[u-boot.git] / doc / README.console

/*
 * (C) Copyright 2000
 * Paolo Scaffardi, AIRVENT SAM s.p.a - RIMINI(ITALY), [email protected]
 *
 * SPDX-License-Identifier:	GPL-2.0+
 */

U-Boot console handling
========================

HOW THE CONSOLE WORKS?
----------------------

At system startup U-Boot initializes a serial console. When U-Boot
relocates itself to RAM, all console drivers are initialized (they
will register all detected console devices to the system for further
use).

If not defined in the environment, the first input device is assigned
to the 'stdin' file, the first output one to 'stdout' and 'stderr'.

You can use the command "coninfo" to see all registered console
devices and their flags. You can assign a standard file (stdin,
stdout or stderr) to any device you see in that list simply by
assigning its name to the corresponding environment variable. For
example:

    setenv stdin serial		<- To use the serial input
    setenv stdout video		<- To use the video console

Do a simple "saveenv" to save the console settings in the environment
and get them working on the next startup, too.

HOW CAN I USE STANDARD FILE INTO THE SOURCES?
---------------------------------------------

You can use the following functions to access the console:

* STDOUT:
    putc	(to put a char to stdout)
    puts	(to put a string to stdout)
    printf	(to format and put a string to stdout)

* STDIN:
    tstc	(to test for the presence of a char in stdin)
    getc	(to get a char from stdin)

* STDERR:
    eputc	(to put a char to stderr)
    eputs	(to put a string to stderr)
    eprintf	(to format and put a string to stderr)

* FILE (can be 'stdin', 'stdout', 'stderr'):
    fputc	(like putc but redirected to a file)
    fputs	(like puts but redirected to a file)
    fprintf	(like printf but redirected to a file)
    ftstc	(like tstc but redirected to a file)
    fgetc	(like getc but redirected to a file)

Remember that all FILE-related functions CANNOT be used before
U-Boot relocation (done in 'board_init_r' in arch/*/lib/board.c).

HOW CAN I USE STANDARD FILE INTO APPLICATIONS?
----------------------------------------------

Use the 'bd_mon_fnc' field of the bd_t structure passed to the
application to do everything you want with the console.

But REMEMBER that that will work only if you have not overwritten any
U-Boot code while loading (or uncompressing) the image of your
application.

For example, you won't get the console stuff running in the Linux
kernel because the kernel overwrites U-Boot before running. Only
some parameters like the framebuffer descriptors are passed to the
kernel in the high memory area to let the applications (the kernel)
use the framebuffers initialized by U-Boot.

SUPPORTED DRIVERS
-----------------

Working drivers:

    serial	(architecture dependent serial stuff)
    video	(mpc8xx video controller)

Work in progress:

    wl_kbd	(Wireless 4PPM keyboard)

Waiting for volounteers:

    lcd	(mpc8xx lcd controller; to )

TESTED CONFIGURATIONS
---------------------

The driver has been tested with the following configurations (see
CREDITS for other contact informations):

- MPC823FADS with AD7176 on a PAL TV (YCbYCr)	- [email protected]
Commit	Line	Data
cc1c8a13 WD	1	/*
	2	* (C) Copyright 2000
	3	* Paolo Scaffardi, AIRVENT SAM s.p.a - RIMINI(ITALY), [email protected]
	4	*
1a459660	5	* SPDX-License-Identifier: GPL-2.0+
cc1c8a13 WD	6	*/
	7
	8	U-Boot console handling
	9	========================
	10
	11	HOW THE CONSOLE WORKS?
	12	----------------------
	13
	14	At system startup U-Boot initializes a serial console. When U-Boot
	15	relocates itself to RAM, all console drivers are initialized (they
	16	will register all detected console devices to the system for further
	17	use).
	18
	19	If not defined in the environment, the first input device is assigned
	20	to the 'stdin' file, the first output one to 'stdout' and 'stderr'.
	21
	22	You can use the command "coninfo" to see all registered console
	23	devices and their flags. You can assign a standard file (stdin,
	24	stdout or stderr) to any device you see in that list simply by
	25	assigning its name to the corresponding environment variable. For
	26	example:
	27
dc2164da	28	setenv stdin serial <- To use the serial input
cc1c8a13 WD	29	setenv stdout video <- To use the video console
	30
	31	Do a simple "saveenv" to save the console settings in the environment
	32	and get them working on the next startup, too.
	33
	34	HOW CAN I USE STANDARD FILE INTO THE SOURCES?
	35	---------------------------------------------
	36
	37	You can use the following functions to access the console:
	38
	39	* STDOUT:
	40	putc (to put a char to stdout)
	41	puts (to put a string to stdout)
	42	printf (to format and put a string to stdout)
	43
	44	* STDIN:
	45	tstc (to test for the presence of a char in stdin)
	46	getc (to get a char from stdin)
	47
	48	* STDERR:
	49	eputc (to put a char to stderr)
	50	eputs (to put a string to stderr)
	51	eprintf (to format and put a string to stderr)
	52
	53	* FILE (can be 'stdin', 'stdout', 'stderr'):
	54	fputc (like putc but redirected to a file)
	55	fputs (like puts but redirected to a file)
	56	fprintf (like printf but redirected to a file)
	57	ftstc (like tstc but redirected to a file)
	58	fgetc (like getc but redirected to a file)
	59
	60	Remember that all FILE-related functions CANNOT be used before
7de17781	61	U-Boot relocation (done in 'board_init_r' in arch/*/lib/board.c).
cc1c8a13 WD	62
	63	HOW CAN I USE STANDARD FILE INTO APPLICATIONS?
	64	----------------------------------------------
	65
	66	Use the 'bd_mon_fnc' field of the bd_t structure passed to the
	67	application to do everything you want with the console.
	68
	69	But REMEMBER that that will work only if you have not overwritten any
	70	U-Boot code while loading (or uncompressing) the image of your
	71	application.
	72
	73	For example, you won't get the console stuff running in the Linux
	74	kernel because the kernel overwrites U-Boot before running. Only
	75	some parameters like the framebuffer descriptors are passed to the
	76	kernel in the high memory area to let the applications (the kernel)
	77	use the framebuffers initialized by U-Boot.
	78
	79	SUPPORTED DRIVERS
	80	-----------------
	81
	82	Working drivers:
	83
53677ef1 WD	84	serial (architecture dependent serial stuff)
53677ef1 WD	85	video (mpc8xx video controller)
cc1c8a13 WD	86
	87	Work in progress:
	88
	89	wl_kbd (Wireless 4PPM keyboard)
	90
	91	Waiting for volounteers:
	92
	93	lcd (mpc8xx lcd controller; to )
	94
	95	TESTED CONFIGURATIONS
	96	---------------------
	97
	98	The driver has been tested with the following configurations (see
	99	CREDITS for other contact informations):
	100
53677ef1	101	- MPC823FADS with AD7176 on a PAL TV (YCbYCr) - [email protected]