Re: [PATCH v6 5/7] cmd: rng: Use a statically allocated array for random bytes

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

On Mon, Jul 04, 2022 at 07:04:42PM +0530, Sughosh Ganu wrote:
> Use a statically allocated buffer on stack instead of using malloc for
> reading the random bytes. Using a local array is faster than
> allocating heap memory on every initiation of the command.
> 
> Signed-off-by: Sughosh Ganu <sughosh.ganu@linaro.org>
> ---
> Changes since V5: None
> 
>  cmd/rng.c | 17 +++++++----------
>  1 file changed, 7 insertions(+), 10 deletions(-)
> 
> diff --git a/cmd/rng.c b/cmd/rng.c
> index 2ddf27545f..81a23964b8 100644
> --- a/cmd/rng.c
> +++ b/cmd/rng.c
> @@ -14,9 +14,9 @@
>  static int do_rng(struct cmd_tbl *cmdtp, int flag, int argc, char *const argv[])
>  {
>  	size_t n;
> -	struct udevice *dev;
> -	void *buf;
> +	u8 buf[64];
>  	int devnum;
> +	struct udevice *dev;
>  	int ret = CMD_RET_SUCCESS;
>  
>  	switch (argc) {
> @@ -41,11 +41,10 @@ static int do_rng(struct cmd_tbl *cmdtp, int flag, int argc, char *const argv[])
>  		return CMD_RET_FAILURE;
>  	}
>  
> -	buf = malloc(n);
> -	if (!buf) {
> -		printf("Out of memory\n");
> -		return CMD_RET_FAILURE;
> -	}
> +	if (!n)
> +		return 0;
> +
> +	n = min(n, sizeof(buf));
>  
>  	if (dm_rng_read(dev, buf, n)) {
>  		printf("Reading RNG failed\n");
> @@ -54,15 +53,13 @@ static int do_rng(struct cmd_tbl *cmdtp, int flag, int argc, char *const argv[])
>  		print_hex_dump_bytes("", DUMP_PREFIX_OFFSET, buf, n);
>  	}
>  
> -	free(buf);
> -
>  	return ret;
>  }
>  
>  #ifdef CONFIG_SYS_LONGHELP
>  static char rng_help_text[] =
>  	"[dev [n]]\n"
> -	"  - print n random bytes read from dev\n";
> +	"  - print n random bytes(max 64) read from dev\n";
>  #endif
>  
>  U_BOOT_CMD(
> -- 
> 2.25.1
> 

Reviewed-by: Ilias Apalodimas <ilias.apalodimas@linaro.org>