From mboxrd@z Thu Jan 1 00:00:00 1970 From: Nikolai Kondrashov Subject: Unit Exponent value storage Date: Wed, 09 Oct 2013 10:53:42 +0300 Message-ID: <52550B86.9070307@gmail.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Return-path: Received: from mail-wi0-f179.google.com ([209.85.212.179]:61441 "EHLO mail-wi0-f179.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751508Ab3JIHxq (ORCPT ); Wed, 9 Oct 2013 03:53:46 -0400 Received: by mail-wi0-f179.google.com with SMTP id hm2so462471wib.6 for ; Wed, 09 Oct 2013 00:53:45 -0700 (PDT) Sender: linux-input-owner@vger.kernel.org List-Id: linux-input@vger.kernel.org To: hidcomments@usb.org Cc: linux-input@vger.kernel.org Hello, Could you please clarify how the "Unit Exponent" global item value should be encoded in report descriptors, according to Device Class Definition for HID 1.11? In my understanding it is encoded similarly to the rest of the signed integer items, i.e. two's complement 1, 2, or 4 byte integer. However, the "HID Descriptor Tool" available on the HID page [1] encodes it as a two's complement nibble, limited to [-8, 7] range accordingly. Which encoding is meant by the specification? I'm CC'ing this message to the "linux-input" maillist where I'm trying to raise discussion about how "Unit Exponent" value should be interpreted for the purposes of resolution calculation for HID devices in the Linux kernel. Could you please keep this CC in your answer, so others get posted? Thank you very much. Sincerely, Nikolai Kondrashov