Hi, I have with me a bunch of "raw" Micro SD Cards (which I got from a friend of my friend). Their capacity as reported by Linux/Windows is around 30 MB. Further, most of the fields in their CID and CSD register are empty. For example, the following values are set, Manufacturer ID: 0x00 ; OEM/Application ID: 0x2020 (or " "); Product name: 0x4e2f412020 (or "N/A "). The CSD structure version is set to 1 (which means SDSC card). I am told that these Micro SD cards are actually SDHC cards (anything between 4 GB - 32 GB). They are in pre-release state and a process called "upgrade" will make them realize their actual capacity, as noted in the previous statement instead of its current 30 MB. From what I have gathered from the documentation I need to modify C_SIZE, C_SIZE_MULT, READ_BL_LEN (from SD card specifications) to change the size of SD card. However, before trying to modify these values, I tried the following command dd if=/dev/zero of=/dev/mmcblk0 I expected that the whole disk will be written with zeros, and I can always use fdisk and mkfs to recreate the file system. However, I got a big surprise. When I open drive in fdisk and create partitions and save the partition table to the disk, nothing gets saved to the SD card. The device can't be formatted on windows either. Moreover, I created image of MBR, of another such raw SD card using the command, dd if=/dev/mmcblk0 of=mbr bs=512 count=1 and wrote it to the erring SD card using the command, dd if=mbr of=/dev/mmcblk0 bs=512 count=1 At this point I expected that at least partition table should be restored. But all this was to no avail. Moreover, a similar effort with a disk image of entire SD card (instead of just the initial 512 bytes) yielded no better results. From a look at the contents it would appear that no matter what I write to this SD card, its contents remain the same, and at the same time their is no error that is reported by the dd command. In the dmesg logs I can see the following output: [13534.411447] mmc0: new SD card at address 0002 [13534.411709] mmcblk0: mmc0:0002 N/A 30.0 MiB [13534.413899] mmcblk0: unknown partition table [13543.088097] mmcblk0: error -110 sending stop command, original cmd response 0x900, card status 0x580900 [13543.088152] mmcblk0: error -110 transferring data, sector 0, nr 8, cmd response 0x900, card status 0x0 [13543.088252] end_request: I/O error, dev mmcblk0, sector 1 [13543.088257] Buffer I/O error on device mmcblk0, logical block 0 [13543.088259] lost page write due to I/O error on mmcblk0 Can somebody help me understand two things: 1) Why is dd not able to write to the SD card? 2) Is there such a thing as "upgrade" process during manufacture of cards? If yes, how can I achieve the same in Linux? Please forgive me if this question does not belong to this mailing list. Thanks for a patient read. -N -- To unsubscribe from this list: send the line "unsubscribe linux-mmc" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
