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Diffstat (limited to 'Documentation/kbuild/makefiles.txt')
| -rw-r--r-- | Documentation/kbuild/makefiles.txt | 55 |
1 files changed, 40 insertions, 15 deletions
diff --git a/Documentation/kbuild/makefiles.txt b/Documentation/kbuild/makefiles.txt index ab0a984530d..c600e2f44a6 100644 --- a/Documentation/kbuild/makefiles.txt +++ b/Documentation/kbuild/makefiles.txt @@ -45,7 +45,7 @@ This document describes the Linux kernel Makefiles. === 7 Kbuild syntax for exported headers --- 7.1 header-y - --- 7.2 objhdr-y + --- 7.2 genhdr-y --- 7.3 destination-y --- 7.4 generic-y @@ -593,7 +593,7 @@ more details, with real examples. Example: #Makefile - LDFLAGS_vmlinux += $(call really-ld-option, -X) + LDFLAGS_vmlinux += $(call ld-option, -X) === 4 Host Program support @@ -921,8 +921,9 @@ When kbuild executes, the following steps are followed (roughly): Often, the KBUILD_CFLAGS variable depends on the configuration. Example: - #arch/x86/Makefile - cflags-$(CONFIG_M386) += -march=i386 + #arch/x86/boot/compressed/Makefile + cflags-$(CONFIG_X86_32) := -march=i386 + cflags-$(CONFIG_X86_64) := -mcmodel=small KBUILD_CFLAGS += $(cflags-y) Many arch Makefiles dynamically run the target C compiler to @@ -1170,20 +1171,44 @@ When kbuild executes, the following steps are followed (roughly): obvious reason. dtc - Create flattend device tree blob object suitable for linking + Create flattened device tree blob object suitable for linking into vmlinux. Device tree blobs linked into vmlinux are placed in an init section in the image. Platform code *must* copy the blob to non-init memory prior to calling unflatten_device_tree(). - Example: - #arch/x86/platform/ce4100/Makefile - clean-files := *dtb.S + To use this command, simply add *.dtb into obj-y or targets, or make + some other target depend on %.dtb - DTC_FLAGS := -p 1024 - obj-y += foo.dtb.o + A central rule exists to create $(obj)/%.dtb from $(src)/%.dts; + architecture Makefiles do no need to explicitly write out that rule. - $(obj)/%.dtb: $(src)/%.dts - $(call cmd,dtc) + Example: + targets += $(dtb-y) + clean-files += *.dtb + DTC_FLAGS ?= -p 1024 + + dtc_cpp + This is just like dtc as describe above, except that the C pre- + processor is invoked upon the .dtsp file before compiling the result + with dtc. + + In order for build dependencies to work, all files compiled using + dtc_cpp must use the C pre-processor's #include functionality and not + dtc's /include/ functionality. + + Using the C pre-processor allows use of #define to create named + constants. In turn, the #defines will typically appear in a header + file, which may be shared with regular C code. Since the dtc language + represents a data structure rather than code in C syntax, similar + restrictions are placed on a header file included by a device tree + file as for a header file included by an assembly language file. + In particular, the C pre-processor is passed -x assembler-with-cpp, + which sets macro __ASSEMBLY__. __DTS__ is also set. These allow header + files to restrict their content to that compatible with device tree + source. + + A central rule exists to create $(obj)/%.dtb from $(src)/%.dtsp; + architecture Makefiles do no need to explicitly write out that rule. --- 6.8 Custom kbuild commands @@ -1282,15 +1307,15 @@ See subsequent chapter for the syntax of the Kbuild file. Subdirectories are visited before their parent directories. - --- 7.2 objhdr-y + --- 7.2 genhdr-y - objhdr-y specifies generated files to be exported. + genhdr-y specifies generated files to be exported. Generated files are special as they need to be looked up in another directory when doing 'make O=...' builds. Example: #include/linux/Kbuild - objhdr-y += version.h + genhdr-y += version.h --- 7.3 destination-y |