[PATCH v3] i2c_tools.c: add i2ctransfer utility

[Denys Vlasenko]

On Mon, Jan 7, 2019 at 2:29 PM Nikolaus Voss <nv at vosn.de> wrote:
> i2ctransfer sends and receives user defined i2c messages
>
> v2: apply Xabier's comments: add -a option, don't decrement argc,
>     use bb_show_usage() and xzalloc()
> v3: fix possible out of bound access to msgs[nmsgs]
>
> Reviewed-by: Xabier Oneca -- xOneca <xoneca at gmail.com>
> Signed-off-by: Nikolaus Voss <nikolaus.voss at loewensteinmedical.de>
> ---
>  miscutils/i2c_tools.c | 206 +++++++++++++++++++++++++++++++++++++++++-
>  1 file changed, 205 insertions(+), 1 deletion(-)
>
> +                       switch (*arg_ptr++) {
> +                       case 'r': flags |= I2C_M_RD; break;
> +                       case 'w': break;
> +                       default:
> +                               bb_show_usage();
> +                       }
> +
> +                       len = strtoul(arg_ptr, &end, 0);
> +                       if (len > 0xffff || arg_ptr == end)
> +                               bb_error_msg_and_die("Error: Length invalid: %s\n", *argv);
> +
> +                       arg_ptr = end;
> +                       if (*arg_ptr) {
> +                               if (*arg_ptr++ != '@')
> +                                       bb_error_msg_and_die("Error: Unknown separator after length: %s\n",
> +                                                    *argv);
> +                               bus_addr = xstrtou_range(arg_ptr, 0, first, last);
> +
> +                               if (!(opts & opt_f))
> +                                       i2c_set_slave_addr(fd, bus_addr, opts & opt_f);

This last if() looks fishy. What is it trying to accomplish?