Enable/disable CONFIG_USB_SUSPEND's autosuspend mode
 

(from the original barry-devel email posting by Chris Frey, barry author)
http://sourceforge.net/mailarchive/f...me=barry-devel

Kernels:
========

Version 2.6.21 behaves with autosuspend=0 meaning off, while 2.6.22 and higher needs autosuspend=-1 to turn it off. In 2.6.22, a value of 0 means "immediate" instead of "never".

Version 2.6.22 adds variables internal to the system called autosuspend_disabled and autoresume_disabled. These are controlled by the /sys/class/usb_device/*/device/power/level file. (See below)

Here's a summary of files under device/power. These may or may not exist on your system depending on your kernel version and configuration.

autosuspend

-1 or 0 means off, depending on kernel, otherwise it is the number of seconds to autosuspend level with the settings:

on - suspend is disabled, device is fully powered
auto - suspend is controlled by the kernel (default)
suspend - suspend is enabled permanently

You can write these strings to the file to control behaviour on a per-device basis.

echo on > /sys/usb_device/.../device/power/level

state

current state of device
0 - fully powered
2 - suspended

You can write these numbers to control behaviour, but any change you make here might change automatically if autosuspend is on.

echo -n 0 > /sys/usb_device/.../device/power/state

wakeup

unknown

Based on the feedback from Chuck Ebbert, it is possible to disable autosuspend on a system wide basis as well. This is either done on the kernel boot command line if usbcore is compiled into the kernel, or on the module command line, if not.

Here are some practical notes for various distros:


Debian / Ubuntu systems:
========================

Comes with usbcore (CONFIG_USB) compiled as a module and CONFIG_USB_SUSPEND enabled (at least on Ubuntu).

Therefore, to disable autosuspend you either:

- recompile kernel without CONFIG_USB_SUSPEND

- configure /etc/modprobe.d/ with a file containing

"options usbcore autosuspend=-1"
or set to 0 depending on your kernel

If your system needs the modprobe configuration file above, and if your
system uses initrd (probably does) then you will need to rebuild the
initrd for your kernel for this to take effect. For example:

dpkg-reconfigure linux-image-2.6.22.1

Fedora 6 and 7 systems:
=======================

Comes with usbcore (CONFIG_USB) compiled into the the kernel, and CONFIG_USB_SUSPEND enabled on Fedora 7.

Therefore to disable autosuspend you either:

- recompile kernel without CONFIG_USB_SUSPEND

- boot with one of the following, depending on your kernel version (2.6.21 or 2.6.22 respectively):

usbcore.autosuspend=0
usbcore.autosuspend=-1

Summary:
========

It seems that bcharge could be coded to search for device/power/level, device/power/autosuspend, and device/power/state and use some heuristics to decide what best action to take.

Fortunately, the kernel gives an error if you write -1 to autosuspend and the kernel doesn't support it, in which case writing 0 seems to be the next step. :-)

Unfortunately, the files under device/power do not always exist, even while autosuspend is enabled, from what I can tell. I'll update bcharge soon to try to handle this automatically, but I'm not sure it will work in every case.

Rivviepop,

What about the usb suspend workaround patch? I've patched my 2.6.22.9 kernel with that patch and it still works fine. Basically, it tells the usb port not to autospend when blackberry devices are connected.

As far as I know, this is pretty much the laziest, no brainer way to get the bb's charged at the correct amp, no messing with the kernel or module lines and no scripts needed either. Who wouldn't want that? (y)

Check out the brand new barry 0.9 released, it's supposed to fix the issue with kernels that have it enabled using some voodoo, sleight of hand and a few magic tricks. :) I'll post a thread in a sec with the release announcement and changelog.