[PATCH v1 1/3] drivers: add simple hw_random implementation
Sascha Hauer
s.hauer at pengutronix.de
Tue Mar 14 00:55:56 PDT 2017
On Mon, Mar 13, 2017 at 02:42:26PM +0100, Oleksij Rempel wrote:
> From: Steffen Trumtrar <s.trumtrar at pengutronix.de>
>
> 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 at pengutronix.de>
> Signed-off-by: Oleksij Rempel <o.rempel at pengutronix.de>
> ---
> drivers/Kconfig | 1 +
> drivers/Makefile | 1 +
> drivers/hw_random/Kconfig | 6 +++
> drivers/hw_random/Makefile | 1 +
> drivers/hw_random/core.c | 110 +++++++++++++++++++++++++++++++++++++++++++++
> include/linux/hw_random.h | 44 ++++++++++++++++++
> 6 files changed, 163 insertions(+)
> create mode 100644 drivers/hw_random/Kconfig
> create mode 100644 drivers/hw_random/Makefile
> create mode 100644 drivers/hw_random/core.c
> create mode 100644 include/linux/hw_random.h
>
> diff --git a/drivers/Kconfig b/drivers/Kconfig
> index cc086ac2d..2f5784a4d 100644
> --- a/drivers/Kconfig
> +++ b/drivers/Kconfig
> @@ -21,6 +21,7 @@ source "drivers/eeprom/Kconfig"
> source "drivers/input/Kconfig"
> source "drivers/watchdog/Kconfig"
> source "drivers/pwm/Kconfig"
> +source "drivers/hw_random/Kconfig"
> source "drivers/dma/Kconfig"
> source "drivers/gpio/Kconfig"
> source "drivers/w1/Kconfig"
> diff --git a/drivers/Makefile b/drivers/Makefile
> index 6a70f6ee1..7e9b80e59 100644
> --- a/drivers/Makefile
> +++ b/drivers/Makefile
> @@ -20,6 +20,7 @@ obj-y += misc/
> obj-y += dma/
> obj-y += watchdog/
> obj-y += gpio/
> +obj-$(CONFIG_HWRNG) += hw_random/
> obj-$(CONFIG_OFTREE) += of/
> obj-$(CONFIG_W1) += w1/
> obj-y += pinctrl/
> diff --git a/drivers/hw_random/Kconfig b/drivers/hw_random/Kconfig
> new file mode 100644
> index 000000000..807fcadd3
> --- /dev/null
> +++ b/drivers/hw_random/Kconfig
> @@ -0,0 +1,6 @@
> +menuconfig HWRNG
> + bool "HWRNG Support"
> + help
> + Support for HWRNG(Hardware Random Number Generator) devices.
> +
> + If unsure, say no.
> diff --git a/drivers/hw_random/Makefile b/drivers/hw_random/Makefile
> new file mode 100644
> index 000000000..15307b100
> --- /dev/null
> +++ b/drivers/hw_random/Makefile
> @@ -0,0 +1 @@
> +obj-$(CONFIG_HWRNG) += core.o
> diff --git a/drivers/hw_random/core.c b/drivers/hw_random/core.c
> new file mode 100644
> index 000000000..3bf464a8b
> --- /dev/null
> +++ b/drivers/hw_random/core.c
> @@ -0,0 +1,110 @@
> +/*
> + * Copyright (c) 2016 Pengutronix, Steffen Trumtrar <kernel at 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, u8 *buffer, size_t size, int wait)
u8 is not a nice type for a buffer. If the callers buffer is of another
type then we have an unnecessary cast. Use void * instead.
> +{
> + return rng->read(rng, buffer, size, wait);
> +}
> +
> +static int hwrng_init(struct hwrng *rng)
> +{
> + int ret = 0;
> +
> + if (rng->init) {
> + ret = rng->init(rng);
> + return ret;
> + }
> +
> + list_add_tail(&rng->list, &hwrngs);
When the new hwrng has an init function, Shouldn't it be added to the list
also?
> +
> + return 0;
> +}
> +
> +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;
> + }
Why the detour round rng->buf? Can't we copy to the destination buf
directly?
> +
> + 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)
> +{
> + rng->cdev.name = "hwrng";
> + 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);
> +
> + err = hwrng_init(rng);
> + if (err) {
> + free(rng->buf);
> + return err;
> + }
> +
> + rng->dev = dev;
> +
> + err = hwrng_register_cdev(rng);
> + if (err)
> + free(rng->buf);
> +
> + return err;
> +}
> diff --git a/include/linux/hw_random.h b/include/linux/hw_random.h
> new file mode 100644
> index 000000000..a115cc1fa
> --- /dev/null
> +++ b/include/linux/hw_random.h
> @@ -0,0 +1,44 @@
> +/*
> + Hardware Random Number Generator
> +
> + Please read Documentation/hw_random.txt for details on use.
> +
> + ----------------------------------------------------------
> + This software may be used and distributed according to the terms
> + of the GNU General Public License, incorporated herein by reference.
> +
> + */
> +
> +#ifndef LINUX_HWRANDOM_H_
> +#define LINUX_HWRANDOM_H_
> +
> +#include <linux/list.h>
> +
> +/**
> + * struct hwrng - Hardware Random Number Generator driver
> + * @name: Unique RNG name.
> + * @init: Initialization callback (can be NULL).
> + * @read: New API. drivers can fill up to max bytes of data
> + * into the buffer. The buffer is aligned for any type.
> + * @priv: Private data, for use by the RNG driver.
> + */
> +struct hwrng {
> + const char *name;
> + int (*init)(struct hwrng *rng);
> + int (*read)(struct hwrng *rng, void *data, size_t max, bool wait);
> + unsigned long priv;
This is unused and can be removed. The RNG driver should embed a struct
hwrng in it's driver private data and use container_of().
> + u8 *buf;
> +};
> +
> +/** Register a new Hardware Random Number Generator driver. */
> +extern int hwrng_register(struct device_d *dev, struct hwrng *rng);
> +extern struct hwrng *hwrng_get_first(void);
> +extern int hwrng_get_data(struct hwrng *rng, u8 *buffer, size_t size,
> + int wait);
Drop the 'extern's please.
Sascha
--
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