p71924506
/
linux_old1
1
0
Fork 0
Code Issues Pull Requests Projects Releases Wiki Activity

io-mapping.txt: standardize document format 

Each text file under Documentation follows a different
format. Some doesn't even have titles!

Change its representation to follow the adopted standard,
using ReST markups for it to be parseable by Sphinx:

- Add a title for the document and for API chapter;
- mark literal blocks;
- Adjust whitespacing.

Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>
This commit is contained in:
Mauro Carvalho Chehab 2017-05-14 14:32:35 -03:00 committed by Jonathan Corbet
parent 45d8514626
commit 9cf5116d5b
1 changed files with 41 additions and 26 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

23
Documentation/io-mapping.txt
View File

@ -1,10 +1,17 @@
========================
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.
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)
@ -18,7 +25,7 @@ A mapping object is created during driver initialization using
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)
@ -36,6 +43,8 @@ maps are more efficient:
Note that the task may not sleep while holding this page
mapped.
::
void io_mapping_unmap_atomic(void *vaddr)
'vaddr' must be the value returned by the last
@ -45,22 +54,28 @@ maps are more efficient:
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)
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)
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)
Current Implementation:
Current Implementation
======================
The initial implementation of these functions uses existing mapping
mechanisms and so provides only an abstraction layer and no new