From 6e5b93ee55d401f1619092fb675b57c28c9ed7ec Mon Sep 17 00:00:00 2001 From: Mike Lockwood Date: Mon, 8 Jul 2013 16:00:46 -0700 Subject: fatfs: add FAT_IOCTL_GET_VOLUME_ID This patch, originally from Android kernel, adds vfat ioctl command FAT_IOCTL_GET_VOLUME_ID, with this command we can get the vfat volume ID using following code: ioctl(fd, FAT_IOCTL_GET_VOLUME_ID, &volume_ID) This patch is a modified version of the patch by Mike Lockwood, with changes from Dmitry Pervushin, who noticed the original patch makes some volume IDs abiguous with error returns: for example, if volume id is 0xFFFFFDAD, that matches -ENOIOCTLCMD, we get "FFFFFFFF" from the user space. So add a parameter to ioctl to get the correct volume ID. Android uses vfat volume ID to identify different sd card, when a new sd card is inserted to device, android can scan the media on it and pop up new contents. Signed-off-by: Bintian Wang Cc: dmitry pervushin Cc: Mike Lockwood Cc: Colin Cross Acked-by: OGAWA Hirofumi Cc: John Stultz Cc: Sean McNeil Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- fs/fat/inode.c | 12 ++++++++++++ 1 file changed, 12 insertions(+) (limited to 'fs/fat/inode.c') diff --git a/fs/fat/inode.c b/fs/fat/inode.c index 5d4513cb1b3c..11b51bb55b42 100644 --- a/fs/fat/inode.c +++ b/fs/fat/inode.c @@ -1415,6 +1415,18 @@ int fat_fill_super(struct super_block *sb, void *data, int silent, int isvfat, brelse(fsinfo_bh); } + /* interpret volume ID as a little endian 32 bit integer */ + if (sbi->fat_bits == 32) + sbi->vol_id = (((u32)b->fat32.vol_id[0]) | + ((u32)b->fat32.vol_id[1] << 8) | + ((u32)b->fat32.vol_id[2] << 16) | + ((u32)b->fat32.vol_id[3] << 24)); + else /* fat 16 or 12 */ + sbi->vol_id = (((u32)b->fat16.vol_id[0]) | + ((u32)b->fat16.vol_id[1] << 8) | + ((u32)b->fat16.vol_id[2] << 16) | + ((u32)b->fat16.vol_id[3] << 24)); + sbi->dir_per_block = sb->s_blocksize / sizeof(struct msdos_dir_entry); sbi->dir_per_block_bits = ffs(sbi->dir_per_block) - 1; -- cgit v1.2.3