[PATCH] cmd: part: number: remove inconsistent 0x from returned value

[Simon Glass]

Hi Stefan,

On Thu, 11 Mar 2021 at 23:58, Stefan Herbrechtsmeier
<stefan.herbrechtsmeier-oss at weidmueller.com> wrote:
>
> Hi Simon,
>
> Am 12.03.2021 um 05:45 schrieb Simon Glass:
> > Hi Stefan,
> >
> > On Mon, 8 Mar 2021 at 03:45, Stefan Herbrechtsmeier
> > <stefan.herbrechtsmeier-oss at weidmueller.com> wrote:
> >>
> >> Hi,
> >>
> >> Am 06.03.2021 um 21:12 schrieb Tom Rini:
> >>> On Fri, Mar 05, 2021 at 07:35:24AM -0700, Simon Glass wrote:
> >>>> Hi,
> >>>>
> >>>> On Fri, 5 Mar 2021 at 07:33, Stefan Herbrechtsmeier
> >>>> <stefan.herbrechtsmeier-oss at weidmueller.com> wrote:
> >>>>>
> >>>>> Hi Eugeniu,
> >>>>>
> >>>>> Am 05.03.2021 um 12:52 schrieb Eugeniu Rosca:
> >>>>>> Hello Stefan,
> >>>>>>
> >>>>>> On Fri, Mar 05, 2021 at 07:39:04AM +0000, Stefan Herbrechtsmeier wrote:
> >>>>>>> From: Stefan Herbrechtsmeier <stefan.herbrechtsmeier at weidmueller.com>
> >>>>>>>
> >>>>>>> The part number sub-command returns the hexadecimal value with a leading
> >>>>>>> 0x.
> >>>>>>
> >>>>>> That's to make sure that:
> >>>>>>       - users have clear and unequivocal feedback that '10'
> >>>>>>         returned by the command is really HEX 10, not DEC 10.
> >>>>>>       - other U-Boot commands which need to take '0x10' as input
> >>>>>>         will interpret it correctly, regardless of the way these
> >>>>>>         other commands implement ascii-to-integer conversion.
> >>>>>
> >>>>> 'Almost all U-Boot commands expect numbers to be entered in hexadecimal
> >>>>> input format.' [1]
> >>>>>
> >>>>> The filesystem commands use `simple_strtoul(.., 16)` and interpret the
> >>>>> value as hexadecimal value.
> >>>>>
> >>>>> The 0x suggests that a 10 will be interpreted as decimal value and this
> >>>>> isn't true.
> >>>>>
> >>>>>>> This is inconsistent with other values in the command
> >>>>>>
> >>>>>> It could be, but it is then better to fix the inconsistency in those
> >>>>>> commands/sub-commands which add the ambiguity.
> >>>>>
> >>>>> Normally you are right but U-Boot by design use hexadecimal values
> >>>>> without 0x. The env_set_hex functions doesn't use 0x.
> >>>>>
> >>>>>>> and U-Boot uses hexadecimal values generally.
> >>>>>>
> >>>>>> The key word is "generally", but not always. Some U-Boot commands will
> >>>>>> process '10' as HEX 10 and some will process 10 as DEC 10. So, in order
> >>>>>> to avoid these games, I vote for leaving the 0x in place.
> >>>>
> >>>> I would be very surprised if 10 means 0d10 in a partition number. I
> >>>> agree that putting a 0x in these values is a dangerous precedent and
> >>>> will just cause confusion. U-Boot uses hex for addresses and most
> >>>> arguments
> >>>>
> >>>>>
> >>>>> You can avoid it only if you could mark decimal numbers and that is
> >>>>> impossible.
> >>>>
> >>>> 0d10 is available. People are not used to it though.
> >>>>
> >>>> Reviewed-by: Simon Glass <sjg at chromium.org>
> >>>>
> >>>>>
> >>>>> @Tom: Does U-Boot still expect numbers to be hexadecimal values?
> >>>>>
> >>>>> [1] https://www.denx.de/wiki/DULG/UBootCommandLineInterface
> >>>>>
> >>>>>>>
> >>>>>>> Signed-off-by: Stefan Herbrechtsmeier <stefan.herbrechtsmeier at weidmueller.com>
> >>>>>>>
> >>>>>>> ---
> >>>>>>>
> >>>>>>>     cmd/part.c | 2 +-
> >>>>>>>     1 file changed, 1 insertion(+), 1 deletion(-)
> >>>>>>>
> >>>>>>> diff --git a/cmd/part.c b/cmd/part.c
> >>>>>>> index 3395c17b89..56e1852c66 100644
> >>>>>>> --- a/cmd/part.c
> >>>>>>> +++ b/cmd/part.c
> >>>>>>> @@ -152,7 +152,7 @@ static int do_part_info(int argc, char *const argv[], enum cmd_part_info param)
> >>>>>>>                snprintf(buf, sizeof(buf), LBAF, info.size);
> >>>>>>>                break;
> >>>>>>>        case CMD_PART_INFO_NUMBER:
> >>>>>>> -            snprintf(buf, sizeof(buf), "0x%x", part);
> >>>>>>> +            snprintf(buf, sizeof(buf), "%x", part);
> >>>>>>
> >>>
> >>> I am not a fan of this change as well, especially having spent time on
> >>> some platforms that have literally 20+ partition entries.  Being clear
> >>> here that this is a hex value is important.
> >>
> >> But isn't it confusing to use a 0x for a value which is treated as
> >> hexadecimal value by the commands independent of the 0x. The 0x results
> >> in the assumption that the partition is a decimal value without the 0x.
> >>
> >> What is the correct way to convert a hexadecimal value into a decimal
> >> value on the shell? I need a value without prefix (decimal value) to
> >> pass it to the root parameter of the bootargs.
> >>
> >> At the moment the different default numeral systems of common functions
> >> like load and test are very irritating. The load command uses
> >> hexadecimal value and doesn't support decimal value. The test command
> >> uses decimal value by default but supports hexadecimal values with a
> >> prefix. This means that the returned variable filesize of the command
> >> load couldn't be checked by test and the user have to use the itest command.
> >
> > Let's use hex where possible. I am not sure what to do with the test
> > command, nor how often we use 'test' with addresses, but I think
> > adding an option to 'test' to make it use hex or dec would be good.
>
> But what is the difference to test vs itest?

Well at present test uses decimal by default, unfortunately.

>
> > Then one day we could change the default to hex.
>
> Is this possible? This would be a breaking change.

I'll see if I can do a patch.

>
> I think the main problem is the unclear default numeral system. It would
> be much easy if every number without a prefix have the same numeral
> system. This would mean that a `simple_strtoul(.., 0)` would fall back
> to the default numeral system if the value hasn't any prefix (0x or 0d).
> At the moment `simple_strtoul(.., 0)` fall back to decimal and many
> commands use different numeral systems (`simple_strtoul(.., 10)` or
> `simple_strtoul(.., 16)`).

Yes, that seems right to me. The '0' should default to hex.

>
> Independent of this problem I need a command to convert a value to
> decimal without any prefix. Can you recommend any command or should I
> add a printf command?

I don't know of any, so a way to snprintf into an env var seems useful.

Regards,
Simon