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 --- include/uapi/mtd/ubi-user.h | 11 +++++++++++ 1 file changed, 11 insertions(+) (limited to 'include/uapi/mtd') diff --git a/include/uapi/mtd/ubi-user.h b/include/uapi/mtd/ubi-user.h index 723c324590c1..b98585ad3346 100644 --- a/include/uapi/mtd/ubi-user.h +++ b/include/uapi/mtd/ubi-user.h @@ -134,6 +134,13 @@ * used. A pointer to a &struct ubi_set_vol_prop_req object is expected to be * passed. The object describes which property should be set, and to which value * it should be set. + * + * Block devices on UBI volumes + * ~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + * + * To attach or detach a block device from an UBI volume the %UBI_IOCVOLATTBLK + * and %UBI_IOCVOLDETBLK ioctl commands should be used, respectively. + * These commands take no arguments. */ /* @@ -191,6 +198,10 @@ /* Set an UBI volume property */ #define UBI_IOCSETVOLPROP _IOW(UBI_VOL_IOC_MAGIC, 6, \ struct ubi_set_vol_prop_req) +/* Attach a block device to an UBI volume */ +#define UBI_IOCVOLATTBLK _IO(UBI_VOL_IOC_MAGIC, 7) +/* Detach a block device from an UBI volume */ +#define UBI_IOCVOLDETBLK _IO(UBI_VOL_IOC_MAGIC, 8) /* Maximum MTD device name length supported by UBI */ #define MAX_UBI_MTD_NAME_LEN 127 -- cgit v1.2.3