On Wed, 31 Jan 2007, Oliver Neukum wrote:
> This would call mod_timer() for every completed in-URB. Are you
> sure this is better than an approach maintaining a periodical timer
> and check for IO in the meantime?
I think we can have it both ways. Add an atomic bitflag to the usb_device
structure and have the autosuspend work routine check whether the flag is
set. If it is, just restart the timer. The HID driver can simply set the
flag whenever an URB is received.
There are other changes we should make that would go along with this.
The existing bitfields in usb_device should be changed over
to atomic bitflags, to make them SMP-safe.
The default autosuspend delay should become a usbcore module
parameter rather than a constant. 0 can mean "don't autosuspend".
Your new autosuspend attribute file should be renamed to
autosuspend_delay and it should expose an unsigned short instead
of a boolean: the number of seconds for the device's autosuspend
timer. 0 can mean "don't autosuspend".
We should add a similar "suspend" attribute file. Writing
"1" would immediately suspend and "0" would immediately resume
the device. This will allow userspace to micro-manage the
device state and will replace the deprecated power/state file.
We should write sysfs_add_to_group(), so that these two
attributes can be added to the existing device/power
subdirectory. (sysfs_remove_from_group() doesn't seem to
be needed, but it could be written as well.)
We could add an unsigned short value (autosuspend_time) to
struct usb_interface as well as to struct usb_device, so that
individual interface drivers can specify a timeout value. Or
we could just let them modify the value in usb_device, which
would be a lot simpler.
This leaves open the question of what timeout value we should actually
use. If we have interface-specific values then clearly we want to use
their maximum. But should a value set via sysfs always take precedence?
How does this sound?
Alan Stern
-------------------------------------------------------------------------
Using Tomcat but need to do more? Need to support web services, security?
Get stuff done quickly with pre-integrated technology to make your job easier.
Download IBM WebSphere Application Server v.1.0.1 based on Apache Geronimo
http://sel.as-us.falkag.net/sel?cmd=lnk&kid=120709&bid=263057&dat=121642
_______________________________________________
linux-usb-devel@lists.sourceforge.net
To unsubscribe, use the last form field at:
https://lists.sourceforge.net/lists/listinfo/linux-usb-devel
