CONFIG_MTD Memory Technology Devices are flash, RAM and similar chips, often used for solid state file systems on embedded devices. This option will provide the generic support for MTD drivers to register themselves with the kernel and for potential users of MTD devices to enumerate the devices which are present and obtain a handle on them. It will also allow you to select individual drivers for particular hardware and users of MTD devices. If unsure, say N. CONFIG_MTD_DEBUG This turns on low-level debugging for the entire MTD sub-system. Normally, you should say 'N'. CONFIG_MTD_PARTITIONS If you have a device which needs to divide its flash chip(s) up into multiple 'partitions', each of which appears to the user as a separate MTD device, you require this option to be enabled. If unsure, say 'Y'. Note, however, that you don't need this option for the DiskOnChip devices. Partitioning on NFTL 'devices' is a different - that's the 'normal' form of partitioning used on a block device. CONFIG_MTD_REDBOOT_PARTS RedBoot is a ROM monitor and bootloader which deals with multiple 'images' in flash devices by putting a table in the last erase block of the device, similar to a partition table, which gives the offsets, lengths and names of all the images stored in the flash. If you need code which can detect and parse this table, and register MTD 'partitions' corresponding to each image in the table, enable this option. You will still need the parsing functions to be called by the driver for your particular device. It won't happen automatically. The SA1100 map driver (CONFIG_MTD_SA1100) has an option for this, for example. CONFIG_MTD_BOOTLDR_PARTS The Compaq bootldr deals with multiple 'images' in flash devices by putting a table in one of the first erase blocks of the device, similar to a partition table, which gives the offsets, lengths and names of all the images stored in the flash. If you need code which can detect and parse this table, and register MTD 'partitions' corresponding to each image in the table, enable this option. You will still need the parsing functions to be called by the driver for your particular device. It won't happen automatically. The SA1100 map driver (CONFIG_MTD_SA1100) has an option for this, for example. CONFIG_MTD_AFS_PARTS The ARM Firmware Suite allows the user to divide flash devices into multiple 'images'. Each such image has a header containing its name and offset/size etc. If you need code which can detect and parse these tables, and register MTD 'partitions' corresponding to each image detected, enable this option. You will still need the parsing functions to be called by the driver for your particular device. It won't happen automatically. The 'armflash' map driver (CONFIG_MTD_ARMFLASH) does this, for example. CONFIG_MTD_DEBUG_VERBOSE Determines the verbosity level of the MTD debugging messages. CONFIG_MTD_CHAR This provides a character device for each MTD device present in the system, allowing the user to read and write directly to the memory chips, and also use ioctl() to obtain information about the device, or to erase parts of it. CONFIG_MTD_BLOCK Although most flash chips have an erase size too large to be useful as block devices, it is possible to use MTD devices which are based on RAM chips in this manner. This block device is a user of MTD devices performing that function. At the moment, it is also required for the Journalling Flash File System(s) to obtain a handle on the MTD device when it's mounted (although JFFS and JFFS2 don't actually use any of the functionality of the mtdblock device). Later, it may be extended to perform read/erase/modify/write cycles on flash chips to emulate a smaller block size. Needless to say, this is very unsafe, but could be useful for file systems which are almost never written to. You do not need this option for use with the DiskOnChip devices. For those, enable NFTL support (CONFIG_NFTL) instead. CONFIG_MTD_BLOCK_RO This allows you to mount read-only file systems (such as cramfs) from an MTD device, without the overhead (and danger) of the caching driver. You do not need this option for use with the DiskOnChip devices. For those, enable NFTL support (CONFIG_NFTL) instead. CONFIG_FTL This provides support for the original Flash Translation Layer which is part of the PCMCIA specification. It uses a kind of pseudo- file system on a flash device to emulate a block device with 512-byte sectors, on top of which you put a 'normal' file system. You may find that the algorithms used in this code are patented unless you live in the Free World where software patents aren't legal - in the USA you are only permitted to use this on PCMCIA hardware, although under the terms of the GPL you're obviously permitted to copy, modify and distribute the code as you wish. Just not use it. CONFIG_NFTL This provides support for the NAND Flash Translation Layer which is used on M-Systems' DiskOnChip devices. It uses a kind of pseudo- file system on a flash device to emulate a block device with 512-byte sectors, on top of which you put a 'normal' file system. You may find that the algorithms used in this code are patented unless you live in the Free World where software patents aren't legal - in the USA you are only permitted to use this on DiskOnChip hardware, although under the terms of the GPL you're obviously permitted to copy, modify and distribute the code as you wish. Just not use it. CONFIG_NFTL_RW If you're lucky, this will actually work. Don't whinge if it doesn't. Send mail to the MTD mailing list if you want to help to make it more reliable.