1 ============================
2 SD and MMC Device Partitions
3 ============================
4
5 Device partitions are additional logical block
6 SD/MMC device.
7
8 As of this writing, MMC boot partitions as sup
9 /dev/mmcblkXboot0 and /dev/mmcblkXboot1, where
10 parent /dev/mmcblkX.
11
12 MMC Boot Partitions
13 ===================
14
15 Read and write access is provided to the two M
16 the sensitive nature of the boot partition con
17 a bootloader or bootloader configuration table
18 platform, write access is disabled by default
19 accidental bricking.
20
21 To enable write access to /dev/mmcblkXbootY, d
22 access with::
23
24 echo 0 > /sys/block/mmcblkXbootY/force
25
26 To re-enable read-only access::
27
28 echo 1 > /sys/block/mmcblkXbootY/force
29
30 The boot partitions can also be locked read on
31 with::
32
33 echo 1 > /sys/block/mmcblkXbootY/ro_lo
34
35 This is a feature of the card and not of the k
36 not support boot partition locking, the file w
37 feature has been disabled on the card, the fil
38
39 The boot partitions can also be locked permane
40 not accessible through sysfs in order to avoid
41 bricking.
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