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fatfs: add FAT_IOCTL_GET_VOLUME_ID

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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 <[email protected]>
Cc: dmitry pervushin <[email protected]>
Cc: Mike Lockwood <[email protected]>
Cc: Colin Cross <[email protected]>
Acked-by: OGAWA Hirofumi <[email protected]>
Cc: John Stultz <[email protected]>
Cc: Sean McNeil <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>
This commit is contained in:
Mike Lockwood 2013-07-08 16:00:46 -07:00 • committed by Linus Torvalds
commit 6e5b93ee55
4 changed files with 31 additions and 0 deletions
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1
fs/fat/fat.h
View file

@ -86,6 +86,7 @@ struct msdos_sb_info {
const void *dir_ops; /* Opaque; default directory operations */
int dir_per_block; /* dir entries per block */
int dir_per_block_bits; /* log2(dir_per_block) */
unsigned int vol_id; /*volume ID*/
int fatent_shift;
struct fatent_operations *fatent_ops;

8
fs/fat/file.c
View file

@ -114,6 +114,12 @@ out:
return err;
}
static int fat_ioctl_get_volume_id(struct inode *inode, u32 __user *user_attr)
{
struct msdos_sb_info *sbi = MSDOS_SB(inode->i_sb);
return put_user(sbi->vol_id, user_attr);
}
long fat_generic_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
{
struct inode *inode = file_inode(filp);
@ -124,6 +130,8 @@ long fat_generic_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
return fat_ioctl_get_attributes(inode, user_attr);
case FAT_IOCTL_SET_ATTRIBUTES:
return fat_ioctl_set_attributes(filp, user_attr);
case FAT_IOCTL_GET_VOLUME_ID:
return fat_ioctl_get_volume_id(inode, user_attr);
default:
return -ENOTTY; /* Inappropriate ioctl for device */
}

12
fs/fat/inode.c
View file

@ -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;