From 9e49184c82e9ec3ab4d45f9ea5a17ccaf43869f0 Mon Sep 17 00:00:00 2001 From: Keith Wansbrough Date: Mon, 22 Sep 2008 14:57:17 -0700 Subject: 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 Cc: Alain Knaff Cc: Michael Kerrisk Cc: Karel Zak Signed-off-by: Andrew Morton Signed-off-by: Jens Axboe --- include/linux/fd.h | 8 +++++++- 1 file changed, 7 insertions(+), 1 deletion(-) (limited to 'include/linux/fd.h') diff --git a/include/linux/fd.h b/include/linux/fd.h index b6bd41d2b460..f5d194af07a8 100644 --- a/include/linux/fd.h +++ b/include/linux/fd.h @@ -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 */ -- cgit v1.2.3