Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1 | ### |
| 2 | # This makefile is used to generate the kernel documentation, |
| 3 | # primarily based on in-line comments in various source files. |
| 4 | # See Documentation/kernel-doc-nano-HOWTO.txt for instruction in how |
Adrian Bunk | 58ef2c4 | 2006-04-01 01:04:59 +0200 | [diff] [blame] | 5 | # to document the SRC - and how to read it. |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 6 | # To add a new book the only step required is to add the book to the |
| 7 | # list of DOCBOOKS. |
| 8 | |
Paul Gortmaker | bb8187d | 2012-05-17 19:06:13 -0400 | [diff] [blame] | 9 | DOCBOOKS := z8530book.xml device-drivers.xml \ |
Jeff Garzik | ac9296f | 2005-05-01 08:59:27 -0700 | [diff] [blame] | 10 | kernel-hacking.xml kernel-locking.xml deviceiobook.xml \ |
Alexey Dobriyan | 82c1e49 | 2009-12-15 16:46:59 -0800 | [diff] [blame] | 11 | writing_usb_driver.xml networking.xml \ |
Jason Wessel | e3e2aaf | 2008-03-20 13:43:45 -0500 | [diff] [blame] | 12 | kernel-api.xml filesystems.xml lsm.xml usb.xml kgdb.xml \ |
Thomas Gleixner | 11c869e | 2006-06-29 02:24:47 -0700 | [diff] [blame] | 13 | gadget.xml libata.xml mtdnand.xml librs.xml rapidio.xml \ |
Johannes Berg | dbbea67 | 2008-02-26 14:34:06 +0100 | [diff] [blame] | 14 | genericirq.xml s390-drivers.xml uio-howto.xml scsi.xml \ |
Johannes Berg | 352de557 | 2010-08-17 12:04:34 +0200 | [diff] [blame] | 15 | 80211.xml debugobjects.xml sh.xml regulator.xml \ |
Jason Baron | a76f8c6 | 2009-04-30 13:29:42 -0400 | [diff] [blame] | 16 | alsa-driver-api.xml writing-an-alsa-driver.xml \ |
Daniel Vetter | 3a4579b | 2015-10-07 09:55:28 +0200 | [diff] [blame] | 17 | tracepoint.xml gpu.xml media_api.xml w1.xml \ |
Daniel Baluta | aab9787 | 2015-08-04 17:20:08 +0300 | [diff] [blame] | 18 | writing_musb_glue_layer.xml crypto-API.xml iio.xml |
Mauro Carvalho Chehab | 4266129 | 2011-05-31 16:27:44 -0300 | [diff] [blame] | 19 | |
Kevin Hao | b12f737 | 2014-04-01 14:36:10 +0800 | [diff] [blame] | 20 | include Documentation/DocBook/media/Makefile |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 21 | |
| 22 | ### |
| 23 | # The build process is as follows (targets): |
Randy Dunlap | 2ac534b | 2007-07-19 01:48:23 -0700 | [diff] [blame] | 24 | # (xmldocs) [by docproc] |
| 25 | # file.tmpl --> file.xml +--> file.ps (psdocs) [by db2ps or xmlto] |
| 26 | # +--> file.pdf (pdfdocs) [by db2pdf or xmlto] |
| 27 | # +--> DIR=file (htmldocs) [by xmlto] |
| 28 | # +--> man/ (mandocs) [by xmlto] |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 29 | |
Martin Waitz | 71f95cf | 2005-11-13 16:08:15 -0800 | [diff] [blame] | 30 | |
| 31 | # for PDF and PS output you can choose between xmlto and docbook-utils tools |
| 32 | PDF_METHOD = $(prefer-db2x) |
| 33 | PS_METHOD = $(prefer-db2x) |
| 34 | |
| 35 | |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 36 | ### |
| 37 | # The targets that may be used. |
Mauro Carvalho Chehab | 4266129 | 2011-05-31 16:27:44 -0300 | [diff] [blame] | 38 | PHONY += xmldocs sgmldocs psdocs pdfdocs htmldocs mandocs installmandocs cleandocs |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 39 | |
Masahiro Yamada | 6f89b9c | 2014-01-20 14:10:10 +0900 | [diff] [blame] | 40 | targets += $(DOCBOOKS) |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 41 | BOOKS := $(addprefix $(obj)/,$(DOCBOOKS)) |
