On 02/20/2013 09:37 PM, Shawn Guo wrote: > On Wed, Feb 20, 2013 at 02:05:56PM -0700, Stephen Warren wrote: >> From: Stephen Warren <swarren@xxxxxxxxxx> >> >> The recent dtc+cpp support allows header files and C pre-processor >> defines/macros to be used when compiling device tree files. These >> headers will typically define various constants that are part of the >> device tree bindings. >> >> The original patch which set up the dtc+cpp include path only considered >> using those headers from device tree files. However, they are also >> useful for kernel code which needs to interpret the device tree. >> >> In both the DT files and the kernel, I'd like to include the DT-related >> headers in the same way, for example, <dt-bindings/gpio/tegra-gpio.h>. >> That will simplify any text which discusses the DT header locations. >> >> Creating a <dt-bindings/> for kernel source to use is as simple as >> placing files into include/dt-bindings/. >> >> However, when compiling DT files, the include path should be restricted >> so that only the dt-bindings path is available; arbitrary kernel headers >> shouldn't be exposed. For this reason, create a specific include >> directory for use by dtc+cpp, and symlink dt-bindings from there to the >> actual location of include/dt-bindings/. For want of a better location, >> place this "include chroot" into the existing dts/ directory. >> >> arch/*/boot/dts/include/dt-bindings -> ../../../../../dt-bindings > > ../../../../../include/dt-bindings Yup. > And, I would expect only the headers that will actually be referenced > by kernel should go into include/dt-bindings. There is no point to > put headers that will not be included by kernel but only by dts files > into there, and instead arch/arm/boot/dts/include should just be good > enough for them. With this agreed ... There are two things that include DT-related headers: a) Device trees (*.dts, *.dtsi) b) The kernel All the headers relevant here fall into category (a) by definition. I'd actually expect most to also fall into category (b), although I can see that category (b) might be a strict subset of category (a). I believe you're proposing only storing category (b) headers in include/dt-bindings/, and storing any others I suppose in arch/*/boot/dts/. But, my thoughts are that /all/ these headers (both categories) should be stored in one place for consistency. That way, if/when the DT binding docs, these headers, and the DT files themselves move out of the kernel, we'll end up with some other repository/repositories that might have the following top-level directories (or at least these sets of logical data): 1) DT binding documents 2) Headers that define constants for (1) 3) DT files (*.dts/*.dtsi) We need at least some of (2) in the kernel for drivers to share the constant definitions, so my proposal is to simply copy /all/ the headers from (2) into the kernel's include/dt-bindings/. That keeps things simple; simply copy everything and maintain the same hierarchy under that "root" directory. Otherwise, we'll be constantly wondering which headers to copy, perhaps moving things back/forth as people realize that the kernel needs them, etc. -- To unsubscribe from this list: send the line "unsubscribe linux-kbuild" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
