mach header files

[Grant Likely]

On Fri, Apr 4, 2014 at 5:16 AM, Phil Edworthy <phil.edworthy at renesas.com> wrote:
> 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?

If it is used only by one driver, then it should go directly into that
driver without a #include. For SoC defines, you'll need to check with
the arm-soc maintainers. I *think* we're trying to get away from
separate arch/arm/mach-* directories, but I'm slightly out of touch.
You certainly should not do anything that breaks multiplatform builds.

g.