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Date: Sat, 9 Aug 2008 19:42:14 +0100
From: Keith Wansbrough <keith@...han.org>
To: Jens Axboe <axboe@...nel.dk>, Alain Knaff <alain@...ux.lu>
Cc: linux-kernel@...r.kernel.org, Gene Heskett <gene.heskett@...il.com>
Subject: [PATCH] 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@...han.org>
---
I've tested formatting, writing, and reading disks with a variety of
first sector numbers (including 0 and 1), and all works as expected.
I have made corresponding changes to fdutils, which I will submit
separately to the fdutils maintainer.
There's no floppy maintainer listed in MAINTAINERS, so this is sent to
the block subsystem maintainer and to the fdutils maintainer. I'm cc:ing
Gene because I know he's been working in this area recently.
--KW 8-)
Index: linux-2.6.27-rc1-git4/drivers/block/floppy.c
===================================================================
--- linux-2.6.27-rc1-git4.orig/drivers/block/floppy.c 2008-08-02 23:36:32.000000000 +0100
+++ linux-2.6.27-rc1-git4/drivers/block/floppy.c 2008-08-02 23:36:37.000000000 +0100
@@ -423,8 +423,15 @@ static struct floppy_raw_cmd *raw_cmd, d
* 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 trac
}
}
}
- 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
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
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();
Index: linux-2.6.27-rc1-git4/include/linux/fd.h
===================================================================
--- linux-2.6.27-rc1-git4.orig/include/linux/fd.h 2008-08-02 23:36:32.000000000 +0100
+++ linux-2.6.27-rc1-git4/include/linux/fd.h 2008-08-02 23:36:37.000000000 +0100
@@ -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 */
--
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