From 9d54c8a33eec78289b1b3f6e10874719c27ce0a7 Mon Sep 17 00:00:00 2001 From: Ezequiel Garcia Date: Tue, 25 Feb 2014 13:25:22 -0300 Subject: UBI: R/O block driver on top of UBI volumes This commit introduces read-only block device emulation on top of UBI volumes. Given UBI takes care of wear leveling and bad block management it's possible to add a thin layer to enable block device access to UBI volumes. This allows to use a block-oriented filesystem on a flash device. The UBI block devices are meant to be used in conjunction with any regular, block-oriented file system (e.g. ext4), although it's primarily targeted at read-only file systems, such as squashfs. Block devices are created upon user request through new ioctls: UBI_IOCVOLATTBLK to attach and UBI_IOCVOLDETBLK to detach. Also, a new UBI module parameter is added 'ubi.block'. This parameter is needed in order to attach a block device on boot-up time, allowing to mount the rootfs on a ubiblock device. For instance, you could have these kernel parameters: ubi.mtd=5 ubi.block=0,0 root=/dev/ubiblock0_0 Or, if you compile ubi as a module: $ modprobe ubi mtd=/dev/mtd5 block=/dev/ubi0_0 Artem: amend commentaries and massage the patch a little bit. Signed-off-by: Ezequiel Garcia Signed-off-by: Artem Bityutskiy --- drivers/mtd/ubi/Kconfig | 15 +++++++++++++++ 1 file changed, 15 insertions(+) (limited to 'drivers/mtd/ubi/Kconfig') diff --git a/drivers/mtd/ubi/Kconfig b/drivers/mtd/ubi/Kconfig index 36663af56d89..783fb186d876 100644 --- a/drivers/mtd/ubi/Kconfig +++ b/drivers/mtd/ubi/Kconfig @@ -87,4 +87,19 @@ config MTD_UBI_GLUEBI work on top of UBI. Do not enable this unless you use legacy software. +config MTD_UBI_BLOCK + bool "Read-only block devices on top of UBI volumes" + default n + help + This option enables read-only UBI block devices support. UBI block + devices will be layered on top of UBI volumes, which means that the + UBI driver will transparently handle things like bad eraseblocks and + bit-flips. You can put any block-oriented file system on top of UBI + volumes in read-only mode (e.g., ext4), but it is probably most + practical for read-only file systems, like squashfs. + + When selected, this feature will be built in the UBI driver. + + If in doubt, say "N". + endif # MTD_UBI -- cgit