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