getbpb now returns 0 instead of S_DONE in case of an uninitialized
partition, copying the default BPB into the BPB.
The previous return of S_DONE in case of uninitialized partitions
resulted in rp->r_bpptr not getting set in bldbpb. This in
combination with indicating success resulted in garbage returned
via rp->r_bpptr.
The DPB values are now being set to the default BPB ones in media_check
ea951d8136/kernel/fatfs.c (L1728)
via call to bpb_to_dpb in case of an uninitialized partition.
This may have side effects. But because DF_NOACCESS is still set, I
think it is the right way to do it.
The commit also masks high bit of AL for INT25/26 containing the drive
number. Some programs may set the bit according to RBIL:
"examination of CPWIN386.CPL indicates that if this call fails with
error 0408h on an old-style (<32M) call, one should retry the
call with the high bit of the drive number in AL set"
Leaving the bit set may render the given drive number unusable.
It should do no harm to mask it to increase the chance of the operation
to succeed. Also, the AH should be set to zero, because drive is given
only in AL.
LBA_to_CHS() uses geometry taken from BIOS, but LBA_Transfer()
was using the geometry from VBR. This caused "count" variable
to underflow over unsigned long, then corrupting the entire
DOS memory with the large read.
This patch makes LBA_to_CHS() to return the geometry to caller,
so that the calculus do always match.
Thanks to @ecm-pushbx and @andrewbird for helping to
nail this down.
Based on lpproj's nec98:Fix for DOS 3.x partitions
5fab40fc63
On loading BPB check signature if extended fields (serial#, volume, and fstype) are available, use dummy values if not.
Return error if attempt to set BPB serial# and not part of BPB.
