sh: Update new-machine.txt so it's more accurate.

        |

	.. more boards here ...

It should also be noted that each board is required to have some certain

headers. At the time of this writing, io.h is the only thing that needs

to be provided for each board, and can generally just reference generic

functions (with the exception of isa_port2addr).

Next, for companion chips:

.

`-- arch

Both the Solution Engine and the hp6xx boards are an example of this.

After you have setup your new arch/sh/boards/ directory, remember that you

also must add a directory in include/asm-sh for headers localized to this

board. In order to interoperate seamlessly with the build system, it's best

to have this directory the same as the arch/sh/boards/ directory name,

though if your board is again part of a family, the build system has ways

of dealing with this, and you can feel free to name the directory after

the family member itself.

should also add a directory in include/asm-sh for headers localized to this

board (if there are going to be more than one). In order to interoperate

seamlessly with the build system, it's best to have this directory the same

as the arch/sh/boards/ directory name, though if your board is again part of

a family, the build system has ways of dealing with this (via incdir-y

overloading), and you can feel free to name the directory after the family

member itself.

There are a few things that each board is required to have, both in the

arch/sh/boards and the include/asm-sh/ heirarchy. In order to better

 * arch/sh/boards/vapor/setup.c - Setup code for imaginary board

 */

#include <linux/init.h>

#include <asm/rtc.h> /* for board_time_init() */

const char *get_system_type(void)

{

}

Our new imaginary board will also have to tie into the machvec in order for it

to be of any use. Currently the machvec is slowly on its way out, but is still

required for the time being. As such, let us take a look at what needs to be

done for the machvec assignment.

to be of any use.

machvec functions fall into a number of categories:

 - I/O functions to IO memory (inb etc) and PCI/main memory (readb etc).

 - I/O remapping functions (ioremap etc)

 - some initialisation functions

 - a 'heartbeat' function

 - some miscellaneous flags

The tree can be built in two ways:

 - as a fully generic build. All drivers are linked in, and all functions

   go through the machvec

 - as a machine specific build. In this case only the required drivers

   will be linked in, and some macros may be redefined to not go through

   the machvec where performance is important (in particular IO functions).

There are three ways in which IO can be performed:

 - none at all. This is really only useful for the 'unknown' machine type,

   which us designed to run on a machine about which we know nothing, and

   so all all IO instructions do nothing.

 - fully custom. In this case all IO functions go to a machine specific

   set of functions which can do what they like

 - a generic set of functions. These will cope with most situations,

   and rely on a single function, mv_port2addr, which is called through the

   machine vector, and converts an IO address into a memory address, which

   can be read from/written to directly.

Thus adding a new machine involves the following steps (I will assume I am

adding a machine called vapor):

 - add a new file include/asm-sh/vapor/io.h which contains prototypes for

 - I/O mapping functions (ioport_map, ioport_unmap, etc).

 - a 'heartbeat' function.

 - PCI and IRQ initialization routines.

 - Consistent allocators (for boards that need special allocators,

   particularly for allocating out of some board-specific SRAM for DMA

   handles).

There are machvec functions added and removed over time, so always be sure to

consult include/asm-sh/machvec.h for the current state of the machvec.

The kernel will automatically wrap in generic routines for undefined function

pointers in the machvec at boot time, as machvec functions are referenced

unconditionally throughout most of the tree. Some boards have incredibly

sparse machvecs (such as the dreamcast and sh03), whereas others must define

virtually everything (rts7751r2d).

Adding a new machine is relatively trivial (using vapor as an example):

If the board-specific definitions are quite minimalistic, as is the case for

the vast majority of boards, simply having a single board-specific header is

sufficient.

 - add a new file include/asm-sh/vapor.h which contains prototypes for

   any machine specific IO functions prefixed with the machine name, for

   example vapor_inb. These will be needed when filling out the machine

   vector.

   This is the minimum that is required, however there are ample

   opportunities to optimise this. In particular, by making the prototypes

   inline function definitions, it is possible to inline the function when

   building machine specific versions. Note that the machine vector

   functions will still be needed, so that a module built for a generic

   setup can be loaded.

   Note that these prototypes are generated automatically by setting

   __IO_PREFIX to something sensible. A typical example would be:

 - add a new file arch/sh/boards/vapor/mach.c. This contains the definition

   of the machine vector. When building the machine specific version, this

   will be the real machine vector (via an alias), while in the generic

   version is used to initialise the machine vector, and then freed, by

   making it initdata. This should be defined as:

	#define __IO_PREFIX vapor

   	#include <asm/io_generic.h>

   somewhere in the board-specific header. Any boards being ported that still

   have a legacy io.h should remove it entirely and switch to the new model.

 - Add machine vector definitions to the board's setup.c. At a bare minimum,

   this must be defined as something like:

	struct sh_machine_vector mv_vapor __initmv = {

		.mv_name = "vapor",

     }

	};

	ALIAS_MV(vapor)

 - finally add a file arch/sh/boards/vapor/io.c, which contains

   definitions of the machine specific io functions.

A note about initialisation functions. Three initialisation functions are

provided in the machine vector:

 - mv_arch_init - called very early on from setup_arch

 - mv_init_irq - called from init_IRQ, after the generic SH interrupt

   initialisation

 - mv_init_pci - currently not used

Any other remaining functions which need to be called at start up can be

added to the list using the __initcalls macro (or module_init if the code

can be built as a module). Many generic drivers probe to see if the device

they are targeting is present, however this may not always be appropriate,

so a flag can be added to the machine vector which will be set on those

machines which have the hardware in question, reducing the probe to a

single conditional.

 - finally add a file arch/sh/boards/vapor/io.c, which contains definitions of

   the machine specific io functions (if there are enough to warrant it).

3. Hooking into the Build System

================================

oldconfig (prompting you for any new options since the time of creation),

and start you on your way to having a functional kernel for your new

board.