[PATCH 2/5] Description of _shipped files handling in kbuild

[Nicholas Mc Guire]

Description of _shipped files handling in kbuild

This adds a section on handling of _shipped files in Kbuild
Makefiles and the build process.

This patch is against linux 3.18.0-rc6

Signed-off-by: Nicholas Mc Guire <der.herr@xxxxxxx>
---
 Documentation/kbuild/makefiles.txt |   58 +++++++++++++++++++++++++++++++++++-
 1 file changed, 57 insertions(+), 1 deletion(-)

diff --git a/Documentation/kbuild/makefiles.txt b/Documentation/kbuild/makefiles.txt
index a311db8..df3a96a 100644
--- a/Documentation/kbuild/makefiles.txt
+++ b/Documentation/kbuild/makefiles.txt
@@ -19,6 +19,7 @@ This document describes the Linux kernel Makefiles.
 	   --- 3.10 Special Rules
 	   --- 3.11 $(CC) support functions
 	   --- 3.12 $(LD) support functions
+	   --- 3.13 _shipped - generated files
 
 	=== 4 Host Program support
 	   --- 4.1 Simple Host Program
@@ -594,6 +595,61 @@ more details, with real examples.
 		#Makefile
 		LDFLAGS_vmlinux += $(call ld-option, -X)
 
+--- 3.13 _shipped - generated files
+
+   Some sources in the kernel are generated by tools or special
+   purpose scripts so that the build process dependencies can be kept
+   at a reasonable level. Also in cases where the translation is not
+   configuration dependent but might impact build time, _shipped files
+   may be added along with the actual sources to speed up the build
+   process.
+
+   For standard tools like lex and yacc the make process will actually
+   generate the _shipped files (see scripts/Makefile.lib) and retain
+   them by marking them .PRECIOUS so they are not removed by the clean
+   targets.
+
+   For non-standard tools the generation of the _shipped file itself
+   may be manually achieved by building and then renaming. A makefile
+   target to generate the actual target file should to be provided
+   though and can be conditioned on an environment variable.
+
+	Example:
+		ifdef GENERATE_KEYMAP
+
+		$(obj)/defkeymap.c: $(obj)/%.c: $(src)/%.map
+			loadkeys --mktable $< > $@
+
+		endif
+
+   The _shipped file does not appear in the actual Makefile, this is
+   handled by the rules found in scripts/Makefile.lib.
+
+		<snip>
+		cmd_shipped = cat $< > $@
+
+		$(obj)/%: $(src)/%_shipped
+			$(call cmd,shipped)
+		<snip>
+
+   which simply will copy the target_shipped to the target
+
+   If a file of a make target is found in the build directory with the
+   extension _shipped, make will use it rather than generating the
+   respective target file from source.
+
+   The build will indicate the use of the _shipped file by the SHIPPED
+   quiet command in the make output.
+
+	Example:
+		LD      drivers/scsi/aic7xxx/built-in.o
+		SHIPPED drivers/scsi/aic7xxx/aic79xx_seq.h
+		SHIPPED drivers/scsi/aic7xxx/aic79xx_reg.h
+		CC [M]  drivers/scsi/aic7xxx/aic79xx_core.o
+		CC [M]  drivers/scsi/aic7xxx/aic79xx_pci.o
+		SHIPPED drivers/scsi/aic7xxx/aic79xx_reg_print.c
+		CC [M]  drivers/scsi/aic7xxx/aic79xx_reg_print.o
+
 
 === 4 Host Program support
 
@@ -1399,10 +1455,10 @@ Original version made by Michael Elizabeth Chastain, <mailto:mec@xxxxxxxxx>
 Updates by Kai Germaschewski <kai@xxxxxxxxxxxxxxxxxxxxxx>
 Updates by Sam Ravnborg <sam@xxxxxxxxxxxx>
 Language QA by Jan Engelhardt <jengelh@xxxxxx>
+Kbuild support for shipped files Nicholas Mc Guire <der.herr@xxxxxxx>
 
 === 11 TODO
 
-- Describe how kbuild supports shipped files with _shipped.
 - Generating offset header files.
 - Add more variables to section 7?
 
-- 
1.7.10.4

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