Messages in this thread | | | Date | Mon, 15 Jan 2007 11:36:38 -0500 (EST) | From | Alan Stern <> | Subject | Re: [linux-usb-devel] 2.6.20-rc4: usb somehow broken |
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On Mon, 15 Jan 2007, Oliver Neukum wrote:
> Am Montag, 15. Januar 2007 17:03 schrieb Alan Stern: > > On Mon, 15 Jan 2007, Oliver Neukum wrote: > > > > Upon further thought, a module parameter won't do as the problem > > > will arise without a driver loaded. A sysfs parameter turns the whole > > > affair into a race condition. Will you set the guard parameter before the > > > autosuspend logic strikes? > > > Unfortunately this leaves only the least attractive solution. > > > > There could be a mixed approach: a builtin blacklist that is extensible > > via a procfs- or sysfs-based interface. > > If you want to ask with a lot of bug reports which blacklist was loaded, > then we could.
This is a "damned-if-you-do, damned-if-you-don't" situation. Anyway, I've never liked the idea of loading up the kernel with a bunch of preset blacklist entries. For most users that are a waste of space, and unneeded entries almost never get removed.
> > Note that we actually have two problems to contend with. Some devices > > must never be autosuspended at all (they disconnect when resuming), and > > others need a reset after resuming. > > Do those who can be brought back with a reset need to be listed at all? > Error handling is not a bad idea.
The problem is that the system can't always tell that a reset is needed. There might be no symptoms at all. For example, I've got a USB keypad which doesn't work right after a resume -- key presses never get sent to the computer. As far as the system can tell the device is fine, though.
Alan Stern
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