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Diffstat (limited to 'qemu/roms/u-boot/doc/README.autoboot')
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diff --git a/qemu/roms/u-boot/doc/README.autoboot b/qemu/roms/u-boot/doc/README.autoboot deleted file mode 100644 index 14e3660dd..000000000 --- a/qemu/roms/u-boot/doc/README.autoboot +++ /dev/null @@ -1,157 +0,0 @@ -/* - * (C) Copyright 2001 - * Dave Ellis, SIXNET, dge@sixnetio.com - * - * SPDX-License-Identifier: GPL-2.0+ - */ - -Using autoboot configuration options -==================================== - -The basic autoboot configuration options are documented in the main -U-Boot README. See it for details. They are: - - bootdelay - bootcmd - CONFIG_BOOTDELAY - CONFIG_BOOTCOMMAND - -Some additional options that make autoboot safer in a production -product are documented here. - -Why use them? -------------- - -The basic autoboot feature allows a system to automatically boot to -the real application (such as Linux) without a user having to enter -any commands. If any key is pressed before the boot delay time -expires, U-Boot stops the autoboot process, gives a U-Boot prompt -and waits forever for a command. That's a good thing if you pressed a -key because you wanted to get the prompt. - -It's not so good if the key press was a stray character on the -console serial port, say because a user who knows nothing about -U-Boot pressed a key before the system had time to boot. It's even -worse on an embedded product that doesn't have a console during -normal use. The modem plugged into that console port sends a -character at the wrong time and the system hangs, with no clue as to -why it isn't working. - -You might want the system to autoboot to recover after an external -configuration program stops autoboot. If the configuration program -dies or loses its connection (modems can disconnect at the worst -time) U-Boot will patiently wait forever for it to finish. - -These additional configuration options can help provide a system that -boots when it should, but still allows access to U-Boot. - -What they do ------------- - - CONFIG_BOOT_RETRY_TIME - CONFIG_BOOT_RETRY_MIN - - "bootretry" environment variable - - These options determine what happens after autoboot is - stopped and U-Boot is waiting for commands. - - CONFIG_BOOT_RETRY_TIME must be defined to enable the boot - retry feature. If the environment variable "bootretry" is - found then its value is used, otherwise the retry timeout is - CONFIG_BOOT_RETRY_TIME. CONFIG_BOOT_RETRY_MIN is optional and - defaults to CONFIG_BOOT_RETRY_TIME. All times are in seconds. - - If the retry timeout is negative, the U-Boot command prompt - never times out. Otherwise it is forced to be at least - CONFIG_BOOT_RETRY_MIN seconds. If no valid U-Boot command is - entered before the specified time the boot delay sequence is - restarted. Each command that U-Boot executes restarts the - timeout. - - If CONFIG_BOOT_RETRY_TIME < 0 the feature is there, but - doesn't do anything unless the environment variable - "bootretry" is >= 0. - - CONFIG_AUTOBOOT_KEYED - CONFIG_AUTOBOOT_KEYED_CTRLC - CONFIG_AUTOBOOT_PROMPT - CONFIG_AUTOBOOT_DELAY_STR - CONFIG_AUTOBOOT_STOP_STR - CONFIG_AUTOBOOT_DELAY_STR2 - CONFIG_AUTOBOOT_STOP_STR2 - - "bootdelaykey" environment variable - "bootstopkey" environment variable - "bootdelaykey2" environment variable - "bootstopkey2" environment variable - - These options give more control over stopping autoboot. When - they are used a specific character or string is required to - stop or delay autoboot. - - Define CONFIG_AUTOBOOT_KEYED (no value required) to enable - this group of options. CONFIG_AUTOBOOT_DELAY_STR, - CONFIG_AUTOBOOT_STOP_STR or both should be specified (or - specified by the corresponding environment variable), - otherwise there is no way to stop autoboot. - - CONFIG_AUTOBOOT_PROMPT is displayed before the boot delay - selected by CONFIG_BOOTDELAY starts. If it is not defined - there is no output indicating that autoboot is in progress. - - Note that CONFIG_AUTOBOOT_PROMPT is used as the (only) - argument to a printf() call, so it may contain '%' format - specifications, provided that it also includes, sepearated by - commas exactly like in a printf statement, the required - arguments. It is the responsibility of the user to select only - such arguments that are valid in the given context. A - reasonable prompt could be defined as - - #define CONFIG_AUTOBOOT_PROMPT \ - "autoboot in %d seconds\n",bootdelay - - If CONFIG_AUTOBOOT_DELAY_STR or "bootdelaykey" is specified - and this string is received from console input before - autoboot starts booting, U-Boot gives a command prompt. The - U-Boot prompt will time out if CONFIG_BOOT_RETRY_TIME is - used, otherwise it never times out. - - If CONFIG_AUTOBOOT_STOP_STR or "bootstopkey" is specified and - this string is received from console input before autoboot - starts booting, U-Boot gives a command prompt. The U-Boot - prompt never times out, even if CONFIG_BOOT_RETRY_TIME is - used. - - The string recognition is not very sophisticated. If a - partial match is detected, the first non-matching character - is checked to see if starts a new match. There is no check - for a shorter partial match, so it's best if the first - character of a key string does not appear in the rest of the - string. - - Using the CONFIG_AUTOBOOT_DELAY_STR2 #define or the - "bootdelaykey2" environment variable and/or the - CONFIG_AUTOBOOT_STOP_STR2 #define or the "bootstopkey" - environment variable you can specify a second, alternate - string (which allows you to have two "password" strings). - - The CONFIG_AUTOBOOT_KEYED_CTRLC #define allows for the boot - sequence to be interrupted by ctrl-c, in addition to the - "bootdelaykey" and "bootstopkey". Setting this variable - provides an escape sequence from the limited "password" - strings. - - - CONFIG_ZERO_BOOTDELAY_CHECK - - If this option is defined, you can stop the autoboot process - by hitting a key even in that case when "bootdelay" has been - set to 0. You can set "bootdelay" to a negative value to - prevent the check for console input. - - CONFIG_RESET_TO_RETRY - - (Only effective when CONFIG_BOOT_RETRY_TIME is also set) - After the countdown timed out, the board will be reset to restart - again. |