docs: Move rustdoc output, cross-reference it

Generate rustdoc documentation with the rest of subsystem's documentation
in Documentation/output. Add a cross reference to the generated rustdoc in
Documentation/rust/index.rst if Sphinx target rustdoc is set.
Reviewed-by: Akira Yokosawa <akiyks@gmail.com>
Signed-off-by: Carlos Bilbao <carlos.bilbao@amd.com>
Reviewed-by: Martin Rodriguez Reboredo <yakoyoku@gmail.com>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>
Link: https://lore.kernel.org/r/20230718151534.4067460-2-carlos.bilbao@amd.com

Documentation/rust/index.rst

@@ -6,6 +6,14 @@ Rust
 Documentation related to Rust within the kernel. To start using Rust
 in the kernel, please read the quick-start.rst guide.
 
+.. only:: rustdoc and html
+
+	You can also browse `rustdoc documentation <rustdoc/kernel/index.html>`_.
+
+.. only:: not rustdoc and html
+
+	This documentation does not include rustdoc generated information.
+
 .. toctree::
     :maxdepth: 1
 

rust/Makefile

 # SPDX-License-Identifier: GPL-2.0
 
+# Where to place rustdoc generated documentation
+rustdoc_output := $(objtree)/Documentation/output/rust/rustdoc
+
 obj-$(CONFIG_RUST) += core.o compiler_builtins.o
 always-$(CONFIG_RUST) += exports_core_generated.h
 
@@ -65,7 +68,7 @@ quiet_cmd_rustdoc = RUSTDOC $(if $(rustdoc_host),H, ) $<
 	OBJTREE=$(abspath $(objtree)) \
 	$(RUSTDOC) $(if $(rustdoc_host),$(rust_common_flags),$(rust_flags)) \
 		$(rustc_target_flags) -L$(objtree)/$(obj) \
-		--output $(objtree)/$(obj)/doc \
+		--output $(rustdoc_output) \
 		--crate-name $(subst rustdoc-,,$@) \
 		@$(objtree)/include/generated/rustc_cfg $<
 
@@ -82,15 +85,15 @@ quiet_cmd_rustdoc = RUSTDOC $(if $(rustdoc_host),H, ) $<
 # and then retouch the generated files.
 rustdoc: rustdoc-core rustdoc-macros rustdoc-compiler_builtins \
     rustdoc-alloc rustdoc-kernel
-	$(Q)cp $(srctree)/Documentation/images/logo.svg $(objtree)/$(obj)/doc
-	$(Q)cp $(srctree)/Documentation/images/COPYING-logo $(objtree)/$(obj)/doc
-	$(Q)find $(objtree)/$(obj)/doc -name '*.html' -type f -print0 | xargs -0 sed -Ei \
+	$(Q)cp $(srctree)/Documentation/images/logo.svg $(rustdoc_output)
+	$(Q)cp $(srctree)/Documentation/images/COPYING-logo $(rustdoc_output)
+	$(Q)find $(rustdoc_output) -name '*.html' -type f -print0 | xargs -0 sed -Ei \
 		-e 's:rust-logo\.svg:logo.svg:g' \
 		-e 's:rust-logo\.png:logo.svg:g' \
 		-e 's:favicon\.svg:logo.svg:g' \
 		-e 's:<link rel="alternate icon" type="image/png" href="[./]*favicon-(16x16|32x32)\.png">::g'
 	$(Q)echo '.logo-container > img { object-fit: contain; }' \
-		>> $(objtree)/$(obj)/doc/rustdoc.css
+		>> $(rustdoc_output)/rustdoc.css
 
 rustdoc-macros: private rustdoc_host = yes
 rustdoc-macros: private rustc_target_flags = --crate-type proc-macro \
@@ -154,7 +157,7 @@ quiet_cmd_rustdoc_test = RUSTDOC T $<
 		@$(objtree)/include/generated/rustc_cfg \
 		$(rustc_target_flags) $(rustdoc_test_target_flags) \
 		--sysroot $(objtree)/$(obj)/test/sysroot $(rustdoc_test_quiet) \
-		-L$(objtree)/$(obj)/test --output $(objtree)/$(obj)/doc \
+		-L$(objtree)/$(obj)/test --output $(rustdoc_output) \
 		--crate-name $(subst rusttest-,,$@) $<
 
 # We cannot use `-Zpanic-abort-tests` because some tests are dynamic,