Re: [PATCH] fdc: fix floppy boot for Red Hat Linux 5.2

2021-03-12 Thread John Snow 

On 3/12/21 3:01 AM, Thomas Huth wrote:


That whole table-based approach seems quite unreliable to me - I've seen 
floppy disks with 80, 81, 82 or sometimes even 83 tracks in the past, so 
I think we would do better with a more flexible way of guessing ... but 
for the time being, this is certainly a quick and easy fix that also 
should not have any negative impact, thus:


Reviewed-by: Thomas Huth 


Yes, that's my thought. I can't personally justify tackling this hokey 
system -- I simply don't know enough about the history of the device to 
design a suitable replacement.


So, it's a band-aid, but one that fits with the way the floppy has 
worked for quite a long time, and seems the least likely to bother 
anything further.


--js

Re: [PATCH] fdc: fix floppy boot for Red Hat Linux 5.2

2021-03-12 Thread Thomas Huth 

On 12/03/2021 07.32, John Snow wrote:

The image size indicates it's an 81 track floppy disk image, which we
don't have a listing for in the geometry table. When you force the drive
type to 1.44MB, it guesses the reasonably close 18/80. When the drive
type is allowed to auto-detect or set to 2.88, it guesses a very
incorrect geometry.

auto, 144 and 288 drive types get the right geometry with the new entry
in the table.

Reported-by: Michael Tokarev 
Signed-off-by: John Snow 
---
  hw/block/fdc.c | 1 +
  1 file changed, 1 insertion(+)

diff --git a/hw/block/fdc.c b/hw/block/fdc.c
index 198940e737..b2f26ba587 100644
--- a/hw/block/fdc.c
+++ b/hw/block/fdc.c
@@ -122,6 +122,7 @@ static const FDFormat fd_formats[] = {
  /* First entry is default format */
  /* 1.44 MB 3"1/2 floppy disks */
  { FLOPPY_DRIVE_TYPE_144, 18, 80, 1, FDRIVE_RATE_500K, }, /* 3.5" 2880 */
+{ FLOPPY_DRIVE_TYPE_144, 18, 81, 1, FDRIVE_RATE_500K, },
  { FLOPPY_DRIVE_TYPE_144, 20, 80, 1, FDRIVE_RATE_500K, }, /* 3.5" 3200 */
  { FLOPPY_DRIVE_TYPE_144, 21, 80, 1, FDRIVE_RATE_500K, },
  { FLOPPY_DRIVE_TYPE_144, 21, 82, 1, FDRIVE_RATE_500K, },


That whole table-based approach seems quite unreliable to me - I've seen 
floppy disks with 80, 81, 82 or sometimes even 83 tracks in the past, so I 
think we would do better with a more flexible way of guessing ... but for 
the time being, this is certainly a quick and easy fix that also should not 
have any negative impact, thus:


Reviewed-by: Thomas Huth