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[v8,4/8] tpm: Add the RNG child device

Message ID 20220722160209.863840-5-sughosh.ganu@linaro.org
State Accepted
Commit aedd45138ee61b4f5a48a2be9a358092a214edd5
Headers show
Series tpm: rng: Move TPM RNG functionality to driver model | expand

Commit Message

Sughosh Ganu July 22, 2022, 4:02 p.m. UTC 
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.

No compatible string is provided because this is not available in
the binding defined by Linux. If multiple rand devices are in the
system, then some method of selecting them (other than device tree)
will need to be used, or a binding will need to be added.

Signed-off-by: Sughosh Ganu <sughosh.ganu@linaro.org>
Reviewed-by: Ilias Apalodimas <ilias.apalodimas@linaro.org>
---
Changes since V7:
* Added a paragraph in the commit message highlighting the absence of
  the compatible string in the RNG driver, as suggested by Simon.
* Rearranged the inclusion of headers as per the coding style
  guidelines, as suggested by Simon.
* Use TPM_RNG_DRV_NAME for the RNG child name as suggested by Simon.

 drivers/tpm/tpm-uclass.c | 40 ++++++++++++++++++++++++++++++++++------
 1 file changed, 34 insertions(+), 6 deletions(-)
diff mbox series

Patch

diff --git a/drivers/tpm/tpm-uclass.c b/drivers/tpm/tpm-uclass.c
index f67fe1019b..0eb35f50c4 100644
--- a/drivers/tpm/tpm-uclass.c
+++ b/drivers/tpm/tpm-uclass.c
@@ -9,12 +9,16 @@ 
 #include <common.h>
 #include <dm.h>
 #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 <dm/lists.h>
+#include <linux/delay.h>
+#include <linux/unaligned/be_byteshift.h>
 #include "tpm_internal.h"
 
+#define TPM_RNG_DRV_NAME	"tpm-rng"
+
 int tpm_open(struct udevice *dev)
 {
 	struct tpm_ops *ops = tpm_get_ops(dev);
@@ -136,12 +140,36 @@  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) {
+			log_debug("RNG child already added to the TPM device\n");
+			return ret;
+		}
+
+		ret = device_bind_driver(dev, drv, TPM_RNG_DRV_NAME, &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),
 };