[people/ms/u-boot.git] / doc / README.silent

The config option CONFIG_SILENT_CONSOLE can be used to quiet messages
on the console.  If the option has been enabled, the output can be
silenced by setting the environment variable "silent".

- CONFIG_SILENT_CONSOLE_UPDATE_ON_SET
	When the "silent" variable is changed with env set, the change
	will take effect immediately.

- CONFIG_SILENT_CONSOLE_UPDATE_ON_RELOC
	Some environments are not available until relocation (e.g. NAND)
	so this will make the value in the flash env take effect at
	relocation.

The following actions are taken if "silent" is set at boot time:

 - Until the console devices have been initialized, output has to be
   suppressed by testing for the flag "GD_FLG_SILENT" in "gd->flags".

 - When the console devices have been initialized, "stdout" and
   "stderr" are set to "nulldev", so subsequent messages are
   suppressed automatically. Make sure to enable "nulldev" by
   #defining CONFIG_SYS_DEVICE_NULLDEV in your board config file.

 - When booting a linux kernel, the "bootargs" are fixed up so that
   the argument "console=" will be in the command line, no matter how
   it was set in "bootargs" before. If you don't want the linux command
   line to be affected, define CONFIG_SILENT_U_BOOT_ONLY in your board
   config file as well, and this part of the feature will be disabled.
Commit	Line	Data
f72da340 WD	1	The config option CONFIG_SILENT_CONSOLE can be used to quiet messages
f72da340 WD	2	on the console. If the option has been enabled, the output can be
e080d545 JH	3	silenced 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.
f72da340 WD	13
	14	The 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".
f72da340 WD	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
6d0f6bcf	22	#defining CONFIG_SYS_DEVICE_NULLDEV in your board config file.
f72da340 WD	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
be2e5a09 JH	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.