Ben Hutchings | a435600 | 2010-08-10 18:02:51 -0700 | [diff] [blame] | 42 | xmldocs: $(BOOKS) |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 43 | sgmldocs: xmldocs |
| 44 | |
| 45 | PS := $(patsubst %.xml, %.ps, $(BOOKS)) |
| 46 | psdocs: $(PS) |
| 47 | |
| 48 | PDF := $(patsubst %.xml, %.pdf, $(BOOKS)) |
| 49 | pdfdocs: $(PDF) |
| 50 | |
Randy Dunlap | f15a3cc | 2007-04-11 08:44:12 -0700 | [diff] [blame] | 51 | HTML := $(sort $(patsubst %.xml, %.html, $(BOOKS))) |
Mauro Carvalho Chehab | 0489304 | 2011-05-25 12:24:48 -0300 | [diff] [blame] | 52 | htmldocs: $(HTML) |
Mauro Carvalho Chehab | e237b65 | 2015-11-19 12:38:46 -0200 | [diff] [blame] | 53 | $(call cmd,build_main_index) |
Mauro Carvalho Chehab | bd7319d | 2011-06-15 23:13:19 -0300 | [diff] [blame] | 54 | $(call install_media_images) |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 55 | |
| 56 | MAN := $(patsubst %.xml, %.9, $(BOOKS)) |
| 57 | mandocs: $(MAN) |
Ben Hutchings | 32c1735 | 2015-07-08 20:06:44 +0100 | [diff] [blame] | 58 | find $(obj)/man -name '*.9' | xargs gzip -nf |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 59 | |
| 60 | installmandocs: mandocs |
Martin Waitz | 8b0c2d9 | 2005-05-01 08:59:27 -0700 | [diff] [blame] | 61 | mkdir -p /usr/local/man/man9/ |
Ben Hutchings | 9ed71e7 | 2015-08-06 23:36:52 +0100 | [diff] [blame] | 62 | find $(obj)/man -name '*.9.gz' -printf '%h %f\n' | \ |
| 63 | sort -k 2 -k 1 | uniq -f 1 | sed -e 's: :/:' | \ |
| 64 | xargs install -m 644 -t /usr/local/man/man9/ |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 65 | |
| 66 | ### |
| 67 | #External programs used |
Danilo Cesar Lemes de Paula | 5699f87 | 2015-07-28 16:45:15 -0300 | [diff] [blame] | 68 | KERNELDOCXMLREF = $(srctree)/scripts/kernel-doc-xml-ref |
| 69 | KERNELDOC = $(srctree)/scripts/kernel-doc |
| 70 | DOCPROC = $(objtree)/scripts/docproc |
Ben Hutchings | b479bfd | 2015-09-28 01:09:52 +0100 | [diff] [blame] | 71 | CHECK_LC_CTYPE = $(objtree)/scripts/check-lc_ctype |
| 72 | |
| 73 | # Use a fixed encoding - UTF-8 if the C library has support built-in |
| 74 | # or ASCII if not |
| 75 | LC_CTYPE := $(call try-run, LC_CTYPE=C.UTF-8 $(CHECK_LC_CTYPE),C.UTF-8,C) |
| 76 | export LC_CTYPE |
Martin Waitz | 8b0c2d9 | 2005-05-01 08:59:27 -0700 | [diff] [blame] | 77 | |
Masahiro Yamada | ec3fadd | 2014-03-18 15:47:13 +0900 | [diff] [blame] | 78 | XMLTOFLAGS = -m $(srctree)/$(src)/stylesheet.xsl |
Alexey Dobriyan | 82c1e49 | 2009-12-15 16:46:59 -0800 | [diff] [blame] | 79 | XMLTOFLAGS += --skip-validation |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 80 | |
| 81 | ### |
| 82 | # DOCPROC is used for two purposes: |
| 83 | # 1) To generate a dependency list for a .tmpl file |
| 84 | # 2) To preprocess a .tmpl file and call kernel-doc with |
| 85 | # appropriate parameters. |
| 86 | # The following rules are used to generate the .xml documentation |
| 87 | # required to generate the final targets. (ps, pdf, html). |
| 88 | quiet_cmd_docproc = DOCPROC $@ |
| 89 | cmd_docproc = SRCTREE=$(srctree)/ $(DOCPROC) doc $< >$@ |
| 90 | define rule_docproc |
| 91 | set -e; \ |
| 92 | $(if $($(quiet)cmd_$(1)),echo ' $($(quiet)cmd_$(1))';) \ |
| 93 | $(cmd_$(1)); \ |
| 94 | ( \ |
