dm: rng: Add random number generator(rng) uclass

Add a uclass for reading a random number seed from a random number
generator device.

Signed-off-by: Sughosh Ganu <sughosh.ganu@linaro.org>
Reviewed-by: Patrice Chotard <patrice.chotard@st.com>
Reviewed-by: Heinrich Schuchardt <xypron.glpk@gmx.de>
Reviewed-by: Simon Glass <sjg@chromium.org>

drivers/Kconfig

@@ -90,6 +90,8 @@ source "drivers/remoteproc/Kconfig"
 
 source "drivers/reset/Kconfig"
 
+source "drivers/rng/Kconfig"
+
 source "drivers/rtc/Kconfig"
 
 source "drivers/scsi/Kconfig"

drivers/Makefile

@@ -116,4 +116,5 @@ obj-$(CONFIG_W1_EEPROM) += w1-eeprom/
 
 obj-$(CONFIG_MACH_PIC32) += ddr/microchip/
 obj-$(CONFIG_DM_HWSPINLOCK) += hwspinlock/
+obj-$(CONFIG_DM_RNG) += rng/
 endif

drivers/rng/Kconfig

@@ -0,0 +1,7 @@
+config DM_RNG
+	bool "Driver support for Random Number Generator devices"
+	depends on DM
+	help
+	  Enable driver model for random number generator(rng) devices.
+	  This interface is used to initialise the rng device and to
+	  read the random seed from the device.

drivers/rng/Makefile

@@ -0,0 +1,6 @@
+# SPDX-License-Identifier: GPL-2.0+
+#
+# Copyright (c) 2019, Linaro Limited
+#
+
+obj-$(CONFIG_DM_RNG) += rng-uclass.o

drivers/rng/rng-uclass.c

@@ -0,0 +1,23 @@
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * Copyright (c) 2019, Linaro Limited
+ */
+
+#include <common.h>
+#include <dm.h>
+#include <rng.h>
+
+int dm_rng_read(struct udevice *dev, void *buffer, size_t size)
+{
+	const struct dm_rng_ops *ops = device_get_ops(dev);
+
+	if (!ops->read)
+		return -ENOSYS;
+
+	return ops->read(dev, buffer, size);
+}
+
+UCLASS_DRIVER(rng) = {
+	.name = "rng",
+	.id = UCLASS_RNG,
+};