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

[Simon Glass]

Hi Sugosh,

On Fri, 4 Mar 2022 at 06:35, Sughosh Ganu <sughosh.ganu at linaro.org> 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>
> Tested-by: Heinrich Schuchardt <xypron.glpk at 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) {

Devices are numbered by aliases, so you should use
uclass_get_device_by_seq() here.

>                 printf("No RNG device\n");
>                 return CMD_RET_FAILURE;
>         }
>
> -       if (argc >= 2)
> -               n = hextoul(argv[1], NULL);
> -
>         buf = malloc(n);

No need to malloc(), just set a limit for (say 64) bytes. See how
cmd_mem.c does it.

>         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
>

Regards,
Simon