
> #if CONFIG_IS_ENABLED(OF_REAL)
> - .post_bind = dm_scan_fdt_dev,
> + .post_bind = dm_scan_fdt_dev,
> #endif
> + .post_probe = tpm_uclass_post_probe,
> .per_device_auto = sizeof(struct tpm_chip_priv),
> };
> --
> 2.25.1
>
The driver needs a compatible string so it can be in the device tree.
Regards,
Simon
