drivers: add simple hw_random implementation

Add a simple hw_random implementation based on code from
Linux v4.5-rc5.

All the entropypool initialization stuff is left out and
the obsolete data_read/data_present calls are omitted.

Signed-off-by: Steffen Trumtrar <s.trumtrar@pengutronix.de>
Signed-off-by: Oleksij Rempel <o.rempel@pengutronix.de>
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>

3 files changed, 132 insertions, 0 deletions

diff --git a/drivers/hw_random/Kconfig b/drivers/hw_random/Kconfig
new file mode 100644
index 0000000000..807fcadd31
--- /dev/null
+++ b/drivers/hw_random/Kconfig
@@ -0,0 +1,6 @@
+menuconfig HWRNG
+	bool "HWRNG Support"
+	help
+	  Support for HWRNG(Hardware Random Number Generator) devices.
+
+	  If unsure, say no.
diff --git a/drivers/hw_random/Makefile b/drivers/hw_random/Makefile
new file mode 100644
index 0000000000..15307b100f
--- /dev/null
+++ b/drivers/hw_random/Makefile
@@ -0,0 +1 @@
+obj-$(CONFIG_HWRNG)		+= core.o
diff --git a/drivers/hw_random/core.c b/drivers/hw_random/core.c
new file mode 100644
index 0000000000..ef2a988c76
--- /dev/null
+++ b/drivers/hw_random/core.c
@@ -0,0 +1,125 @@
+/*
+ * Copyright (c) 2016 Pengutronix, Steffen Trumtrar <kernel@pengutronix.de>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2
+ * as published by the Free Software Foundation.
+ *
+ * derived from Linux kernel drivers/char/hw_random/core.c
+ */
+
+#include <common.h>
+#include <linux/hw_random.h>
+#include <malloc.h>
+
+static LIST_HEAD(hwrngs);
+
+#define RNG_BUFFER_SIZE		32
+
+int hwrng_get_data(struct hwrng *rng, void *buffer, size_t size, int wait)
+{
+	return rng->read(rng, buffer, size, wait);
+}
+
+static int hwrng_init(struct hwrng *rng)
+{
+	int ret = 0;
+
+	if (rng->init)
+		ret = rng->init(rng);
+
+	if (!ret)
+		list_add_tail(&rng->list, &hwrngs);
+
+	return ret;
+}
+
+static ssize_t rng_dev_read(struct cdev *cdev, void *buf, size_t size,
+			    loff_t offset, unsigned long flags)
+{
+	struct hwrng *rng = container_of(cdev, struct hwrng, cdev);
+	size_t count = size;
+	ssize_t cur = 0;
+	int len;
+
+	memset(buf, 0, size);
+
+	while (count) {
+		int max = min(count, (size_t)RNG_BUFFER_SIZE);
+		len = hwrng_get_data(rng, rng->buf, max, true);
+		if (len < 0) {
+			cur = len;
+			break;
+		}
+
+		memcpy(buf + cur, rng->buf, len);
+
+		count -= len;
+		cur += len;
+	}
+
+	return cur;
+}
+
+static struct file_operations rng_chrdev_ops = {
+	.read  = rng_dev_read,
+	.lseek = dev_lseek_default,
+};
+
+static int hwrng_register_cdev(struct hwrng *rng)
+{
+	struct device_d *dev = rng->dev;
+	const char *alias;
+	char *devname;
+	int err;
+
+	alias = of_alias_get(dev->device_node);
+	if (alias) {
+		devname = xstrdup(alias);
+	} else {
+		err = cdev_find_free_index("hwrng");
+		if (err < 0) {
+			dev_err(dev, "no index found to name device\n");
+			return err;
+		}
+		devname = xasprintf("hwrng%d", err);
+	}
+
+	rng->cdev.name = devname;
+	rng->cdev.flags = DEVFS_IS_CHARACTER_DEV;
+	rng->cdev.ops = &rng_chrdev_ops;
+	rng->cdev.dev = rng->dev;
+
+	return devfs_create(&rng->cdev);
+}
+
+struct hwrng *hwrng_get_first(void)
+{
+	if (list_empty(&hwrngs))
+		return ERR_PTR(-ENODEV);
+	else
+		return list_first_entry(&hwrngs, struct hwrng, list);
+}
+
+int hwrng_register(struct device_d *dev, struct hwrng *rng)
+{
+	int err;
+
+	if (rng->name == NULL || rng->read == NULL)
+		return -EINVAL;
+
+	rng->buf = xzalloc(RNG_BUFFER_SIZE);
+	rng->dev = dev;
+
+	err = hwrng_init(rng);
+	if (err) {
+		free(rng->buf);
+		return err;
+	}
+
+	err = hwrng_register_cdev(rng);
+	if (err)
+		free(rng->buf);
+
+	return err;
+}