Merge branches 'fixes' and 'misc' into for-linus

[linux.git] / Documentation / io-mapping.txt

diff --git a/Documentation/io-mapping.txt b/Documentation/io-mapping.txt
index 5ca78426f54c58d10e3fd0030ad51f6ccb2b5b9b..a966239f04e489c58d2fc07f9f10922cf7f2010b 100644 (file)
--- a/Documentation/io-mapping.txt
+++ b/Documentation/io-mapping.txt
@@ -1,66 +1,81 @@
+========================
+The io_mapping functions
+========================
+
+API
+===
+

 The io_mapping functions in linux/io-mapping.h provide an abstraction for
 efficiently mapping small regions of an I/O device to the CPU. The initial
 usage is to support the large graphics aperture on 32-bit processors where
 ioremap_wc cannot be used to statically map the entire aperture to the CPU
 as it would consume too much of the kernel address space.
 
 The io_mapping functions in linux/io-mapping.h provide an abstraction for
 efficiently mapping small regions of an I/O device to the CPU. The initial
 usage is to support the large graphics aperture on 32-bit processors where
 ioremap_wc cannot be used to statically map the entire aperture to the CPU
 as it would consume too much of the kernel address space.
 

-A mapping object is created during driver initialization using
+A mapping object is created during driver initialization using::

 
        struct io_mapping *io_mapping_create_wc(unsigned long base,
                                                unsigned long size)
 
 
        struct io_mapping *io_mapping_create_wc(unsigned long base,
                                                unsigned long size)
 

-               'base' is the bus address of the region to be made
-               mappable, while 'size' indicates how large a mapping region to
-               enable. Both are in bytes.
+'base' is the bus address of the region to be made
+mappable, while 'size' indicates how large a mapping region to
+enable. Both are in bytes.

 
 

-               This _wc variant provides a mapping which may only be used
-               with the io_mapping_map_atomic_wc or io_mapping_map_wc.
+This _wc variant provides a mapping which may only be used
+with the io_mapping_map_atomic_wc or io_mapping_map_wc.

 
 With this mapping object, individual pages can be mapped either atomically
 or not, depending on the necessary scheduling environment. Of course, atomic
 
 With this mapping object, individual pages can be mapped either atomically
 or not, depending on the necessary scheduling environment. Of course, atomic

-maps are more efficient:
+maps are more efficient::

 
        void *io_mapping_map_atomic_wc(struct io_mapping *mapping,
                                       unsigned long offset)
 
 
        void *io_mapping_map_atomic_wc(struct io_mapping *mapping,
                                       unsigned long offset)
 

-               'offset' is the offset within the defined mapping region.
-               Accessing addresses beyond the region specified in the
-               creation function yields undefined results. Using an offset
-               which is not page aligned yields an undefined result. The
-               return value points to a single page in CPU address space.
+'offset' is the offset within the defined mapping region.
+Accessing addresses beyond the region specified in the
+creation function yields undefined results. Using an offset
+which is not page aligned yields an undefined result. The
+return value points to a single page in CPU address space.
+
+This _wc variant returns a write-combining map to the
+page and may only be used with mappings created by
+io_mapping_create_wc

 
 

-               This _wc variant returns a write-combining map to the
-               page and may only be used with mappings created by
-               io_mapping_create_wc
+Note that the task may not sleep while holding this page
+mapped.

 
 

-               Note that the task may not sleep while holding this page
-               mapped.
+::

 
        void io_mapping_unmap_atomic(void *vaddr)
 
 
        void io_mapping_unmap_atomic(void *vaddr)
 

-               'vaddr' must be the value returned by the last
-               io_mapping_map_atomic_wc call. This unmaps the specified
-               page and allows the task to sleep once again.
+'vaddr' must be the value returned by the last
+io_mapping_map_atomic_wc call. This unmaps the specified
+page and allows the task to sleep once again.

 
 If you need to sleep while holding the lock, you can use the non-atomic
 variant, although they may be significantly slower.
 
 
 If you need to sleep while holding the lock, you can use the non-atomic
 variant, although they may be significantly slower.
 

+::
+

        void *io_mapping_map_wc(struct io_mapping *mapping,
                                unsigned long offset)
 
        void *io_mapping_map_wc(struct io_mapping *mapping,
                                unsigned long offset)
 

-               This works like io_mapping_map_atomic_wc except it allows
-               the task to sleep while holding the page mapped.
+This works like io_mapping_map_atomic_wc except it allows
+the task to sleep while holding the page mapped.
+
+
+::

 
        void io_mapping_unmap(void *vaddr)
 
 
        void io_mapping_unmap(void *vaddr)
 

-               This works like io_mapping_unmap_atomic, except it is used
-               for pages mapped with io_mapping_map_wc.
+This works like io_mapping_unmap_atomic, except it is used
+for pages mapped with io_mapping_map_wc.

 
 

-At driver close time, the io_mapping object must be freed:
+At driver close time, the io_mapping object must be freed::

 
        void io_mapping_free(struct io_mapping *mapping)
 
 
        void io_mapping_free(struct io_mapping *mapping)
 

-Current Implementation:
+Current Implementation
+======================

 
 The initial implementation of these functions uses existing mapping
 mechanisms and so provides only an abstraction layer and no new
 
 The initial implementation of these functions uses existing mapping
 mechanisms and so provides only an abstraction layer and no new