Re: [PATCH v3 6/8] cmd: rng: Add support for selecting RNG device

[Ilias Apalodimas <ilias.apalodimas@linaro.org>]

On Fri, Mar 04, 2022 at 07:04:27PM +0530, 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@linaro.org>
> Tested-by: Heinrich Schuchardt <xypron.glpk@gmx.de>
> ---
> 
> Changes since V2: None
> 
>  cmd/rng.c | 31 +++++++++++++++++++++++--------
>  1 file changed, 23 insertions(+), 8 deletions(-)
> 
> diff --git a/cmd/rng.c b/cmd/rng.c
> index 1ad5a096c0..bb89cfa784 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"
> +	"  - 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
>  );
> -- 
> 2.25.1
> 
Reviewed-by: Ilias Apalodimas <ilias.apalodimas@linaro.org>