firmware: Add CONFIG_EXTRA_FIRMWARE option

This allows arbitrary firmware files to be included in the static kernel
where the firmware loader can find them without requiring userspace to
be alive.

(Updated and CONFIG_EXTRA_FIRMWARE_DIR added with lots of help from
Johannes Berg).

Signed-off-by: David Woodhouse <dwmw2@infradead.org>
Signed-off-by: Johannes Berg <johannes@sipsolutions.net>

3 files changed, 128 insertions, 1 deletions

diff --git a/Makefile b/Makefile
index 6315424a00b9..f398cffa6c07 100644
--- a/Makefile
+++ b/Makefile
@@ -450,7 +450,7 @@ scripts: scripts_basic include/config/auto.conf
 
 # Objects we will link into vmlinux / subdirs we need to visit
 init-y          := init/
-drivers-y       := drivers/ sound/
+drivers-y       := drivers/ sound/ firmware/
 net-y           := net/
 libs-y          := lib/
 core-y          := usr/
diff --git a/drivers/base/Kconfig b/drivers/base/Kconfig
index d7da109c24fd..13cfcb435f7d 100644
--- a/drivers/base/Kconfig
+++ b/drivers/base/Kconfig
@@ -34,6 +34,45 @@ config FW_LOADER
           require userspace firmware loading support, but a module built outside
           the kernel tree does.
 
