#5022 NORM Never A: OFW FAT FS confused by strange BPB

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#5022: OFW FAT FS confused by strange BPB
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 Reporter:  wmb at firmworks.com    |       Owner:  wmb at firmworks.com
     Type:  defect               |      Status:  new              
 Priority:  normal               |   Milestone:  Never Assigned   
Component:  ofw - open firmware  |     Version:                   
 Keywords:                       |    Verified:  0                
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 There is a USB key somewhere at 1cc that has a strange filesystem
 signature.  Specifically:

 a) The actual layout is FAT-16

 b) The partition type code says it is FAT-32 (OFW can handle that
 mismatch)

 c) The media type code in the BIOS Parameter Block says that it is a
 floppy disk.

 OFW assumes FAT12 for floppies, and thus misreads the filesystem.  The
 symptom is that you can list the directory with "dir u:\boot\", but you
 cannot actually read the data in the file "u:\boot\q2d04h.rom".

 The proper long-term fix would be to implement Microsoft's recommended
 FAT-size determination algorithm, which involves a complicated computation
 with various numbers in the BPB.  As a short-term fix, it is probably
 better to ignore the media type and thus not force FAT12 mode.

-- 
Ticket URL: <http://dev.laptop.org/ticket/5022>
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