xref: /openbmc/u-boot/doc/README.silent (revision d66ff4ba)
1The config option CONFIG_SILENT_CONSOLE can be used to quiet messages
2on the console.  If the option has been enabled, the output can be
3silenced by setting the environment variable "silent".
4
5- CONFIG_SILENT_CONSOLE_UPDATE_ON_SET
6	When the "silent" variable is changed with env set, the change
7	will take effect immediately.
8
9- CONFIG_SILENT_CONSOLE_UPDATE_ON_RELOC
10	Some environments are not available until relocation (e.g. NAND)
11	so this will make the value in the flash env take effect at
12	relocation.
13
14The following actions are taken if "silent" is set at boot time:
15
16 - Until the console devices have been initialized, output has to be
17   suppressed by testing for the flag "GD_FLG_SILENT" in "gd->flags".
18
19 - When the console devices have been initialized, "stdout" and
20   "stderr" are set to "nulldev", so subsequent messages are
21   suppressed automatically. Make sure to enable "nulldev" by
22   #defining CONFIG_SYS_DEVICE_NULLDEV in your board config file.
23
24 - When booting a linux kernel, the "bootargs" are fixed up so that
25   the argument "console=" will be in the command line, no matter how
26   it was set in "bootargs" before. If you don't want the linux command
27   line to be affected, define CONFIG_SILENT_U_BOOT_ONLY in your board
28   config file as well, and this part of the feature will be disabled.
29