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Author SHA1 Message Date
Simon Glass
179e219a3a doc: Tidy up the console docs a little
Tweak the documentation to look better when viewed. Use 'write' instead
of 'put'.

Series-to: concept
Series-version: 2
Cover-letter:
console: Refactor in preparation for the pager
This series tidies up a few small things the serial and console areas:

- Move detection of serial-console size to the serial module
- Provide a Kconfig to disable serial detection
- Fix some missing driver-model flags in stdio devices
- Move console docs into the main documentation

This series is marked v2 since some of the patches were sent in any
earlier series. With various tweaks that series grew too large to be
sent as a single series.
END

Signed-off-by: Simon Glass <sjg@chromium.org>
2025-08-25 07:26:58 -06:00

View File

@@ -6,10 +6,10 @@
U-Boot console handling U-Boot console handling
======================= =======================
HOW THE CONSOLE WORKS? Introduction
---------------------- ------------
At system startup U-Boot initializes a serial console. When U-Boot At system-startup U-Boot initializes a serial console. When U-Boot
relocates itself to RAM, all console drivers are initialized (they relocates itself to RAM, all console drivers are initialized (they
will register all detected console devices to the system for further will register all detected console devices to the system for further
use). use).
@@ -17,43 +17,46 @@ use).
If not defined in the environment, the first input device is assigned If not defined in the environment, the first input device is assigned
to the 'stdin' file, the first output one to 'stdout' and 'stderr'. to the 'stdin' file, the first output one to 'stdout' and 'stderr'.
You can use the command "coninfo" to see all registered console You can use the command `coninfo` to see all registered console
devices and their flags. You can assign a standard file (stdin, devices and their flags. You can assign a standard file (stdin,
stdout or stderr) to any device you see in that list simply by stdout or stderr) to any device you see in that list simply by
assigning its name to the corresponding environment variable. For assigning its name to the corresponding environment variable. For
example: example::
setenv stdin serial <- To use the serial input # Use the serial input
setenv stdout video <- To use the video console setenv stdin serial
Do a simple "saveenv" to save the console settings in the environment # Use the video console
setenv stdout vidconsole
Do a simple `saveenv` to save the console settings in the environment
and get them working on the next startup, too. and get them working on the next startup, too.
HOW CAN I USE STANDARD FILE INTO THE SOURCES? How to output text to the console
--------------------------------------------- ---------------------------------
You can use the following functions to access the console: You can use the following functions to access the console:
* STDOUT: stdout
putc (to put a char to stdout) - putc() - write a char to stdout
puts (to put a string to stdout) - puts() - write a string to stdout
printf (to format and put a string to stdout) - printf() - format and write a string to stdout
* STDIN: stdin
tstc (to test for the presence of a char in stdin) - tstc() - test for the presence of a char in stdin
getc (to get a char from stdin) - getchar() - get a char from stdin
* STDERR: stderr
eputc (to put a char to stderr) - eputc() - write a char to stderr
eputs (to put a string to stderr) - eputs() - write a string to stderr
eprintf (to format and put a string to stderr) - eprintf() - format and write a string to stderr
* FILE (can be 'stdin', 'stdout', 'stderr'): file ('stdin', 'stdout' or 'stderr')
fputc (like putc but redirected to a file) - fputc() - write a char to a file
fputs (like puts but redirected to a file) - fputs() - write a string to a file
fprintf (like printf but redirected to a file) - fprintf() - format and write a string to a file
ftstc (like tstc but redirected to a file) - ftstc() - test for the presence of a char in file
fgetc (like getc but redirected to a file) - fgetc() - get a char from a file
Remember that all FILE-related functions CANNOT be used before Remember that FILE-related functions CANNOT be used before U-Boot relocation,
U-Boot relocation (done in 'board_init_r' in `arch/*/lib/board.c`). which is done in `board_init_r()`.