From patchwork Fri Jun 21 18:09:47 2013 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Gerhard Sittig X-Patchwork-Id: 2764011 Return-Path: X-Original-To: patchwork-linux-arm@patchwork.kernel.org Delivered-To: patchwork-parsemail@patchwork2.web.kernel.org Received: from mail.kernel.org (mail.kernel.org [198.145.19.201]) by patchwork2.web.kernel.org (Postfix) with ESMTP id 1FFADC0AB1 for ; Fri, 21 Jun 2013 18:55:53 +0000 (UTC) Received: from mail.kernel.org (localhost [127.0.0.1]) by mail.kernel.org (Postfix) with ESMTP id 08BF6201BF for ; Fri, 21 Jun 2013 18:55:52 +0000 (UTC) Received: from casper.infradead.org (casper.infradead.org [85.118.1.10]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id F2D902014E for ; Fri, 21 Jun 2013 18:55:50 +0000 (UTC) Received: from merlin.infradead.org ([2001:4978:20e::2]) by casper.infradead.org with esmtps (Exim 4.80.1 #2 (Red Hat Linux)) id 1Uq5qE-0007GX-9G; Fri, 21 Jun 2013 18:13:49 +0000 Received: from localhost ([::1] helo=merlin.infradead.org) by merlin.infradead.org with esmtp (Exim 4.80.1 #2 (Red Hat Linux)) id 1Uq5oi-0002BZ-82; Fri, 21 Jun 2013 18:12:12 +0000 Received: from mail-out.m-online.net ([212.18.0.9]) by merlin.infradead.org with esmtps (Exim 4.80.1 #2 (Red Hat Linux)) id 1Uq5nY-000239-3U for linux-arm-kernel@lists.infradead.org; Fri, 21 Jun 2013 18:11:02 +0000 Received: from frontend1.mail.m-online.net (unknown [192.168.8.180]) by mail-out.m-online.net (Postfix) with ESMTP id 3bcSc54Rhzz4KK27; Fri, 21 Jun 2013 20:10:13 +0200 (CEST) Received: from localhost (dynscan1.mnet-online.de [192.168.6.68]) by mail.m-online.net (Postfix) with ESMTP id 3bcSc53wQBzbbjs; Fri, 21 Jun 2013 20:10:13 +0200 (CEST) X-Virus-Scanned: amavisd-new at mnet-online.de Received: from mail.mnet-online.de ([192.168.8.180]) by localhost (dynscan1.mail.m-online.net [192.168.6.68]) (amavisd-new, port 10024) with ESMTP id CUhQn_9qyfgo; Fri, 21 Jun 2013 20:10:12 +0200 (CEST) X-Auth-Info: 7rCBPOs69KFf5OY9smOlB8aNpTyo1BC0BSuYYH7CuqY= Received: from localhost (kons-4d027c0a.pool.mediaWays.net [77.2.124.10]) by mail.mnet-online.de (Postfix) with ESMTPA; Fri, 21 Jun 2013 20:10:12 +0200 (CEST) From: Gerhard Sittig To: Dmitry Torokhov , linux-input@vger.kernel.org, devicetree-discuss@lists.ozlabs.org, linux-arm-kernel@lists.infradead.org, Chao Xie Subject: [PATCH v1 01/12] input: matrix-keypad: update devicetree binding doc Date: Fri, 21 Jun 2013 20:09:47 +0200 Message-Id: <1371838198-7327-2-git-send-email-gsi@denx.de> X-Mailer: git-send-email 1.7.10.4 In-Reply-To: <1371838198-7327-1-git-send-email-gsi@denx.de> References: <1371838198-7327-1-git-send-email-gsi@denx.de> X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20130621_141100_533419_9C0B192B X-CRM114-Status: GOOD ( 13.10 ) X-Spam-Score: -1.9 (-) Cc: Eric Miao , Detlev Zundel , Arnd Bergmann , Tony Lindgren , Gerhard Sittig , Sekhar Nori , Haojian Zhuang , Marek Vasut , Ralf Baechle , Anatolij Gustschin X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.15 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , MIME-Version: 1.0 Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+patchwork-linux-arm=patchwork.kernel.org@lists.infradead.org X-Spam-Status: No, score=-5.7 required=5.0 tests=BAYES_00, RCVD_IN_DNSWL_MED, RP_MATCHES_RCVD, UNPARSEABLE_RELAY autolearn=unavailable version=3.3.1 X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on mail.kernel.org X-Virus-Scanned: ClamAV using ClamSMTP update the device tree binding documentation for the GPIO matrix keypad driver: mention the driver's selecting all columns at once, reword the delay descriptions, add the missing active low GPIO pin level property Signed-off-by: Gerhard Sittig --- .../bindings/input/gpio-matrix-keypad.txt | 42 +++++++++++++++++--- 1 file changed, 36 insertions(+), 6 deletions(-) diff --git a/Documentation/devicetree/bindings/input/gpio-matrix-keypad.txt b/Documentation/devicetree/bindings/input/gpio-matrix-keypad.txt index ead641c..11d030e 100644 --- a/Documentation/devicetree/bindings/input/gpio-matrix-keypad.txt +++ b/Documentation/devicetree/bindings/input/gpio-matrix-keypad.txt @@ -2,9 +2,30 @@ GPIO driven matrix keypad is used to interface a SoC with a matrix keypad. The matrix keypad supports multiple row and column lines, a key can be -placed at each intersection of a unique row and a unique column. The matrix -keypad can sense a key-press and key-release by means of GPIO lines and -report the event using GPIO interrupts to the cpu. +placed at each intersection of a unique row and a unique column. + +Sampling the keypad status is done by individually activating column +lines (which thus are outputs) and reading back row lines (which are +inputs). Each combination of row and column is checked separately to +determine the status of a single key. + +To reduce load on the CPU, changes in the keys' status can get detected +by means of GPIO interrupts, which get generated upon changes in the pin +levels. This approach assumes that any change in the key press status +will result in a GPIO pin level change interrupt when all columns are +selected (active) at the same time. Which in turn assumes that all +column lines can get activated at the same time, and no harm is done to +the hardware when multiple keys are pressed simultaneously. + +Simple keypad matrix layouts just connect GPIO lines to mechanical +switches, with no other active components involved. Although due to the +driver's operation of activating all columns at the same time for most +of the time, the use of current limiting resistors may be desirable, or +column GPIO lines shall operate in open collector mode. + +More involved matrix layouts may include externally connected line +drivers and might influence signal polarity. The driver supports low +active signals, while high active line levels are assumed by default. Required Properties: - compatible: Should be "gpio-matrix-keypad" @@ -20,9 +41,18 @@ Required Properties: Optional Properties: - linux,no-autorepeat: do no enable autorepeat feature. - linux,wakeup: use any event on keypad as wakeup event. -- debounce-delay-ms: debounce interval in milliseconds -- col-scan-delay-us: delay, measured in microseconds, that is needed - before we can scan keypad after activating column gpio +- debounce-delay-ms: debounce interval in milliseconds, which needs + to pass between detecting a change in the key + press status and sampling the new status, e.g. + to support multi key presses without spurious + single key events, or to cope with bouncing + mechanical key switches +- col-scan-delay-us: delay interval in microseconds between selecting + a column line and reading back its row status, + such that pin levels can settle after + propagating through the matrix and its + associated hardware components +- gpio-activelow: row pins as well as column pins are active low Example: matrix-keypad {