On Wed, Apr 30, 2008 at 11:28:59AM +0200, xerces8 wrote: > Hi! > > I'm curious about some details in the protocol used by USB mice. > A cursory look at the "Device Class Definition for HID 1.11" documents > tells me (note this is the first USB technical document I ever read) > that a mouse can tell the host the format (the protocol) used to report > data (movement, button state etc.). > > Also a quick look into linuxv2.6.25/drivers/hid/usbhid/usbmouse.c suggests > that 8 bits are used for position. > > So my questions are: > - is the position data always 8 bits wide ? No. The driver you need to look at is usbhid.ko, not usbmouse - that only works for the static "HID Boot Protocol", and is only useful in embedded devices. > - when are reports sent ? Are they polled by host ? Or sent by the device > on its own ? That depends on how you look at it. The host controller polls the device at a specified rate - typically 100Hz, but the device decides whether it will or won't send a report when polled. -- Vojtech Pavlik Director SuSE Labs -- To unsubscribe from this list: send the line "unsubscribe linux-input" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
