[PATCH 10/10] cmd: rng: Add support for selecting RNG device

[Heinrich Schuchardt]

On 2/24/22 19:05, Sughosh Ganu wrote:
> The 'rng' u-boot command is used for printing a select number of
> random bytes on the console. Currently, the RNG device from which the
> random bytes are read is fixed. However, a platform can have multiple
> RNG devices, one example being qemu, which has a virtio RNG device and
> the RNG pseudo device through the TPM chip.
>
> Extend the 'rng' command so that the user can provide the RNG device
> number from which the random bytes are to be read. This will be the
> device index under the RNG uclass.
>
> Signed-off-by: Sughosh Ganu <sughosh.ganu at linaro.org>
> ---
>   cmd/rng.c | 31 +++++++++++++++++++++++--------
>   1 file changed, 23 insertions(+), 8 deletions(-)
>
> diff --git a/cmd/rng.c b/cmd/rng.c
> index 1ad5a096c0..2b197e322e 100644
> --- a/cmd/rng.c
> +++ b/cmd/rng.c
> @@ -13,19 +13,34 @@
>
>   static int do_rng(struct cmd_tbl *cmdtp, int flag, int argc, char *const argv[])
>   {
> -	size_t n = 0x40;
> +	size_t n;
>   	struct udevice *dev;
>   	void *buf;
> +	int devnum;
>   	int ret = CMD_RET_SUCCESS;
>
> -	if (uclass_get_device(UCLASS_RNG, 0, &dev) || !dev) {
> +	switch (argc) {
> +	case 1:
> +		devnum = 0;
> +		n = 0x40;
> +		break;
> +	case 2:
> +		devnum = hextoul(argv[1], NULL);
> +		n = 0x40;
> +		break;
> +	case 3:
> +		devnum = hextoul(argv[1], NULL);
> +		n = hextoul(argv[2], NULL);
> +		break;
> +	default:
> +		return CMD_RET_USAGE;
> +	}
> +
> +	if (uclass_get_device(UCLASS_RNG, devnum, &dev) || !dev) {
>   		printf("No RNG device\n");
>   		return CMD_RET_FAILURE;
>   	}
>
> -	if (argc >= 2)
> -		n = hextoul(argv[1], NULL);
> -
>   	buf = malloc(n);
>   	if (!buf) {
>   		printf("Out of memory\n");
> @@ -46,12 +61,12 @@ static int do_rng(struct cmd_tbl *cmdtp, int flag, int argc, char *const argv[])
>
>   #ifdef CONFIG_SYS_LONGHELP
>   static char rng_help_text[] =
> -	"[n]\n"
> -	"  - print n random bytes\n";
> +	"[dev] [n]\n"

Thanks for updating the command.

I think this should be

     [dev [n]]

to indicate that dev takes precedence if only one parameter is provided.

A man-page doc/usage/rng.rst should be added in future.

Tested-by: Heinrich Schuchardt <xypron.glpk at gmx.de>


> +	"  - print n random bytes read from dev\n";
>   #endif
>
>   U_BOOT_CMD(
> -	rng, 2, 0, do_rng,
> +	rng, 3, 0, do_rng,
>   	"print bytes from the hardware random number generator",
>   	rng_help_text
>   );