Re: [PATCH] fix floppy for PAGE_SIZE != 4KB

[Jens Axboe <axboe@kernel.dk>]

On 11/14/25 9:25 AM, Ren? Rebe wrote:
> From: Jens Axboe <axboe@kernel.dk>
> 
>> On 11/14/25 6:41 AM, Rene Rebe wrote:
>>> For years I wondered why the floppy driver does not just work on
>>> sparc64, e.g:
>>>
>>> root@SUNW_375_0066:# disktype /dev/fd0
>>> --- /dev/fd0
>>> disktype: Can't open /dev/fd0: No such device or address
>>>
>>> [  525.341906] disktype: attempt to access beyond end of device
>>>                fd0: rw=0, sector=0, nr_sectors = 16 limit=8
>>> [  525.341991] floppy: error 10 while reading block 0
>>>
>>> Turns out floppy.c __floppy_read_block_0 tries to read one page for
>>> the first test read to determine the disk size and thus fails if that
>>> is greater than 4k. Adjust minimum MAX_DISK_SIZE to PAGE_SIZE to fix
>>> floppy on sparc64 and likely all other PAGE_SIZE != 4KB configs.
>>
>> 16k seem like a lot to read from a floppy, no? Why isn't it just
>> reading a single 512b sector? Or just cap it at 4k rather than do
>> a full page, at least?
> 
> Well, on my sparc64.config it is just 8k and I did not feel like
> changing this vintage code more than was necessiary to write a floppy
> for a Firmware update of another systems while my Ultra10 was the only
> system with a floppy drive in my office. But even 16k or 64k is not
> that much of a 1.44mb disk.

64k is 4% of a floppy disk! But I hear you, works for you.

> But if someone wants to refactor this code some more, ... I'm happy to
> test it, too ;-)

I don't think refactoring would be required here, it's probably just
capping that probe read to something constant irrespective of hardware
page sizes.

-- 
Jens Axboe