| 95 | echo 'cmd_$@ := $(cmd_$(1))'; \ |
| 96 | echo $@: `SRCTREE=$(srctree) $(DOCPROC) depend $<`; \ |
| 97 | ) > $(dir $@).$(notdir $@).cmd |
| 98 | endef |
| 99 | |
Danilo Cesar Lemes de Paula | 5699f87 | 2015-07-28 16:45:15 -0300 | [diff] [blame] | 100 | %.xml: %.tmpl $(KERNELDOC) $(DOCPROC) $(KERNELDOCXMLREF) FORCE |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 101 | $(call if_changed_rule,docproc) |
| 102 | |
Randy Dunlap | 3794f3e | 2008-08-12 15:09:06 -0700 | [diff] [blame] | 103 | # Tell kbuild to always build the programs |
| 104 | always := $(hostprogs-y) |
| 105 | |
Martin Waitz | 71f95cf | 2005-11-13 16:08:15 -0800 | [diff] [blame] | 106 | notfoundtemplate = echo "*** You have to install docbook-utils or xmlto ***"; \ |
| 107 | exit 1 |
| 108 | db2xtemplate = db2TYPE -o $(dir $@) $< |
| 109 | xmltotemplate = xmlto TYPE $(XMLTOFLAGS) -o $(dir $@) $< |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 110 | |
Martin Waitz | 71f95cf | 2005-11-13 16:08:15 -0800 | [diff] [blame] | 111 | # determine which methods are available |
| 112 | ifeq ($(shell which db2ps >/dev/null 2>&1 && echo found),found) |
| 113 | use-db2x = db2x |
| 114 | prefer-db2x = db2x |
| 115 | else |
| 116 | use-db2x = notfound |
| 117 | prefer-db2x = $(use-xmlto) |
| 118 | endif |
| 119 | ifeq ($(shell which xmlto >/dev/null 2>&1 && echo found),found) |
| 120 | use-xmlto = xmlto |
| 121 | prefer-xmlto = xmlto |
| 122 | else |
| 123 | use-xmlto = notfound |
| 124 | prefer-xmlto = $(use-db2x) |
| 125 | endif |
| 126 | |
| 127 | # the commands, generated from the chosen template |
| 128 | quiet_cmd_db2ps = PS $@ |
| 129 | cmd_db2ps = $(subst TYPE,ps, $($(PS_METHOD)template)) |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 130 | %.ps : %.xml |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 131 | $(call cmd,db2ps) |
| 132 | |
Hans Ulrich Niedermann | a34645f | 2008-10-29 14:00:57 -0700 | [diff] [blame] | 133 | quiet_cmd_db2pdf = PDF $@ |
Martin Waitz | 71f95cf | 2005-11-13 16:08:15 -0800 | [diff] [blame] | 134 | cmd_db2pdf = $(subst TYPE,pdf, $($(PDF_METHOD)template)) |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 135 | %.pdf : %.xml |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 136 | $(call cmd,db2pdf) |
| 137 | |
Borislav Petkov | eb81d93 | 2007-05-08 00:29:36 -0700 | [diff] [blame] | 138 | |
Randy Dunlap | 64e3da1 | 2009-04-17 18:28:55 -0700 | [diff] [blame] | 139 | index = index.html |
Masahiro Yamada | ec3fadd | 2014-03-18 15:47:13 +0900 | [diff] [blame] | 140 | main_idx = $(obj)/$(index) |
Mauro Carvalho Chehab | e237b65 | 2015-11-19 12:38:46 -0200 | [diff] [blame] | 141 | quiet_cmd_build_main_index = HTML $(main_idx) |
| 142 | cmd_build_main_index = rm -rf $(main_idx); \ |
Borislav Petkov | eb81d93 | 2007-05-08 00:29:36 -0700 | [diff] [blame] | 143 | echo '<h1>Linux Kernel HTML Documentation</h1>' >> $(main_idx) && \ |
| 144 | echo '<h2>Kernel Version: $(KERNELVERSION)</h2>' >> $(main_idx) && \ |
| 145 | cat $(HTML) >> $(main_idx) |
| 146 | |
Hans Ulrich Niedermann | a34645f | 2008-10-29 14:00:57 -0700 | [diff] [blame] | 147 | quiet_cmd_db2html = HTML $@ |
Robert P. J. Day | c4d79a4 | 2013-11-06 13:18:27 -0800 | [diff] [blame] | 148 | cmd_db2html = xmlto html $(XMLTOFLAGS) -o $(patsubst %.html,%,$@) $< && \ |
