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Commit 9e49184c authored by Keith Wansbrough's avatar Keith Wansbrough Committed by Jens Axboe
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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: default avatarKeith 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: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarJens Axboe <jens.axboe@oracle.com>
parent 061837bc

drivers/block/floppy.c

+15 −8
Original line number Diff line number Diff line
@@ -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();

include/linux/fd.h

+7 −1
Original line number Diff line number Diff line
@@ -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 */