| .. SPDX-License-Identifier: GPL-2.0+ | |
| Boot Count Limit | |
| ================ | |
| This allows to detect multiple failed attempts to boot Linux. | |
| After a power-on reset, "bootcount" variable will be initialized with 1, and | |
| each reboot will increment the value by 1. | |
| If, after a reboot, the new value of "bootcount" exceeds the value of | |
| "bootlimit", then instead of the standard boot action (executing the contents of | |
| "bootcmd") an alternate boot action will be performed, and the contents of | |
| "altbootcmd" will be executed. | |
| If the variable "bootlimit" is not defined in the environment, the Boot Count | |
| Limit feature is disabled. If it is enabled, but "altbootcmd" is not defined, | |
| then U-Boot will drop into interactive mode and remain there. | |
| It is the responsibility of some application code (typically a Linux | |
| application) to reset the variable "bootcount", thus allowing for more boot | |
| cycles. | |
| BOOTCOUNT_EXT | |
| ------------- | |
| This adds support for maintaining boot count in a file on an EXT filesystem. | |
| The file to use is define by: | |
| SYS_BOOTCOUNT_EXT_INTERFACE | |
| SYS_BOOTCOUNT_EXT_DEVPART | |
| SYS_BOOTCOUNT_EXT_NAME | |
| The format of the file is: | |
| ==== ================= | |
| type entry | |
| ==== ================= | |
| u8 magic | |
| u8 version | |
| u8 bootcount | |
| u8 upgrade_available | |
| ==== ================= | |
| To prevent unattended usage of "altbootcmd" the "upgrade_available" variable is | |
| used. | |
| If "upgrade_available" is 0, "bootcount" is not saved, if "upgrade_available" is | |
| 1 "bootcount" is save. | |
| So the Userspace Application must set the "upgrade_available" and "bootcount" | |
| variables to 0, if a boot was successfully. | |
| This also prevents writes on all reboots. |