On Mon, 30 Aug 2010, Oliver Neukum wrote: > Am Montag, 30. August 2010, 16:42:26 schrieb Alan Stern: > > Should we continue the convention (used in the USB subsystem) that > > negative values for suspend_delay will disable autosuspend? I'm not > > sure how useful that is, given that setting power/control to "on" has > > the same effect. > > > > Oliver, you originally argued strongly in favor of having both > > mechanisms. Do you still think they are both needed? > > Yes. We have drivers which probably cannot cope with a delay of 0. We wouldn't want 0 to disable autosuspend anyway; it's a valid number and many drivers _can_ cope with a delay of 0. > But you'd probably like the user to still be allowed to switch autosuspend > off for example to allow recharging battery powered devices. The user can turn off autosuspend by doing "echo on >/sys/.../power/control". Isn't that good enough? > Though the reason is not strong. I'd say it's better to keep both, > but not very important. IIRC your original argument had something to do with file access permissions for the attribute files. It's not clear that this is really an important issue now. Also, in the early development we needed a way to prevent the system from autosuspending devices that couldn't handle it; the solution was to set the default autosuspend delay to -1. That mechanism isn't needed now that we initialize most USB devices to the forbidden (i.e., power/control = "on") state. Alan Stern -- To unsubscribe from this list: send the line "unsubscribe linux-usb" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
