Document comconsole_port and comconsole_pcidev loader variables.

MFC after:	2 weeks

1 files changed, 38 insertions, 1 deletions

diff --git a/sys/boot/common/loader.8 b/sys/boot/common/loader.8
index 43588ab..6c027ff 100644
--- a/sys/boot/common/loader.8
+++ b/sys/boot/common/loader.8
@@ -24,7 +24,7 @@
 .\"
 .\" $FreeBSD$
 .\"
-.Dd December 27, 2011
+.Dd January 7, 2012
 .Dt LOADER 8
 .Os
 .Sh NAME
@@ -419,6 +419,43 @@ was compiled.
 Changes to the
 .Va comconsole_speed
 variable take effect immediately.
+.It Va comconsole_port
+Defines the base i/o port used to access console UART
+(i386 and amd64 only).
+If the variable is not set, its assumed value is 0x3F8, which
+corresponds to PC port COM1, unless overriden by
+.Va BOOT_COMCONSOLE_PORT
+variable during the compilation of
+.Nm .
+Setting the
+.Va comconsole_port
+variable automatically set
+.Va hw.uart.console
+environment variable to provide a hint to kernel for location of the console.
+Loader console is changed immediately after variable
+.Va comconsole_port
+is set.
+.It Va comconsole_pcidev
+Defines the location of a PCI device of the 'simple communication'
+class to be used as the serial console UART (i386 and amd64 only).
+The syntax of the variable is
+.Li 'bus:device:function[:bar]' ,
+where all members must be numeric, with possible
+.Li 0x
+prefix to indicate a hexadecimal value.
+The
+.Va bar
+member is optional and assumed to be 0x10 if omitted.
+The bar must decode i/o space.
+Setting the variable
+.Va comconsole_pcidev
+automatically sets the variable
+.Va comconsole_port
+to the base of the selected bar, and hint
+.Va hw.uart.console .
+Loader console is changed immediately after variable
+.Va comconsole_pcidev
+is set.
 .It Va console
 Defines the current console or consoles.
 Multiple consoles may be specified.