This document describe some USB core features. Add it to the
driver-api book.
Signed-off-by: Mauro Carvalho Chehab <mche...@s-opensource.com>
---
Documentation/driver-api/usb/index.rst | 1 +
.../persist.txt => driver-api/usb/persist.rst} | 22 +++++++++++++---------
2 files changed, 14 insertions(+), 9 deletions(-)
rename Documentation/{usb/persist.txt => driver-api/usb/persist.rst} (94%)
diff --git a/Documentation/driver-api/usb/index.rst
b/Documentation/driver-api/usb/index.rst
index 43f0a8b72b11..3f08cb5d5feb 100644
--- a/Documentation/driver-api/usb/index.rst
+++ b/Documentation/driver-api/usb/index.rst
@@ -12,6 +12,7 @@ Linux USB API
dma
power-management
hotplug
+ persist
error-codes
writing_usb_driver
writing_musb_glue_layer
diff --git a/Documentation/usb/persist.txt
b/Documentation/driver-api/usb/persist.rst
similarity index 94%
rename from Documentation/usb/persist.txt
rename to Documentation/driver-api/usb/persist.rst
index 35d70eda9ad6..ea1b43f0559e 100644
--- a/Documentation/usb/persist.txt
+++ b/Documentation/driver-api/usb/persist.rst
@@ -1,11 +1,12 @@
- USB device persistence during system suspend
+USB device persistence during system suspend
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
- Alan Stern <st...@rowland.harvard.edu>
+:Author: Alan Stern <st...@rowland.harvard.edu>
+:Date: September 2, 2006 (Updated February 25, 2008)
- September 2, 2006 (Updated February 25, 2008)
-
- What is the problem?
+What is the problem?
+====================
According to the USB specification, when a USB bus is suspended the
bus must continue to supply suspend current (around 1-5 mA). This
@@ -63,7 +64,8 @@ suspended -- but it will crash as soon as it wakes up, which
isn't
much better.)
- What is the solution?
+What is the solution?
+=====================
The kernel includes a feature called USB-persist. It tries to work
around these issues by allowing the core USB device data structures to
@@ -99,7 +101,7 @@ now a good and happy place.
Note that the "USB-persist" feature will be applied only to those
devices for which it is enabled. You can enable the feature by doing
-(as root):
+(as root)::
echo 1 >/sys/bus/usb/devices/.../power/persist
@@ -110,7 +112,8 @@ doesn't even exist, so you only have to worry about setting
it for
devices where it really matters.
- Is this the best solution?
+Is this the best solution?
+==========================
Perhaps not. Arguably, keeping track of mounted filesystems and
memory mappings across device disconnects should be handled by a
@@ -130,7 +133,8 @@ just mass-storage devices. It might turn out to be equally
useful for
other device types, such as network interfaces.
- WARNING: USB-persist can be dangerous!!
+WARNING: USB-persist can be dangerous!!
+=======================================
When recovering an interrupted power session the kernel does its best
to make sure the USB device hasn't been changed; that is, the same
--
2.9.3
