More info for people.

README

@@ -3,4 +3,79 @@ This is FreeBIOS.
 Requires bcc to compile 16-bit C code.  Obtain bcc from
 ftp://ftp.FreeBSD.org/pub/FreeBSD/ports/distfiles/bcc.tar.gz
 
+Rough directory layout: 
 
+chip is for chipset types. chip/intel is intel mainboards. chip/stpc is
+stpc systems. These are common files to both freebios and linuxbios.
+
+lib is architecture-indepedent (we hope) code that is used by both linuxbios
+and freebios. 
+
+include is what you think. 
+
+----------------------------------------------------
+LinuxBIOS
+-----------------------------------------------------
+linuxbios is the linuxbios directory. Things for linuxbios ONLY live here. 
+
+There is an inflate directory for the inflate code, a lib directory for
+common library code, an include directory, a kernel_patches directory for
+patches to the various kernels, and finally, Makefile.common, an included
+Makefile used by all the builds.
+
+Actual targets are done in caps (this is a Berkeley style thing). 
+In each target are:
+1) crt0.S for that target. These vary a bit by target, although they 
+   do include lots of common code. 
+2) Makefile. This mainly has -D stuff and it includes ../Makefile.common
+3) ldscript.ld. We'd like to make this common, but they seem to vary a lot
+4) linux. (YOU supply this). A soft link to a linux source tree. 
+   e.g. ln -s /usr/src/linux linux
+
+To make this you need a newer GAS. Our version that works is
+
+GNU assembler version 2.9.5 (i386-redhat-linux) using BFD version
+2.9.5.0.22
+
+This comes with redhat 6.2. 
+
+To build, cd to the directory and make, viz. 
+cd linuxbios/PM133
+make
+
+You'll see the various compiles, then you'll see an ld step, then a step
+called mkrom. mkrom builds a 64k linuxbios rom image. Finally the 
+linuxbios 64k image is concatenated with a stripped, compressed linux
+kernel and put into a file called 'romimage'. 
+
+If you say
+make floppy
+it will build it and 'mcopy romimage a:'. This is for those of you with
+FLASH burners. 
+
+-------------------------
+LinuxBIOS structure
+-------------------------
+
+Mkrom puts in a call to f000:fff0, which is the entry point for LinuxBIOS. 
+This starts off in source form in crt0.S
+
+There are about 16 instructions of 16-bit code, in the include file
+../../chip/intel/intel_start32.S. This is the absolute minimum amount of
+assembly code needed. 
+
+This puts us into protected mode with 32-bit addresses. Next ram is turned
+on. We have tried hard to keep the 32-bit assembly to a minimum, and in
+fact what's there is really the little bit needed to get ram going, and
+the other little bit needed to print diagnostic messages to COM1 while RAM
+is set up. If you don't know it already you'll find getting SDRAM going is
+a real mess, though we're getting better at it bit by bit. 
+
+The assembly code calls intel_main function (found in
+../../chip/intel/intel_main.c). This function does all the remaining
+hardware setup in C. Please think hard about adding assembly! We do an
+awful lot in C, include cache, MTRR, MSR, and other setup. 
+
+Finally, intel_main calls linuxbios_main (../inflate/main.c). This code
+unzips the kernel to 0x100000, and jumps to it. From that point on, Linux
+runs the show.