Re: [PATCH v2 1/5] vvfat: introduce partitioned option

["Clément Chigot" <chigot@adacore.com>]

On Tue, Nov 11, 2025 at 8:43 AM Markus Armbruster <armbru@redhat.com> wrote:
>
> Kevin Wolf <kwolf@redhat.com> writes:
>
> > Am 10.11.2025 um 14:20 hat Markus Armbruster geschrieben:
> >> BALATON Zoltan <balaton@eik.bme.hu> writes:
> >>
> >> > On Mon, 10 Nov 2025, Clément Chigot wrote:
> >> >> On Mon, Nov 10, 2025 at 11:07 AM Markus Armbruster <armbru@redhat.com> wrote:
> >> >>>
> >> >>> Clément Chigot <chigot@adacore.com> writes:
> >> >>>
> >> >>>> This option tells whether a hard disk should be partitioned or not. It
> >> >>>> defaults to true and have the prime effect of preventing a master boot
> >> >>>> record (MBR) to be initialized.
> >> >>>>
> >> >>>> This is useful as some operating system (QNX, Rtems) don't
> >> >>>> recognized FAT mounted disks (especially SD cards) if a MBR is present.
> >> >>>>
> >> >>>> Signed-off-by: Clément Chigot <chigot@adacore.com>
>
> [...]
>
> >> >>> Not sure I like "partitioned".  Is a disk with an MBR and a partition
> >> >>> table contraining a single partition partitioned?  Call it "mbr"?
> >> >>
> >> >> It used to be called "mbr/no-mbr" but Kevin suggested renaming it in
> >> >> V1. Honestly I'm fine with both options:
> >> >> - Technically, the option prevents MBR which has a side effect for
> >> >> preventing partition tables
> >>
> >> Yes, because the partition table is part of the MBR.  I'd rather name
> >> the option after the entire thing it controls, not one of its parts.
> >>
> >> >> - Even it has a single partition, I think it makes sense to call a
> >> >> disk "partitioned" as long as it has a partition table
> >> >>
> >> >> But I'm not that familiar with disk formats, etc. I'll let you decide
> >> >> with Kevin, which one you prefer.
> >>
> >> Kevin is the maintainer, I just serve as advisor here.
> >
> > I figured that the meaning of "partitioned" is easier to understand for
> > a casual user than having or not having an MBR ("I don't want to boot
> > from this disk, why would I care about a boot record?").
>
> Fair point.
>
> Possible counter-points:
>
> * The default is almost always right for the casual user.  The
>   exception, as far as I understand, is certain guest OSes refuse to
>   play ball with certain devices when they have an MBR.
>
> * The configuration interface isn't exactly casual-user-friendly to
>   begin with.  @fat-type, what's that, and why do I care?  @floppy,
>   what's that, and why do I care?
>
> Anyway, you decide.

AFAICT, there are two open questions for that patch:

1. "mbr" vs "partitioned".
I do think "partitioned" is clearer, a bit more casual friendly. "mbr"
requires knowledge about FAT format, while what's a partition should
be known by a wider audience.
Side note, in V3, I'll remove the "unpartitioned" keyword to simply
replace it by "partitoned=false" (I wasn't aware such an obvious
possibility was working...). So we might even call it
"partition/partitions=true|false".

2. The default value. Should it be "false" for @floppy ?
IMO, having a default value independent of other arguments is always
better. Hence, I'll push for keeping "partitioned=true" as the
default, and having users forcing "partitioned=false" for floppy (an
error being raised otherwise). As we'll probably change the default
behavior with floppy anyway (cf patch 2), I don't think it will hurt a
lot to make users passing a new flag.

> > But if people think that "mbr" is better, that's fine with me.
> >
> > The only thing I really didn't want is the negative "no-mbr" and the
> > double negation in "no-mbr=off" that comes with it.
>
> Yes, negative names should definitely be avoided for boolean options.
>
> [...]
>