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floppy: support arbitrary first-sector numbers 

The current floppy_struct allows floppies to number sectors starting
from 0 or 1.  This patch allows arbitrary first-sector numbers - for
example, 0xC1 for Amstrad CPC disks.

This extends the existing 1-bit field (FD_ZEROBASED, bit 2 of stretch)
to 8 bits (FD_SECTMASK, bits 2 to 9).

Currently 0x00 denotes a first sector number of 1, and 0x01 denotes a
first sector number of 0.  We extend this by interpreting FD_SECTMASK
as the first sector number with the LSB flipped.

Signed-off-by: Keith Wansbrough <keith@lochan.org>
Cc: Alain Knaff <alain@linux.lu>
Cc: Michael Kerrisk <mtk.manpages@googlemail.com>
Cc: Karel Zak <kzak@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
This commit is contained in:
Keith Wansbrough 2008-09-22 14:57:17 -07:00 committed by Jens Axboe
parent 061837bc86
commit 9e49184c82
2 changed files with 22 additions and 9 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

23
drivers/block/floppy.c
View File

@ -423,8 +423,15 @@ static struct floppy_raw_cmd *raw_cmd, default_raw_cmd;
* 1581's logical side 0 is on physical side 1, whereas the Sharp's logical
* side 0 is on physical side 0 (but with the misnamed sector IDs).
* 'stretch' should probably be renamed to something more general, like
* 'options'. Other parameters should be self-explanatory (see also
* setfdprm(8)).
* 'options'.
*
* Bits 2 through 9 of 'stretch' tell the number of the first sector.
* The LSB (bit 2) is flipped. For most disks, the first sector
* is 1 (represented by 0x00<<2). For some CP/M and music sampler
* disks (such as Ensoniq EPS 16plus) it is 0 (represented as 0x01<<2).
* For Amstrad CPC disks it is 0xC1 (represented as 0xC0<<2).
*
* Other parameters should be self-explanatory (see also setfdprm(8)).
*/
/*
Size
@ -2236,9 +2243,9 @@ static void setup_format_params(int track)
}
}
}
if (_floppy->stretch & FD_ZEROBASED) {
if (_floppy->stretch & FD_SECTBASEMASK) {
for (count = 0; count < F_SECT_PER_TRACK; count++)
here[count].sect--;
here[count].sect += FD_SECTBASE(_floppy) - 1;
}
}
@ -2649,7 +2656,7 @@ static int make_raw_rw_request(void)
}
HEAD = fsector_t / _floppy->sect;
if (((_floppy->stretch & (FD_SWAPSIDES | FD_ZEROBASED)) ||
if (((_floppy->stretch & (FD_SWAPSIDES | FD_SECTBASEMASK)) ||
TESTF(FD_NEED_TWADDLE)) && fsector_t < _floppy->sect)
max_sector = _floppy->sect;
@ -2679,7 +2686,7 @@ static int make_raw_rw_request(void)
CODE2SIZE;
SECT_PER_TRACK = _floppy->sect << 2 >> SIZECODE;
SECTOR = ((fsector_t % _floppy->sect) << 2 >> SIZECODE) +
((_floppy->stretch & FD_ZEROBASED) ? 0 : 1);
FD_SECTBASE(_floppy);
/* tracksize describes the size which can be filled up with sectors
* of size ssize.
@ -3311,7 +3318,7 @@ static inline int set_geometry(unsigned int cmd, struct floppy_struct *g,
g->head <= 0 ||
g->track <= 0 || g->track > UDP->tracks >> STRETCH(g) ||
/* check if reserved bits are set */
(g->stretch & ~(FD_STRETCH | FD_SWAPSIDES | FD_ZEROBASED)) != 0)
(g->stretch & ~(FD_STRETCH | FD_SWAPSIDES | FD_SECTBASEMASK)) != 0)
return -EINVAL;
if (type) {
if (!capable(CAP_SYS_ADMIN))
@ -3356,7 +3363,7 @@ static inline int set_geometry(unsigned int cmd, struct floppy_struct *g,
if (DRS->maxblock > user_params[drive].sect ||
DRS->maxtrack ||
((user_params[drive].sect ^ oldStretch) &
(FD_SWAPSIDES | FD_ZEROBASED)))
(FD_SWAPSIDES | FD_SECTBASEMASK)))
invalidate_drive(bdev);
else
process_fd_request();

8
include/linux/fd.h
View File

@ -15,10 +15,16 @@ struct floppy_struct {
sect, /* sectors per track */
head, /* nr of heads */
track, /* nr of tracks */
stretch; /* !=0 means double track steps */
stretch; /* bit 0 !=0 means double track steps */
/* bit 1 != 0 means swap sides */
/* bits 2..9 give the first sector */
/* number (the LSB is flipped) */
#define FD_STRETCH 1
#define FD_SWAPSIDES 2
#define FD_ZEROBASED 4
#define FD_SECTBASEMASK 0x3FC
#define FD_MKSECTBASE(s) (((s) ^ 1) << 2)
#define FD_SECTBASE(floppy) ((((floppy)->stretch & FD_SECTBASEMASK) >> 2) ^ 1)
unsigned char gap, /* gap1 size */