[PATCH] mm/doc: Include highmem.h in kernel-doc

[PATCH] mm/doc: Include highmem.h in kernel-doc

[Matthew Wilcox (Oracle)]

There is lots of good documentation in highmem.h that isn't being pulled
into the html documentation.  Fix up a couple of minor glitches and
include it.

Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
---
 Documentation/core-api/mm-api.rst |  1 +
 include/linux/highmem.h           | 17 +++++++++--------
 2 files changed, 10 insertions(+), 8 deletions(-)

diff --git a/Documentation/core-api/mm-api.rst b/Documentation/core-api/mm-api.rst
index 395835f9289f..2027aee5f2d9 100644
--- a/Documentation/core-api/mm-api.rst
+++ b/Documentation/core-api/mm-api.rst
@@ -54,6 +54,7 @@ Virtually Contiguous Mappings
 
 .. kernel-doc:: mm/vmalloc.c
    :export:
+.. kernel-doc:: include/linux/highmem.h
 
 File Mapping and Page Cache
 ===========================
diff --git a/include/linux/highmem.h b/include/linux/highmem.h
index 861ad00fb32a..fc43e81cf4db 100644
--- a/include/linux/highmem.h
+++ b/include/linux/highmem.h
@@ -37,8 +37,8 @@
 static inline void *kmap(struct page *page);
 
 /**
- * kunmap - Unmap the virtual address mapped by kmap()
- * @addr:	Virtual address to be unmapped
+ * kunmap - Unmap the page mapped by kmap()
+ * @page: Page to be unmapped
  *
  * Counterpart to kmap(). A NOOP for CONFIG_HIGHMEM=n and for mappings of
  * pages in the low memory area.
@@ -69,13 +69,13 @@ static inline void kmap_flush_unused(void);
  *
  * Requires careful handling when nesting multiple mappings because the map
  * management is stack based. The unmap has to be in the reverse order of
- * the map operation:
+ * the map operation::
  *
- * addr1 = kmap_local_page(page1);
- * addr2 = kmap_local_page(page2);
- * ...
- * kunmap_local(addr2);
- * kunmap_local(addr1);
+ *   addr1 = kmap_local_page(page1);
+ *   addr2 = kmap_local_page(page2);
+ *   ...
+ *   kunmap_local(addr2);
+ *   kunmap_local(addr1);
  *
  * Unmapping addr1 before addr2 is invalid and causes malfunction.
  *
@@ -156,6 +156,7 @@ static inline void *kmap_atomic(struct page *page);
  * the side effects of kmap_atomic(), i.e. reenabling pagefaults and
  * preemption.
  */
+static inline void kunmap_atomic(void *addr);
 
 /* Highmem related interfaces for management code */
 static inline unsigned int nr_free_highpages(void);
-- 
2.30.2

Re: [PATCH] mm/doc: Include highmem.h in kernel-doc

[Andrew Morton]

On Thu, 22 Jul 2021 03:18:42 +0100 "Matthew Wilcox (Oracle)" <willy@infradead.org> wrote:

> There is lots of good documentation in highmem.h that isn't being pulled
> into the html documentation.  Fix up a couple of minor glitches and
> include it.
> 
> --- a/include/linux/highmem.h
> +++ b/include/linux/highmem.h
>
> ...
>
> @@ -156,6 +156,7 @@ static inline void *kmap_atomic(struct page *page);
>   * the side effects of kmap_atomic(), i.e. reenabling pagefaults and
>   * preemption.
>   */
> +static inline void kunmap_atomic(void *addr);
>  
>  /* Highmem related interfaces for management code */
>  static inline unsigned int nr_free_highpages(void);

This hunk broke the i386 allmodconfig build.


In file included from ./include/linux/highmem.h:14,
                 from ./include/linux/bio.h:8,
                 from ./include/linux/blkdev.h:18,
                 from ./include/linux/blk-cgroup.h:23,
                 from ./include/linux/writeback.h:14,
                 from ./include/linux/memcontrol.h:22,
                 from ./include/linux/swap.h:9,
                 from ./include/linux/suspend.h:5,
                 from arch/x86/kernel/asm-offsets.c:13:
./include/linux/highmem-internal.h:216:1: error: expected identifier or '(' before 'do'
  216 | do {        \
      | ^~
./include/linux/highmem.h:122:20: note: in expansion of macro 'kunmap_atomic'
  122 | static inline void kunmap_atomic(void *addr);
      |                    ^~~~~~~~~~~~~
./include/linux/highmem-internal.h:219:3: error: expected identifier or '(' before 'while'
  219 | } while (0)
      |   ^~~~~
./include/linux/highmem.h:122:20: note: in expansion of macro 'kunmap_atomic'
  122 | static inline void kunmap_atomic(void *addr);
      |                    ^~~~~~~~~~~~~
make[1]: *** [scripts/Makefile.build:117: arch/x86/kernel/asm-offsets.s] Error 1
make: *** [Makefile:1213: prepare0] Error 2

I think I can see what you were trying to do there.  How about we
instead move the kunmap_atomic() kerneldoc to an appropriate place?