[PATCH v7 5/7] cmd: rng: Use a statically allocated array for random bytes

[Sughosh Ganu]

hi Ilias,

On Thu, 21 Jul 2022 at 13:36, Ilias Apalodimas
<ilias.apalodimas at linaro.org> wrote:
>
> Hi Sughosh,
>
> This is missing the r-b tags from Simon and myself.  Once I finish up
> the review, can you re-send the series with the missing tags?

Sure, will add the r-b tags in the next version. Thanks.

-sughosh

>
> Thanks
> /Ilias
>
> On Wed, 20 Jul 2022 at 15:30, Sughosh Ganu <sughosh.ganu at linaro.org> 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 at linaro.org>
> > ---
> > Changes since V6: 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(
> > --
> > 2.34.1
> >