Martin Waitz | 4fa3516 | 2005-05-01 08:59:28 -0700 | [diff] [blame] | 149 | echo '<a HREF="$(patsubst %.html,%,$(notdir $@))/index.html"> \ |
Masahiro Yamada | ec3fadd | 2014-03-18 15:47:13 +0900 | [diff] [blame] | 150 | $(patsubst %.html,%,$(notdir $@))</a><p>' > $@ |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 151 | |
Danilo Cesar Lemes de Paula | 5699f87 | 2015-07-28 16:45:15 -0300 | [diff] [blame] | 152 | ### |
| 153 | # Rules to create an aux XML and .db, and use them to re-process the DocBook XML |
| 154 | # to fill internal hyperlinks |
| 155 | gen_aux_xml = : |
| 156 | quiet_gen_aux_xml = echo ' XMLREF $@' |
| 157 | silent_gen_aux_xml = : |
| 158 | %.aux.xml: %.xml |
| 159 | @$($(quiet)gen_aux_xml) |
| 160 | @rm -rf $@ |
| 161 | @(cat $< | egrep "^<refentry id" | egrep -o "\".*\"" | cut -f 2 -d \" > $<.db) |
| 162 | @$(KERNELDOCXMLREF) -db $<.db $< > $@ |
| 163 | .PRECIOUS: %.aux.xml |
| 164 | |
| 165 | %.html: %.aux.xml |
Martin Waitz | 8b0c2d9 | 2005-05-01 08:59:27 -0700 | [diff] [blame] | 166 | @(which xmlto > /dev/null 2>&1) || \ |
Sam Ravnborg | fd4a324 | 2005-05-01 08:59:28 -0700 | [diff] [blame] | 167 | (echo "*** You need to install xmlto ***"; \ |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 168 | exit 1) |
| 169 | @rm -rf $@ $(patsubst %.html,%,$@) |
| 170 | $(call cmd,db2html) |
| 171 | @if [ ! -z "$(PNG-$(basename $(notdir $@)))" ]; then \ |
| 172 | cp $(PNG-$(basename $(notdir $@))) $(patsubst %.html,%,$@); fi |
| 173 | |
Martin Waitz | 71f95cf | 2005-11-13 16:08:15 -0800 | [diff] [blame] | 174 | quiet_cmd_db2man = MAN $@ |
Ben Hutchings | 9ed71e7 | 2015-08-06 23:36:52 +0100 | [diff] [blame] | 175 | cmd_db2man = if grep -q refentry $<; then xmlto man $(XMLTOFLAGS) -o $(obj)/man/$(*F) $< ; fi |
Martin Waitz | 8b0c2d9 | 2005-05-01 08:59:27 -0700 | [diff] [blame] | 176 | %.9 : %.xml |
| 177 | @(which xmlto > /dev/null 2>&1) || \ |
Sam Ravnborg | fd4a324 | 2005-05-01 08:59:28 -0700 | [diff] [blame] | 178 | (echo "*** You need to install xmlto ***"; \ |
Martin Waitz | 8b0c2d9 | 2005-05-01 08:59:27 -0700 | [diff] [blame] | 179 | exit 1) |
Ben Hutchings | 9ed71e7 | 2015-08-06 23:36:52 +0100 | [diff] [blame] | 180 | $(Q)mkdir -p $(obj)/man/$(*F) |
Martin Waitz | 8b0c2d9 | 2005-05-01 08:59:27 -0700 | [diff] [blame] | 181 | $(call cmd,db2man) |
| 182 | @touch $@ |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 183 | |
| 184 | ### |
Simon Arlott | 0f035b8 | 2007-10-20 01:30:25 +0200 | [diff] [blame] | 185 | # Rules to generate postscripts and PNG images from .fig format files |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 186 | quiet_cmd_fig2eps = FIG2EPS $@ |
| 187 | cmd_fig2eps = fig2dev -Leps $< $@ |
| 188 | |
| 189 | %.eps: %.fig |
| 190 | @(which fig2dev > /dev/null 2>&1) || \ |
| 191 | (echo "*** You need to install transfig ***"; \ |
| 192 | exit 1) |
| 193 | $(call cmd,fig2eps) |
| 194 | |
| 195 | quiet_cmd_fig2png = FIG2PNG $@ |
| 196 | cmd_fig2png = fig2dev -Lpng $< $@ |
| 197 | |
| 198 | %.png: %.fig |
| 199 | @(which fig2dev > /dev/null 2>&1) || \ |
| 200 | (echo "*** You need to install transfig ***"; \ |
| 201 | exit 1) |
| 202 | $(call cmd,fig2png) |
| 203 | |
| 204 | ### |
| 205 | # Rule to convert a .c file to inline XML documentation |
Mike Frysinger | 759cd60 | 2008-03-28 14:30:58 -0700 | [diff] [blame] | 206 | gen_xml = : |
