1.\" $NetBSD: console.4,v 1.1 2021/06/03 07:41:26 wiz Exp $ 2.\" 3.Dd September 6, 2006 4.Dt CONS 4 x86 5.Os 6.Sh NAME 7.Nm console 8.Nd x86 console interface 9.Sh SYNOPSIS 10.Cd options CONSDEVNAME=string 11.Cd options CONADDR=integer 12.Cd options CONSPEED=integer 13.Cd options CONS_OVERRIDE 14.Cd options CONMODE=integer 15.Sh DESCRIPTION 16The 17.Dq console 18device is used for 19.Em kernel printf 20messages and accesses to the 21.Pa /dev/console 22character special device in user mode. 23It is attached to a hardware interface at boot time controlled by options 24in the kernel configuration file, or information passed by the boot loader. 25.Pp 26Bootblocks from 27.Nx 1.4 28or newer select their console device from a compiled-in list, 29and then pass their choice of console device and console parameters to 30the kernel. 31.Pp 32As of 33.Nx 1.5 , 34the 35.Ic consdev 36bootblock command allows changing the console device on-the-fly. 37.Pp 38The kernel will use the same console device as the 39bootblock; no special kernel configuration is required. 40.Pp 41To override 42the bootblock's choice of console, or to use a serial kernel console 43with older bootblocks, you must specify kernel config-file options to 44override the information passed by the bootblock. 45The current option choices are: 46.Bl -tag -width aaa 47.It - the standard PC keyboard and display 48(with either the 49.Dq pc 50or the 51.Xr wscons 4 52driver) 53.It - standard PC serial ports 54(with 55.Xr com 4 56driver) 57.El 58.Pp 59The available 60.Em kernel configuration 61options are: 62.Bl -ohang 63.It Cd options CONSDEVNAME=string 64specifies the name of the console device. 65Valid values are 66.Dq pc 67for the pc keyboard / display (default) 68and 69.Dq com 70for a serial port. 71.It Cd options CONADDR=integer 72sets the base address for the serial console port (default: 0x3f8). 73.It Cd options CONSPEED=integer 74sets the baudrate for the serial console (default: 9600). 75.It Cd options CONS_OVERRIDE 76causes console information passed by the bootloader to be ignored and 77the settings specified by the three options above (or the defaults) to be 78used. 79Default behaviour is to use the settings from the bootloader if 80present, and to use option / default values only if no information was 81passed. 82.It Cd options CONMODE=integer 83allows to specify terminal control flags. 84The argument is a 85.Dq cflag 86value, see 87.Xr termios 4 88for details. 89Default is 90.Li ( CREAD | CS8 | HUPCL ) 91(8N1). 92This option takes always effect, because mode settings are not passed 93by the bootloader. 94.El 95.Sh FILES 96.Bl -tag -width /dev/console 97.It Pa /dev/console 98.El 99.Sh EXAMPLES 100.Cd options CONSDEVNAME=\&"\e"com\e"\&",CONADDR=0x2f8,CONSPEED=57600 101.Sh SEE ALSO 102.Xr config 1 , 103.Xr tty 4 , 104.Xr boot 8 105.Sh BUGS 106The console device is chosen early in system startup regardless 107if the specified driver / device is present in the system configuration file. 108If the driver asked for by the bootloader or 109.Dq Cd options CONSDEVNAME 110is not configured into the system, a panic is caused. 111Because there is 112no console device, no explaining message will be printed. 113If the driver is present, but the specific device instance not, kernel 114printf will work, but 115.Pa /dev/console 116becomes a dummy. 117