mirror of
https://github.com/AsahiLinux/u-boot
synced 2024-11-18 02:38:56 +00:00
16a28ef219
Modifications to support console multiplexing. This is controlled using CONFIG_SYS_CONSOLE_MUX in the board configuration file. This allows a user to specify multiple console devices in the environment with a command like this: setenv stdin serial,nc. As a result, the user can enter text on both the serial and netconsole interfaces. All devices - stdin, stdout and stderr - can be set in this manner. 1) common/iomux.c and include/iomux.h contain the environment setting implementation. 2) doc/README.iomux contains a somewhat more detailed description. 3) The implementation in (1) is called from common/cmd_nvedit.c to handle setenv and from common/console.c to handle initialization of input/output devices at boot time. 4) common/console.c also contains the code needed to poll multiple console devices for input and send output to all devices registered for output. 5) include/common.h includes iomux.h and common/Makefile generates iomux.o when CONFIG_SYS_CONSOLE_MUX is set. Signed-off-by: Gary Jennejohn <garyj@denx.de>
106 lines
4.4 KiB
Text
106 lines
4.4 KiB
Text
/*
|
|
* (C) Copyright 2008
|
|
* Gary Jennejohn, DENX Software Engineering GmbH <garyj@denx.de>
|
|
*
|
|
* See file CREDITS for list of people who contributed to this
|
|
* project.
|
|
*
|
|
* This program is free software; you can redistribute it and/or
|
|
* modify it under the terms of the GNU General Public License as
|
|
* published by the Free Software Foundation; either version 2 of
|
|
* the License, or (at your option) any later version.
|
|
*
|
|
* This program is distributed in the hope that it will be useful,
|
|
* but WITHOUT ANY WARRANTY; without even the implied warranty of
|
|
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
|
|
* GNU General Public License for more details.
|
|
*
|
|
* You should have received a copy of the GNU General Public License
|
|
* along with this program; if not, write to the Free Software
|
|
* Foundation, Inc., 59 Temple Place, Suite 330, Boston,
|
|
* MA 02111-1307 USA
|
|
*/
|
|
|
|
U-Boot console multiplexing
|
|
===========================
|
|
|
|
HOW CONSOLE MULTIPLEXING WORKS
|
|
------------------------------
|
|
|
|
This functionality is controlled with CONFIG_CONSOLE_MUX in the board
|
|
configuration file.
|
|
|
|
Two new files, common/iomux.c and include/iomux.h, contain the heart
|
|
(iomux_doenv()) of the environment setting implementation.
|
|
|
|
iomux_doenv() is called in common/cmd_nvedit.c to handle setenv and in
|
|
common/console.c in console_init_r() during bootup to initialize
|
|
stdio_devices[].
|
|
|
|
A user can use a comma-separated list of devices to set stdin, stdout
|
|
and stderr. For example: "setenv stdin serial,nc". NOTE: No spaces
|
|
are allowed around the comma(s)!
|
|
|
|
The length of the list is limited by malloc(), since the array used
|
|
is allocated and freed dynamically.
|
|
|
|
It should be possible to specify any device which console_assign()
|
|
finds acceptable, but the code has only been tested with serial and
|
|
nc.
|
|
|
|
iomux_doenv() prevents multiple use of the same device, e.g. "setenv
|
|
stdin nc,nc,serial" will discard the second nc. iomux_doenv() is
|
|
not able to modify the environment, however, so that "pri stdin" still
|
|
shows "nc,nc,serial".
|
|
|
|
The major change in common/console.c was to modify fgetc() to call
|
|
the iomux_tstc() routine in a for-loop. iomux_tstc() in turn calls
|
|
the tstc() routine for every registered device, but exits immediately
|
|
when one of them returns true. fgetc() then calls iomux_getc(),
|
|
which calls the corresponding getc() routine. fgetc() hangs in
|
|
the for-loop until iomux_tstc() returns true and the input can be
|
|
retrieved.
|
|
|
|
Thus, a user can type into any device registered for stdin. No effort
|
|
has been made to demulitplex simultaneous input from multiple stdin
|
|
devices.
|
|
|
|
fputc() and fputs() have been modified to call iomux_putc() and
|
|
iomux_puts() respectively, which call the corresponding output
|
|
routines for every registered device.
|
|
|
|
Thus, a user can see the ouput for any device registered for stdout
|
|
or stderr on all devices registered for stdout or stderr. As an
|
|
example, if stdin=serial,nc and stdout=serial,nc then all output
|
|
for serial, e.g. echos of input on serial, will appear on serial and nc.
|
|
|
|
Just as with the old console code, this statement is still true:
|
|
If not defined in the environment, the first input device is assigned
|
|
to the 'stdin' file, the first output one to 'stdout' and 'stderr'.
|
|
|
|
If CONFIG_SYS_CONSOLE_IS_IN_ENV is defined then multiple input/output
|
|
devices can be set at boot time if defined in the environment.
|
|
|
|
CAVEATS
|
|
-------
|
|
|
|
Note that common/iomux.c calls console_assign() for every registered
|
|
device as it is discovered. This means that the environment settings
|
|
for application consoles will be set to the last device in the list.
|
|
|
|
On a slow machine, such as MPC852T clocked at 66MHz, the overhead associated
|
|
with calling tstc() and then getc() means that copy&paste will normally not
|
|
work, even when stdin=stdout=stderr=serial.
|
|
On a faster machine, such as a sequoia, cut&paste of longer (about 80
|
|
characters) lines works fine when serial is the only device used.
|
|
|
|
Using nc as a stdin device results in even more overhead because nc_tstc()
|
|
is quite slow. Even on a sequoia cut&paste does not work on the serial
|
|
interface when nc is added to stdin, although there is no character loss using
|
|
the ethernet interface for input. In this test case stdin=serial,nc and
|
|
stdout=serial.
|
|
|
|
In addition, the overhead associated with sending to two devices, when one of
|
|
them is nc, also causes problems. Even on a sequoia cut&paste does not work
|
|
on the serial interface (stdin=serial) when nc is added to stdout (stdout=
|
|
serial,nc).
|