mach header files

[Phil Edworthy]

Hi Grant,

On: 04 April 2014 11:30, Grant wrote:
> On Fri, Apr 4, 2014 at 1:19 AM, Phil Edworthy <phil.edworthy at renesas.com>
> wrote:
> > Resent, hopefully without the automatic corporate signature appended
> this time...
> >
> > Hi,
> >
> > I am porting the kernel to a new device, for which I've created a new
> arch/arm/mach-... directory, and I also a clock driver that lives under
> driver/clk. Everything is all working fine, though I am now cleaning up the
> code and have a question about mach specific header files.
> >
> > The clock driver is completely specific to this device, but needs to read from
> a system register (just for external boot mode pins) to determine some PLL
> settings. This register is in a block of system registers which are also used by
> the mach code in arch/arm/mach-...
> >
> > Since the clock driver is specific to the mach, is there any point in specifying
> the address of this reg in the corresponding dtsi? The format and
> functionality described by this register would not be the same on any other
> device.
> 
> Why would you not? The dts is a central place where the entire memory map
> layout of the device can be specified. If I were working on the board support,
> I would create a node for the register block and have the driver retrieve that
> node.

Ok, that's a slightly different view to the one I had. I had thought that the dts would only contain information that could be changed from one platform to another.

> > If I don't specify the address of the register in the dtsi, I think it would be
> best to have a common header file for all of the system registers. I've seen
> some drivers, e.g.  exynos-cpufreq.c, doing this by including files from mach-
> exynos/include/mach. Is that the right way to do this?
> 
> You'd still want to have a header file for each of the register offsets within
> the block. You wouldn't want to itemize register offsets in the device tree
> node.

You would put that include file in a mach-.../include/mach/ dir, right?

Thanks
Phil