Clément Chigot <[email protected]> writes:
> On Mon, Nov 10, 2025 at 2:09 PM Markus Armbruster <[email protected]> wrote:
>>
>> Clément Chigot <[email protected]> writes:
>>
>> > On Mon, Nov 10, 2025 at 11:13 AM Markus Armbruster <[email protected]>
>> > wrote:
>> >>
>> >> Clément Chigot <[email protected]> writes:
>> >>
>> >> > This allows more flexibility to vvfat backend. The values of "Number of
>> >> > Heads" and "Sectors per track" are based on SD specifications Part 2.
>> >> >
>> >> > Due to the FAT architecture, not all sizes are reachable. Therefore, it
>> >> > could be round up to the closest available size.
>> >> >
>> >> > FAT32 has not been adjusted and thus still default to 504 Mib.
>> >> >
>> >> > For floppy, only 1440 Kib and 2880 Kib are supported.
>> >> >
>> >> > Signed-off-by: Clément Chigot <[email protected]>
>> >>
>> >> [...]
>> >>
>> >> > diff --git a/qapi/block-core.json b/qapi/block-core.json
>> >> > index 8a479ba090..0bcb360320 100644
>> >> > --- a/qapi/block-core.json
>> >> > +++ b/qapi/block-core.json
>> >> > @@ -3478,11 +3478,17 @@
>> >> > # (default: true)
>> >> > # (since 10.2)
>> >> > #
>> >> > +# @fat-size: size of the device in bytes. Due to FAT underlying
>> >> > +# architecture, this size can be rounded up to the closest valid
>> >> > +# size.
>> >> > +# (since 10.2)
>> >> > +#
>> >>
>> >> Can you explain again why you moved from @size to @fat-size?
>> >
>> > Just to be sure, you mean in the above comment, in the commit message or
>> > both ?
>>
>> Just to me, because I'm not sure I like the change, but that may well be
>> due to a lack of understanding of your reasons.
>
> Naming `fat-size` instead of `size` ensures the parameter is only
> recognized by the vvfat backend. In particular, it will be refused by
> the default raw format, avoiding confusion:
> "-drive file=fat:<path>,size=256M" results in a 504M FAT disk
> truncated to 256M, raw format being implicit.
> "-drive file=fat:<path>,fat-size=256M" is refused. "fat-size" is
> unsupported by raw format.
I figure throwing in format=raw to make raw format explicit doesn't
change anything. Correct?
> "-drive file=fat:<path>,format=vvfat,fat-size=256M" results in a 256M FAT
> disk.
> "-drive file=fat:<path>,format=vvfat,size=256M" is refused. "size" is
> unsupported by vvfat format.
If it was called @size, what behavior would we get? Just two cases, I
think:
1. With raw format:
-drive file=fat:<path>,size=256M
2. Without raw format:
-drive file=fat:<path>,format=vvfat,size=256M