+config EXTRA_FIRMWARE
+        string "External firmware blobs to build into the kernel binary"
+        depends on FW_LOADER
+        help
+          This option allows firmware to be built into the kernel, for the
+          cases where the user either cannot or doesn't want to provide it from
+          userspace at runtime (for example, when the firmware in question is
+          required for accessing the boot device, and the user doesn't want to
+          use an initrd).
+
+          This option is a string, and takes the (space-separated) names of the
+          firmware files -- the same names which appear in MODULE_FIRMWARE()
+          and request_firmware() in the source. These files should exist under
+          the directory specified by the EXTRA_FIRMWARE_DIR option, which is
+          by default the firmware/ subdirectory of the kernel source tree.
+
+          So, for example, you might set CONFIG_EXTRA_FIRMWARE="usb8388.bin",
+          copy the usb8388.bin file into the firmware/ directory, and build the
+          kernel. Then any request_firmware("usb8388.bin") will be
+          satisfied internally without needing to call out to userspace.
+
+          WARNING: If you include additional firmware files into your binary
+          kernel image which are not available under the terms of the GPL,
+          then it may be a violation of the GPL to distribute the resulting
+          image -- since it combines both GPL and non-GPL work. You should
+          consult a lawyer of your own before distributing such an image.
+
+config EXTRA_FIRMWARE_DIR
+        string "Firmware blobs root directory"
+        depends on EXTRA_FIRMWARE != ""
+        default "firmware"
+        help
+          This option controls the directory in which the kernel build system
+          looks for the firmware files listed in the EXTRA_FIRMWARE option.
+          The default is the firmware/ directory in the kernel source tree,
+          but by changing this option you can point it elsewhere, such as
+          the /lib/firmware/ directory or another separate directory
+          containing firmware files.
+
 config DEBUG_DRIVER
         bool "Driver Core verbose debug messages"
         depends on DEBUG_KERNEL
diff --git a/firmware/Makefile b/firmware/Makefile
new file mode 100644
index 000000000000..e69461f9362b
--- /dev/null
+++ b/firmware/Makefile
@@ -0,0 +1,88 @@
+#
+# kbuild file for firmware/
+#
+
+# Create $(fwabs) from $(CONFIG_EXTRA_FIRMWARE_DIR) -- if it doesn't have a
+# leading /, it's relative to $(srctree).
+fwdir := $(subst ",,$(CONFIG_EXTRA_FIRMWARE_DIR))
+fwabs := $(addprefix $(srctree)/,$(filter-out /%,$(fwdir)))$(filter /%,$(fwdir))
+
+fw-external-y := $(subst ",,$(CONFIG_EXTRA_FIRMWARE))
+
+firmware-y    := $(fw-external-y) $(fw-shipped-y)
+firmware-dirs := $(sort $(patsubst %,$(objtree)/$(obj)/%/,$(dir $(firmware-y) $(fw-shipped-))))
+
+quiet_cmd_mkdir = MKDIR   $(patsubst $(objtree)/%,%,$@)
+      cmd_mkdir = mkdir -p $@
+
+quiet_cmd_ihex  = IHEX    $@
+      cmd_ihex  = $(OBJCOPY) -Iihex -Obinary $< $@
+
+quiet_cmd_fwbin = MK_FW   $@
+      cmd_fwbin = FWNAME="$(patsubst firmware/%.gen.S,%,$@)";                \
+                  FWSTR="$(subst /,_,$(subst .,_,$(subst -,_,$(patsubst      \
+                                firmware/%.gen.S,%,$@))))";                  \
+                  ASM_WORD=$(if $(CONFIG_64BIT),.quad,.long);                \
+                  ASM_ALIGN=$(if $(CONFIG_64BIT),3,2);                       \
+                  PROGBITS=$(if $(CONFIG_ARM),%,@)progbits;                  \
+                  echo "/* Generated by firmware/Makefile */"           > $@;\
+                  echo "    .section .rodata"                           >>$@;\
+                  echo "    .p2align $${ASM_ALIGN}"                     >>$@;\
+                  echo "_fw_$${FWSTR}_bin:"                             >>$@;\
+                  echo "    .incbin \"$(2)\""                           >>$@;\
+                  echo "_fw_end:"                                       >>$@;\
+                  echo "   .section .rodata.str,\"aMS\",$${PROGBITS},1" >>$@;\
+                  echo "    .p2align $${ASM_ALIGN}"                     >>$@;\
+                  echo "_fw_$${FWSTR}_name:"                            >>$@;\
+                  echo "    .string \"$$FWNAME\""                       >>$@;\
+                  echo "    .section .builtin_fw,\"a\",$${PROGBITS}"    >>$@;\
+                  echo "    .p2align $${ASM_ALIGN}"                     >>$@;\
+                  echo "    $${ASM_WORD} _fw_$${FWSTR}_name"            >>$@;\
+                  echo "    $${ASM_WORD} _fw_$${FWSTR}_bin"             >>$@;\
+                  echo "    $${ASM_WORD} _fw_end - _fw_$${FWSTR}_bin"   >>$@;
+
+# One of these files will change, or come into existence, whenever
+# the configuration changes between 32-bit and 64-bit. The .S files
+# need to change when that happens.
+wordsize_deps := $(wildcard include/config/64bit.h include/config/32bit.h \
+                include/config/ppc32.h include/config/ppc64.h \
+                include/config/superh32.h include/config/superh64.h \
+                include/config/x86_32.h include/config/x86_64.h)
+
+# Workaround for make < 3.81, where .SECONDEXPANSION doesn't work.
+# It'll end up depending on these targets, so make them a PHONY rule which
+# depends on _all_ the directories in $(firmware-dirs), and it'll work out OK.
+PHONY += $(objtree)/$$(%) $(objtree)/$(obj)/$$(%)
+$(objtree)/$$(%) $(objtree)/$(obj)/$$(%): $(firmware-dirs)
+        @true
+
+# For the $$(dir %) trick, where we need % to be expanded first.
+.SECONDEXPANSION:
+
+$(patsubst %,$(obj)/%.gen.S, $(fw-shipped-y)): %: $(wordsize_deps) \
+                | $(objtree)/$$(dir %)
+        $(call cmd,fwbin,$(patsubst %.gen.S,%,$@))
+$(patsubst %,$(obj)/%.gen.S, $(fw-external-y)): %: $(wordsize_deps) \
+                include/config/builtin/firmware/dir.h | $(objtree)/$$(dir %)
+        $(call cmd,fwbin,$(fwabs)/$(patsubst $(obj)/%.gen.S,%,$@))
+
+# The .o files depend on the binaries directly; the .S files don't.
+$(patsubst %,$(obj)/%.gen.o, $(fw-shipped-y)): %.gen.o: %
+$(patsubst %,$(obj)/%.gen.o, $(fw-external-y)): $(obj)/%.gen.o: $(fwdir)/%
+
+$(obj)/%: $(obj)/%.ihex | $(objtree)/$(obj)/$$(dir %)
+        $(call cmd,ihex)
+
+$(firmware-dirs):
+        $(call cmd,mkdir)
+
+obj-y := $(patsubst %,%.gen.o, $(firmware-y))
+
+# Remove .S files and binaries created from ihex
+# (during 'make clean' .config isn't included so they're all in $(fw-shipped-))
+targets := $(fw-shipped-) $(patsubst $(obj)/%,%, \
+                                $(shell find $(obj) -name \*.gen.S 2>/dev/null))
+
+# Without this, built-in.o won't be created when it's empty, and the
+# final vmlinux link will fail.
+obj-n := dummy