[PATCH v3 5/8] sandbox: rng: Add a random number generator(rng) driver

[Patrick DELAUNAY <patrick.delaunay@st.com>]

Hi,

> From: U-Boot <u-boot-bounces@lists.denx.de> On Behalf Of Sughosh Ganu
> Sent: vendredi 13 décembre 2019 08:14
> 
> Add a sandbox driver for random number generation. Mostly aimed at providing a
> unit test for rng uclass.
> 
> Signed-off-by: Sughosh Ganu <sughosh.ganu@linaro.org>
> Reviewed-by: Patrice Chotard <patrice.chotard@st.com>
> ---
>  arch/sandbox/dts/test.dts |  4 ++++
>  drivers/rng/Kconfig       |  7 +++++++
>  drivers/rng/Makefile      |  1 +
>  drivers/rng/sandbox_rng.c | 36 ++++++++++++++++++++++++++++++++++++
>  4 files changed, 48 insertions(+)
>  create mode 100644 drivers/rng/sandbox_rng.c
> 
> diff --git a/arch/sandbox/dts/test.dts b/arch/sandbox/dts/test.dts index
> fdb08f2..2c85540 100644
> --- a/arch/sandbox/dts/test.dts
> +++ b/arch/sandbox/dts/test.dts
> @@ -599,6 +599,10 @@
>  		reset-names = "other", "test";
>  	};
> 
> +	rng at 0 {
> +		compatible = "sandbox,sandbox-rng";
> +	};
> +
>  	rproc_1: rproc at 1 {
>  		compatible = "sandbox,test-processor";
>  		remoteproc-name = "remoteproc-test-dev1"; diff --git
> a/drivers/rng/Kconfig b/drivers/rng/Kconfig index 5fc11db..3a1d3f0 100644
> --- a/drivers/rng/Kconfig
> +++ b/drivers/rng/Kconfig
> @@ -6,6 +6,13 @@ config DM_RNG
>  	  This interface is used to initialise the rng device and to
>  	  read the random seed from the device.
> 
> +config RNG_SANDBOX
> +       bool "Sandbox random number generator"
> +       depends on SANDBOX && DM_RNG
> +       help
> +         Enable random number generator for sandbox. This is an
> +	 emulation of a rng device.
> +
>  config RNG_STM32MP1
>         bool "Enable random number generator for STM32MP1"
>         depends on ARCH_STM32MP && DM_RNG diff --git a/drivers/rng/Makefile
> b/drivers/rng/Makefile index 699beb3..3517005 100644
> --- a/drivers/rng/Makefile
> +++ b/drivers/rng/Makefile
> @@ -4,4 +4,5 @@
>  #
> 
>  obj-$(CONFIG_DM_RNG) += rng-uclass.o
> +obj-$(CONFIG_RNG_SANDBOX) += sandbox_rng.o
>  obj-$(CONFIG_RNG_STM32MP1) += stm32mp1_rng.o diff --git
> a/drivers/rng/sandbox_rng.c b/drivers/rng/sandbox_rng.c new file mode 100644
> index 0000000..c5be552
> --- /dev/null
> +++ b/drivers/rng/sandbox_rng.c
> @@ -0,0 +1,36 @@
> +// SPDX-License-Identifier: GPL-2.0-or-later
> +/*
> + * Copyright (c) 2019, Linaro Limited
> + */
> +
> +#include <common.h>
> +#include <dm.h>
> +#include <rng.h>
> +
> +static unsigned long random = 0xdeadbeef;
> +
> +static int sandbox_rng_read(struct udevice *dev, void *data, size_t
> +len) {

Add protection on length  I think: 
	If (len != sizeof(random))
		retrun - EINVAL;

or treat the case len > 4 with loop ?

> +	random ^= ~0UL;
> +	*(unsigned long *)data = random;
> +
> +	return sizeof(random);

Read is OK, so I think the correct return value is 0:

	return 0;

NB: result (int) can be not enough to return the value read (size_t)

PS: it not really a random generator here but simple sequence
       0xdeadbeef -> 0x21524110 -> 0xdeadbeef

      It is enough for unitary test, but is is enough for sandbox ?
      we could reused PRNG code from lib/rand.c ?

> +}
> +
> +static const struct dm_rng_ops sandbox_rng_ops = {
> +	.read = sandbox_rng_read,
> +};
> +
> +static const struct udevice_id sandbox_rng_match[] = {
> +	{
> +		.compatible = "sandbox,sandbox-rng",
> +	},
> +	{},
> +};
> +
> +U_BOOT_DRIVER(sandbox_rng) = {
> +	.name = "sandbox-rng",
> +	.id = UCLASS_RNG,
> +	.of_match = sandbox_rng_match,
> +	.ops = &sandbox_rng_ops,
> +};
> --
> 2.7.4