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

Patrick DELAUNAY
2019-12-16T12:30:35Z

Hi,

> From: U-Boot <u-boot-bounces@lists.denx.de> On Behalf Of Sughosh Ganu
> Sent: vendredi 13 dÃ©cembre 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