diff options
author | Mauro Carvalho Chehab <mchehab@s-opensource.com> | 2017-04-05 09:23:09 -0400 |
---|---|---|
committer | Jonathan Corbet <corbet@lwn.net> | 2017-04-11 16:40:12 -0400 |
commit | 32a3bebce9d09598d4f4c5afca929a2ce148b8c4 (patch) | |
tree | a0ac3c5bddc53cc9a21575274a9711a29b4af796 | |
parent | 76f650f077f3edd7001c89da44eade2449e8f495 (diff) |
usb/persist.txt: convert to ReST and add to driver-api book
This document describe some USB core features. Add it to the
driver-api book.
Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>
Acked-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>
-rw-r--r-- | Documentation/driver-api/usb/index.rst | 1 | ||||
-rw-r--r-- | Documentation/driver-api/usb/persist.rst (renamed from Documentation/usb/persist.txt) | 22 |
2 files changed, 14 insertions, 9 deletions
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 | |||
12 | dma | 12 | dma |
13 | power-management | 13 | power-management |
14 | hotplug | 14 | hotplug |
15 | persist | ||
15 | error-codes | 16 | error-codes |
16 | writing_usb_driver | 17 | writing_usb_driver |
17 | writing_musb_glue_layer | 18 | writing_musb_glue_layer |
diff --git a/Documentation/usb/persist.txt b/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 @@ | |||
1 | USB device persistence during system suspend | 1 | USB device persistence during system suspend |
2 | ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ | ||
2 | 3 | ||
3 | Alan Stern <stern@rowland.harvard.edu> | 4 | :Author: Alan Stern <stern@rowland.harvard.edu> |
5 | :Date: September 2, 2006 (Updated February 25, 2008) | ||
4 | 6 | ||
5 | September 2, 2006 (Updated February 25, 2008) | ||
6 | 7 | ||
7 | 8 | What is the problem? | |
8 | What is the problem? | 9 | ==================== |
9 | 10 | ||
10 | According to the USB specification, when a USB bus is suspended the | 11 | According to the USB specification, when a USB bus is suspended the |
11 | bus must continue to supply suspend current (around 1-5 mA). This | 12 | 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 | |||
63 | much better.) | 64 | much better.) |
64 | 65 | ||
65 | 66 | ||
66 | What is the solution? | 67 | What is the solution? |
68 | ===================== | ||
67 | 69 | ||
68 | The kernel includes a feature called USB-persist. It tries to work | 70 | The kernel includes a feature called USB-persist. It tries to work |
69 | around these issues by allowing the core USB device data structures to | 71 | around these issues by allowing the core USB device data structures to |
@@ -99,7 +101,7 @@ now a good and happy place. | |||
99 | 101 | ||
100 | Note that the "USB-persist" feature will be applied only to those | 102 | Note that the "USB-persist" feature will be applied only to those |
101 | devices for which it is enabled. You can enable the feature by doing | 103 | devices for which it is enabled. You can enable the feature by doing |
102 | (as root): | 104 | (as root):: |
103 | 105 | ||
104 | echo 1 >/sys/bus/usb/devices/.../power/persist | 106 | echo 1 >/sys/bus/usb/devices/.../power/persist |
105 | 107 | ||
@@ -110,7 +112,8 @@ doesn't even exist, so you only have to worry about setting it for | |||
110 | devices where it really matters. | 112 | devices where it really matters. |
111 | 113 | ||
112 | 114 | ||
113 | Is this the best solution? | 115 | Is this the best solution? |
116 | ========================== | ||
114 | 117 | ||
115 | Perhaps not. Arguably, keeping track of mounted filesystems and | 118 | Perhaps not. Arguably, keeping track of mounted filesystems and |
116 | memory mappings across device disconnects should be handled by a | 119 | 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 | |||
130 | other device types, such as network interfaces. | 133 | other device types, such as network interfaces. |
131 | 134 | ||
132 | 135 | ||
133 | WARNING: USB-persist can be dangerous!! | 136 | WARNING: USB-persist can be dangerous!! |
137 | ======================================= | ||
134 | 138 | ||
135 | When recovering an interrupted power session the kernel does its best | 139 | When recovering an interrupted power session the kernel does its best |
136 | to make sure the USB device hasn't been changed; that is, the same | 140 | to make sure the USB device hasn't been changed; that is, the same |