From mboxrd@z Thu Jan 1 00:00:00 1970 From: Stefan Achatz Subject: HID: questions about polling rates Date: Fri, 12 Nov 2010 20:15:52 +0100 Message-ID: <1289589352.2629.95.camel@neuromancer> Reply-To: erazor_de@users.sourceforge.net Mime-Version: 1.0 Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 7bit Return-path: Received: from mail-in-18.arcor-online.net ([151.189.21.58]:43365 "EHLO mail-in-18.arcor-online.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932443Ab0KLTP4 (ORCPT ); Fri, 12 Nov 2010 14:15:56 -0500 Sender: linux-input-owner@vger.kernel.org List-Id: linux-input@vger.kernel.org To: Jiri Kosina , linux-input@vger.kernel.org, linux-kernel@vger.kernel.org, linux-usb@vger.kernel.orglinux-kernel@vger.kernel.org Hello, while working on my roccat device drivers I thought about the possiblity of on the fly polling rate changes and tested some things. First I tried different polling rates by writing values from 1 to 10 into /sys/bus/usb/drivers/usbhid/module/parameters/mousepoll. I observed that the polling rates seem to be capped on both sides. With value 1 I measure 2ms instead of 1ms with my hardware protocol analyzer. With 10 I get 8ms instead of 10ms. I only use cheap onboard usb controllers, but under windows they work with 1ms. A internet and code search revealed nothing regarding this to me. Is someone of you aware of this behaviour and could tell me more about it? Changing the polling rate of a device on the fly would requires to use usb_kill_urb() and usb_submit_urb() with new interval. To get the int_urb I would need additional informations for incomplete struct usbhid_device that lie in drivers/hid/usbhid/usbhid.h. My driver code is at home in drivers/hid/. Is it okay to include a header further down in the structure? Or does anyone have concerns about moving the mentioned header to include/linux? Is this a matter to follow at all? Thanks in advance Stefan