kbuild: Introduce hostprogs-y, deprecate host-progs

Introducing hostprogs-y allows a user to use the typical Kbuild
pattern in a Kbuild file:
hostprogs-$(CONFIG_KALLSYMS) += ...

And then during cleaning the referenced file are still deleted.
Deprecate the old host-progs assignment but kept the functionlity.

External modules will continue to use host-progs for a while - drawback is
that they now see a warning.
Workaround - just assign both variables:
hostprogs-y := foo
host-progs  := $(hostprogs-y)

All in-kernel users will be converted in next patch.
Signed-off-by: Sam Ravnborg <sam@ravnborg.org>

Documentation/kbuild/makefiles.txt

@@ -25,6 +25,7 @@ This document describes the Linux kernel Makefiles.
 	   --- 4.4 Using C++ for host programs
 	   --- 4.5 Controlling compiler options for host programs
 	   --- 4.6 When host programs are actually built
+	   --- 4.7 Using hostprogs-$(CONFIG_FOO)
 
 	=== 5 Kbuild clean infrastructure
 
@@ -387,7 +388,7 @@ compilation stage.
 Two steps are required in order to use a host executable.
 
 The first step is to tell kbuild that a host program exists. This is
-done utilising the variable host-prog.
+done utilising the variable hostprogs-y.
 
 The second step is to add an explicit dependency to the executable.
 This can be done in two ways. Either add the dependency in a rule, 
@@ -402,7 +403,7 @@ Both possibilities are described in the following.
 	built on the build host.
 
 	Example:
-		host-progs := bin2hex
+		hostprogs-y := bin2hex
 
 	Kbuild assumes in the above example that bin2hex is made from a single
 	c-source file named bin2hex.c located in the same directory as
@@ -418,7 +419,7 @@ Both possibilities are described in the following.
 
 	Example:
 		#scripts/lxdialog/Makefile
-		host-progs    := lxdialog  
+		hostprogs-y   := lxdialog  
 		lxdialog-objs := checklist.o lxdialog.o
 
 	Objects with extension .o are compiled from the corresponding .c
@@ -438,7 +439,7 @@ Both possibilities are described in the following.
 
 	Example:
 		#scripts/kconfig/Makefile
-		host-progs      := conf
+		hostprogs-y     := conf
 		conf-objs       := conf.o libkconfig.so
 		libkconfig-objs := expr.o type.o
   
@@ -457,7 +458,7 @@ Both possibilities are described in the following.
 
 	Example:
 		#scripts/kconfig/Makefile
-		host-progs    := qconf
+		hostprogs-y   := qconf
 		qconf-cxxobjs := qconf.o
 
 	In the example above the executable is composed of the C++ file
@@ -468,7 +469,7 @@ Both possibilities are described in the following.
 
 	Example:
 		#scripts/kconfig/Makefile
-		host-progs    := qconf
+		hostprogs-y   := qconf
 		qconf-cxxobjs := qconf.o
 		qconf-objs    := check.o
 	
@@ -509,7 +510,7 @@ Both possibilities are described in the following.
 
 	Example:
 		#drivers/pci/Makefile
-		host-progs := gen-devlist
+		hostprogs-y := gen-devlist
 		$(obj)/devlist.h: $(src)/pci.ids $(obj)/gen-devlist
 			( cd $(obj); ./gen-devlist ) < $<
 
@@ -524,18 +525,32 @@ Both possibilities are described in the following.
 
 	Example:
 		#scripts/lxdialog/Makefile
-		host-progs    := lxdialog
-		always        := $(host-progs)
+		hostprogs-y   := lxdialog
+		always        := $(hostprogs-y)
 
 	This will tell kbuild to build lxdialog even if not referenced in
 	any rule.
 
+--- 4.7 Using hostprogs-$(CONFIG_FOO)
+
+	A typcal pattern in a Kbuild file lok like this:
+
+	Example:
+		#scripts/Makefile
+		hostprogs-$(CONFIG_KALLSYMS) += kallsyms
+
+	Kbuild knows about both 'y' for built-in and 'm' for module.
+	So if a config symbol evaluate to 'm', kbuild will still build
+	the binary. In other words Kbuild handle hostprogs-m exactly
+	like hostprogs-y. But only hostprogs-y is recommend used
+	when no CONFIG symbol are involved.
+
 === 5 Kbuild clean infrastructure
 
 "make clean" deletes most generated files in the src tree where the kernel
 is compiled. This includes generated files such as host programs.
-Kbuild knows targets listed in $(host-progs), $(always), $(extra-y) and
-$(targets). They are all deleted during "make clean".
+Kbuild knows targets listed in $(hostprogs-y), $(hostprogs-m), $(always),
+$(extra-y) and $(targets). They are all deleted during "make clean".
 Files matching the patterns "*.[oas]", "*.ko", plus some additional files
 generated by kbuild are deleted all over the kernel src tree when
 "make clean" is executed.

