patch-2.4.0-test12 linux/Documentation/arm/SA1100/serial_UART

• Lines: 66
• Date: Mon Nov 27 17:07:59 2000
• Orig file: v2.4.0-test11/linux/Documentation/arm/SA1100/serial_UART
• Orig date: Wed Dec 31 16:00:00 1969

diff -u --recursive --new-file v2.4.0-test11/linux/Documentation/arm/SA1100/serial_UART linux/Documentation/arm/SA1100/serial_UART
@@ -0,0 +1,65 @@
+The SA1100 serial port finally had its major/minor numbers officially 
+assigned:
+
+> Date: Sun, 24 Sep 2000 21:40:27 -0700
+> From: H. Peter Anvin <hpa@transmeta.com>
+> To: Nicolas Pitre <nico@CAM.ORG>
+> Cc: Device List Maintainer <device@lanana.org>
+> Subject: Re: device
+> 
+> Okay.  Note that device numbers 204 and 205 are used for "low density
+> serial devices", so you will have a range of minors on those majors (the
+> tty device layer handles this just fine, so you don't have to worry about
+> doing anything special.)
+> 
+> So your assignments are:
+> 
+> 204 char        Low-density serial ports
+>                   5 = /dev/ttySA0               SA1100 builtin serial port 0
+>                   6 = /dev/ttySA1               SA1100 builtin serial port 1
+>                   7 = /dev/ttySA2               SA1100 builtin serial port 2
+> 
+> 205 char        Low-density serial ports (alternate device)
+>                   5 = /dev/cusa0                Callout device for ttySA0
+>                   6 = /dev/cusa1                Callout device for ttySA1
+>                   7 = /dev/cusa2                Callout device for ttySA2
+>
+
+So, if you're not using devfs, you must create those inodes in /dev
+on the root filesystem used by your SA1100-based device:
+
+	mknod ttySA0 c 204 5
+	mknod ttySA1 c 204 6
+	mknod ttySA2 c 204 7
+	mknod cusa0 c 205 5
+	mknod cusa1 c 205 6
+	mknod cusa2 c 205 7
+
+Note that the old incorrect use of /dev/ttyS0 in order to use the serial port 
+won't work anymore.  This device node is reserved to the conventionnal 16x50
+UART which may appear on devices like PCMCIA modem, etc.
+
+In addition to the creation of the appropriate device nodes above, you must
+ensure your user space applications make use of the correct device name.
+The classic example is the content of the /etc/inittab where you might have 
+a getty process started on ttyS0.  In this case you have two choices:
+
+1- replace occurences of ttyS0 with ttySA0, ttyS1 with ttySA1, etc.
+
+2- in the occurence of 'ttyS0', you may consider replacing it with 'console'.
+   as in "T0:12345:respawn:/sbin/getty -L console 9600 vt100"
+
+(don't forget to add 'ttySA0', 'console', or the appropriate tty name 
+ in /etc/securetty for root to be allowed to login as well.)
+
+The use of /dev/console has the advantage of being independent of the real
+serial device used.  The kernel automatically forward all operations on
+/dev/console to the apropriate serial device.  The nature of the console may
+also be modified with a kernel command line parameter (see
+Documentation/serial-console.txt for the details).  Of course, 
+/dev/console must have been created as a char device with major 5 minor 1.
+
+Using /dev/console is also compatible with older kernels that used /dev/ttyS0.
+Therefore it is handy for ramdisk images which are targetted for different
+StrongARM platforms and older kernels.
+