Re: [PATCH] extend physmap.c to support run-time adding partitions

[Jun Sun <jsun@mvista.com>]

On Thu, Oct 23, 2003 at 05:33:07PM +0200, Jörn Engel wrote:
> On Wed, 22 October 2003 18:25:58 -0700, Jun Sun wrote:
> > 
> > While looking at drvers/mtd/maps directories, it becomes
> > obvious to me that many files are derived from physmap.c,
> > in order to add partition support or add their own
> > set_vpp() pointer, etc..
> > 
> > Such a need can be easily satisfied by extending physmap.c
> > a little.
> > 
> > In this patch, I like to introduce phsmap_add_partition()
> > function, which allows boards to add flash partitions
> > at run-time.  (Note that you can still override this
> > hardcoded partition by using kernel command line)
> > 
> > In the patch I also showed how a board can make use of this
> > extension.  Hopefully we can get rid of lots of files under 
> > the maps directory. :)
> 
> For most people, you saved source code size and wasted binary size.
> The very same people are far more concerned about binary size. :)
>

Ahh, note that I turned a couple of functions and data into
__init kind.  That should make space-conservative people happy.
 
> I've tried to clean this up before and failed, but maybe you can do a
> better job.  Good luck!
>

What was the main objection?  I can list quite a few benefits:

1. remove _lots_ of duplicated mapping files, which also means
   a cleaner CONFIG_xxx space and a simpler Makefile.
2. the board-specific partition setup is now done in arch/<xxx>/<board>/setup.c
   which means when a board is deleted, its flash support is automatically
   removed.  (Not so with current arrangement)
3. futher _common_ improvement is possible.  For example, for most MIPS boards
   we don't need ioremap to access the flash area - CPU has a fixed uncached
   mapping to physical space.  Now we can just modify one file and benefts
   about almost 20 boards.

Jun