| 207 | quiet_gen_xml = echo ' GEN $@' |
| 208 | silent_gen_xml = : |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 209 | %.xml: %.c |
Mike Frysinger | 759cd60 | 2008-03-28 14:30:58 -0700 | [diff] [blame] | 210 | @$($(quiet)gen_xml) |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 211 | @( \ |
| 212 | echo "<programlisting>"; \ |
| 213 | expand --tabs=8 < $< | \ |
| 214 | sed -e "s/&/\\&/g" \ |
| 215 | -e "s/</\\</g" \ |
| 216 | -e "s/>/\\>/g"; \ |
| 217 | echo "</programlisting>") > $@ |
| 218 | |
| 219 | ### |
| 220 | # Help targets as used by the top-level makefile |
| 221 | dochelp: |
Jesper Juhl | 6fc52f8 | 2006-12-07 00:16:26 +0100 | [diff] [blame] | 222 | @echo ' Linux kernel internal documentation in different formats:' |
| 223 | @echo ' htmldocs - HTML' |
Jesper Juhl | 6fc52f8 | 2006-12-07 00:16:26 +0100 | [diff] [blame] | 224 | @echo ' pdfdocs - PDF' |
| 225 | @echo ' psdocs - Postscript' |
| 226 | @echo ' xmldocs - XML DocBook' |
Randy Dunlap | 2810ae8c | 2009-04-10 14:20:54 -0700 | [diff] [blame] | 227 | @echo ' mandocs - man pages' |
| 228 | @echo ' installmandocs - install man pages generated by mandocs' |
| 229 | @echo ' cleandocs - clean all generated DocBook files' |
Mauro Carvalho Chehab | e57f079 | 2015-11-19 12:38:44 -0200 | [diff] [blame] | 230 | @echo |
| 231 | @echo 'make DOCBOOKS="s1.xml s2.xml" [target] Generate only docs s1.xml s2.xml' |
| 232 | @echo ' valid values for DOCBOOKS are: $(DOCBOOKS)' |
| 233 | |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 234 | |
| 235 | ### |
| 236 | # Temporary files left by various tools |
| 237 | clean-files := $(DOCBOOKS) \ |
Danilo Cesar Lemes de Paula | 5699f87 | 2015-07-28 16:45:15 -0300 | [diff] [blame] | 238 | $(patsubst %.xml, %.dvi, $(DOCBOOKS)) \ |
| 239 | $(patsubst %.xml, %.aux, $(DOCBOOKS)) \ |
| 240 | $(patsubst %.xml, %.tex, $(DOCBOOKS)) \ |
| 241 | $(patsubst %.xml, %.log, $(DOCBOOKS)) \ |
| 242 | $(patsubst %.xml, %.out, $(DOCBOOKS)) \ |
| 243 | $(patsubst %.xml, %.ps, $(DOCBOOKS)) \ |
| 244 | $(patsubst %.xml, %.pdf, $(DOCBOOKS)) \ |
| 245 | $(patsubst %.xml, %.html, $(DOCBOOKS)) \ |
| 246 | $(patsubst %.xml, %.9, $(DOCBOOKS)) \ |
| 247 | $(patsubst %.xml, %.aux.xml, $(DOCBOOKS)) \ |
| 248 | $(patsubst %.xml, %.xml.db, $(DOCBOOKS)) \ |
| 249 | $(patsubst %.xml, %.xml, $(DOCBOOKS)) \ |
Alexey Dobriyan | 82c1e49 | 2009-12-15 16:46:59 -0800 | [diff] [blame] | 250 | $(index) |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 251 | |
Mauro Carvalho Chehab | 4266129 | 2011-05-31 16:27:44 -0300 | [diff] [blame] | 252 | clean-dirs := $(patsubst %.xml,%,$(DOCBOOKS)) man |
Paul Smith | 4f19336 | 2006-03-05 17:14:10 -0500 | [diff] [blame] | 253 | |
Mauro Carvalho Chehab | 4266129 | 2011-05-31 16:27:44 -0300 | [diff] [blame] | 254 | cleandocs: cleanmediadocs |
Randy Dunlap | 2810ae8c | 2009-04-10 14:20:54 -0700 | [diff] [blame] | 255 | $(Q)rm -f $(call objectify, $(clean-files)) |
| 256 | $(Q)rm -rf $(call objectify, $(clean-dirs)) |
| 257 | |
Paul Smith | 4f19336 | 2006-03-05 17:14:10 -0500 | [diff] [blame] | 258 | # Declare the contents of the .PHONY variable as phony. We keep that |
| 259 | # information in a variable se we can use it in if_changed and friends. |
| 260 | |
| 261 | .PHONY: $(PHONY) |