101 lines
3.1 KiB
Plaintext
101 lines
3.1 KiB
Plaintext
SPDX-License-Identifier: GPL-2.0+
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/*
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* (C) Copyright 2000
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* Paolo Scaffardi, AIRVENT SAM s.p.a - RIMINI(ITALY), arsenio@tin.it
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*/
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U-Boot console handling
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========================
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HOW THE CONSOLE WORKS?
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----------------------
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At system startup U-Boot initializes a serial console. When U-Boot
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relocates itself to RAM, all console drivers are initialized (they
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will register all detected console devices to the system for further
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use).
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If not defined in the environment, the first input device is assigned
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to the 'stdin' file, the first output one to 'stdout' and 'stderr'.
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You can use the command "coninfo" to see all registered console
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devices and their flags. You can assign a standard file (stdin,
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stdout or stderr) to any device you see in that list simply by
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assigning its name to the corresponding environment variable. For
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example:
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setenv stdin serial <- To use the serial input
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setenv stdout video <- To use the video console
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Do a simple "saveenv" to save the console settings in the environment
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and get them working on the next startup, too.
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HOW CAN I USE STANDARD FILE INTO THE SOURCES?
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---------------------------------------------
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You can use the following functions to access the console:
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* STDOUT:
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putc (to put a char to stdout)
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puts (to put a string to stdout)
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printf (to format and put a string to stdout)
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* STDIN:
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tstc (to test for the presence of a char in stdin)
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getc (to get a char from stdin)
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* STDERR:
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eputc (to put a char to stderr)
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eputs (to put a string to stderr)
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eprintf (to format and put a string to stderr)
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* FILE (can be 'stdin', 'stdout', 'stderr'):
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fputc (like putc but redirected to a file)
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fputs (like puts but redirected to a file)
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fprintf (like printf but redirected to a file)
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ftstc (like tstc but redirected to a file)
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fgetc (like getc but redirected to a file)
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Remember that all FILE-related functions CANNOT be used before
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U-Boot relocation (done in 'board_init_r' in arch/*/lib/board.c).
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HOW CAN I USE STANDARD FILE INTO APPLICATIONS?
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----------------------------------------------
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Use the 'bd_mon_fnc' field of the bd_t structure passed to the
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application to do everything you want with the console.
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But REMEMBER that that will work only if you have not overwritten any
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U-Boot code while loading (or uncompressing) the image of your
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application.
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For example, you won't get the console stuff running in the Linux
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kernel because the kernel overwrites U-Boot before running. Only
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some parameters like the framebuffer descriptors are passed to the
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kernel in the high memory area to let the applications (the kernel)
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use the framebuffers initialized by U-Boot.
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SUPPORTED DRIVERS
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-----------------
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Working drivers:
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serial (architecture dependent serial stuff)
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video (mpc8xx video controller)
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Work in progress:
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wl_kbd (Wireless 4PPM keyboard)
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Waiting for volounteers:
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lcd (mpc8xx lcd controller; to )
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TESTED CONFIGURATIONS
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---------------------
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The driver has been tested with the following configurations (see
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CREDITS for other contact informations):
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- MPC823FADS with AD7176 on a PAL TV (YCbYCr) - arsenio@tin.it
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