scripts/Makefile.build

@@ -14,8 +14,13 @@ include $(obj)/Makefile
 
 include scripts/Makefile.lib
 
-# Do not include host-progs rules unles needed
 ifdef host-progs
+$(warning kbuild: $(obj)/Makefile - Usage of host-progs is deprecated. Please replace with hostprogs-y!)
+hostprogs-y += $(host-progs)
+endif
+
+# Do not include host rules unles needed
+ifneq ($(hostprogs-y)$(hostprogs-m),)
 include scripts/Makefile.host
 endif
 

scripts/Makefile.clean

@@ -29,8 +29,10 @@ subdir-ymn      := $(sort $(subdir-ym) $(subdir-n) $(subdir-))
 # Add subdir path
 
 subdir-ymn	:= $(addprefix $(obj)/,$(subdir-ymn))
-__clean-files	:= $(extra-y) $(EXTRA_TARGETS) $(always) $(host-progs) \
-		   $(targets) $(clean-files)
+__clean-files	:= $(extra-y) $(EXTRA_TARGETS) $(always) \
+		   $(targets) $(clean-files)             \
+		   $(host-progs)                         \
+		   $(hostprogs-y) $(hostprogs-m) $(hostprogs-)
 __clean-files   := $(wildcard                                               \
                    $(addprefix $(obj)/, $(filter-out /%, $(__clean-files))) \
 		   $(filter /%, $(__clean-files)))

scripts/Makefile.host

@@ -6,21 +6,21 @@
 # Both C and C++ is supported, but preferred language is C for such utilities.
 #
 # Samle syntax (see Documentation/kbuild/makefile.txt for reference)
-# host-progs := bin2hex
+# hostprogs-y := bin2hex
 # Will compile bin2hex.c and create an executable named bin2hex
 #
-# host-progs    := lxdialog
+# hostprogs-y    := lxdialog
 # lxdialog-objs := checklist.o lxdialog.o
 # Will compile lxdialog.c and checklist.c, and then link the executable
 # lxdialog, based on checklist.o and lxdialog.o
 #
-# host-progs      := qconf
+# hostprogs-y      := qconf
 # qconf-cxxobjs   := qconf.o
 # qconf-objs      := menu.o
 # Will compile qconf as a C++ program, and menu as a C program.
 # They are linked as C++ code to the executable qconf
 
-# host-progs := conf
+# hostprogs-y := conf
 # conf-objs  := conf.o libkconfig.so
 # libkconfig-objs := expr.o type.o
 # Will create a shared library named libkconfig.so that consist of
@@ -30,26 +30,28 @@
 # libkconfig.so as the executable conf.
 # Note: Shared libraries consisting of C++ files are not supported
 
-# host-progs := tools/build may have been specified. Retreive directory
-obj-dirs += $(foreach f,$(host-progs), $(if $(dir $(f)),$(dir $(f))))
+__hostprogs := $(hostprogs-y)$(hostprogs-m)
+
+# hostprogs-y := tools/build may have been specified. Retreive directory
+obj-dirs += $(foreach f,$(__hostprogs), $(if $(dir $(f)),$(dir $(f))))
 obj-dirs := $(strip $(sort $(filter-out ./,$(obj-dirs))))
 
 
 # C code
 # Executables compiled from a single .c file
-host-csingle	:= $(foreach m,$(host-progs),$(if $($(m)-objs),,$(m)))
+host-csingle	:= $(foreach m,$(__hostprogs),$(if $($(m)-objs),,$(m)))
 
 # C executables linked based on several .o files
-host-cmulti	:= $(foreach m,$(host-progs),\
+host-cmulti	:= $(foreach m,$(__hostprogs),\
 		   $(if $($(m)-cxxobjs),,$(if $($(m)-objs),$(m))))
 
 # Object (.o) files compiled from .c files
-host-cobjs	:= $(sort $(foreach m,$(host-progs),$($(m)-objs)))
+host-cobjs	:= $(sort $(foreach m,$(__hostprogs),$($(m)-objs)))
 
 # C++ code
 # C++ executables compiled from at least on .cc file
 # and zero or more .c files
-host-cxxmulti	:= $(foreach m,$(host-progs),$(if $($(m)-cxxobjs),$(m)))
+host-cxxmulti	:= $(foreach m,$(__hostprogs),$(if $($(m)-cxxobjs),$(m)))
 
 # C++ Object (.o) files compiled from .cc files
 host-cxxobjs	:= $(sort $(foreach m,$(host-cxxmulti),$($(m)-cxxobjs)))
@@ -63,7 +65,7 @@ host-cobjs	:= $(filter-out %.so,$(host-cobjs))
 #Object (.o) files used by the shared libaries
 host-cshobjs	:= $(sort $(foreach m,$(host-cshlib),$($(m:.so=-objs))))
 
-host-progs      := $(addprefix $(obj)/,$(host-progs))
+__hostprogs     := $(addprefix $(obj)/,$(__hostprogs))
 host-csingle	:= $(addprefix $(obj)/,$(host-csingle))
 host-cmulti	:= $(addprefix $(obj)/,$(host-cmulti))
 host-cobjs	:= $(addprefix $(obj)/,$(host-cobjs))