[PATCH 15/19] mc13xxx: mfd_cell is now implicitly available to drivers

On Fri, 4 Feb 2011 10:34:58 +0100
Uwe Kleine-K?nig [off-list ref] wrote:

Hello Andres,

On Wed, Feb 02, 2011 at 08:20:15PM -0800, Andres Salomon wrote:

quoted

No need to explicitly set the cell's platform_data/data_size.

In this case, move the various platform_data pointers
to driver_data.  All of the clients which make use of it
are also changed.

Mfd-core makes a copy of platform_data, but driver_data keeps a
pointer to the original data.  Because each cell's platform_data
previously pointed to a local (stack) variable, the various ARM
mach types that set the pdata are updated to keep the memory around.

I didn't get this even after reading it 5 times.  You wrote in the
subject that drivers now have access to mfd_cell.  I don't see where
e.g. drivers/leds/leds-mc13783.c uses that?!  Does this depend on some
mfd-changes I don't see and this is just a first step?

After reading the changes I think I understood:

 - You made things that were passed as platform_data before available
   via driver_data.

Right.  And as someone pointed out, this doesn't really work as well as
I'd hoped, so I'll have to refine my approach.  Ideally, something
simpler..

 - Because platform_data is copied and driver_data is not at register
   time, the data being platform_data cannot be __initdata or stack
   local anymore, so this needs fixing.

In sum this results in .data becoming bigger (which is bad).

And I think this patch has a conceptual problem, too.  In my opionion
platform_data is the point to hand over platform specific data to a
driver.  driver_data is something that is private to the driver and
has to be considered opaque for the platform.  The driver was sort of
OK before ...

I'll be sending updated patches once I've reworked things.