On Fri, Aug 12, 2005 at 09:16:56PM +0530, Mukund JB. wrote: > When I said mount, I guess FAT will read sector 0 to get the partition > info. And is it due to lack of partition support in the driver that will > affect the FAT layer reading the device. > Please update?
No, the kernel read the partition table if it is there, and presents each partition as a device. The user can then mount the partition or the whole device (whichever is appropriate for the card) using the FAT filesystem driver. The fat driver only works when pointed at the right location and has no clue about partitions (and it should not have a clue). > Yes, right, my card size if 16 MB. FS type is FAT12. > > The SD card has partitions on it (both: cam, windows). > So, my device node accessing is direct. > You can see below the SD card has a single primary partition. > > So, I say "mount -tvfat /dev/tfa0 /mnt" which works for windows > formatted SD. > The same does NOT work with CAM formatted SD. Well if you ignore the partition table and just use a hardcoded offset to the start of the partition, well then it likely won't work if the partitioning layout is different for the two cards. > Sfdisk -l /dev/tfa0 ( CAM & win) > Disk /dev/tfa0: 448 cylinders, 2 heads, 32 sectors/track > Units = cylinders of 32768 bytes, blocks of 1024 bytes, counting from 0 > > Device Boot Start End #cyls #blocks Id System > /dev/tfa0p1 * 0+ 449 450- 14371+ 1 FAT12 > /dev/tfa0p2 0 - 0 0 0 Empty > /dev/tfa0p3 0 - 0 0 0 Empty > /dev/tfa0p4 0 - 0 0 0 Empty > Warning: partition 1 extends past end of disk > > I don't understand, what is /dev/tfa0p1? I have no such device. Well that would be the partition 1 on the tfa0 device, which you need since that card has a partition there. > Will you please elaborate this? > What kind of partition support is required in the driver to support the > Camera Fat12 formatted SD Card? > > I dumped the 1st sector of SD when formatted on CAM. > I have attached the files. Please have a look at them > > Cluster-0.txt - First 16 Blocks of the device > Phy-Cam-57-sector.txt - 57th sector of the device (claimed FAT > sector > in Partition table) Well one of the two files you sent appears to contain a FAT12 filesystem directly on the device and has no partitions. The other appears to contain a partition table with one partition, and I suspect that partition contains a FAT12 filesystem. To read one you access the whole device and mount that. To access the other you have to use the partition and mount that instead. This is why your driver MUST support partitions, or at the very least look for a partition table, and if it sees one, skip to the sector the partition table says is the start and present the device from that location on as the device (although that MAY mess up FAT, since I don't know if fat uses relative sector numbers from the start of the partition, or physical drive sector numbers. I would think it was relative, in which case you should be ok just offseting all requests to the device by the number of sectors to the start of the partition found. So for the device above with one partition, you would have to check the partition table entry to find the start sector number of the partition and then offset requests by that amount. For example: fdisk -l -u /dev/sde: debdev1:~# fdisk -l -u /dev/sde Disk /dev/sde: 14 MB, 14745600 bytes 2 heads, 32 sectors/track, 450 cylinders, total 28800 sectors Units = sectors of 1 * 512 = 512 bytes Device Boot Start End Blocks Id System /dev/sde1 57 28799 14371+ 1 FAT12 So if you skip 57 sectors you would see the FAT12 filesystem. On your card without a partition table, the FAT12 starts at sector 0, on the other it is offset by the number of sectors to the start of the first partition. Len Sorensen - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
