From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-3.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS,USER_AGENT_GIT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 2475AC282C5 for ; Tue, 22 Jan 2019 21:18:32 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id F08B620870 for ; Tue, 22 Jan 2019 21:18:31 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726864AbfAVVSa (ORCPT ); Tue, 22 Jan 2019 16:18:30 -0500 Received: from mleia.com ([178.79.152.223]:58426 "EHLO mail.mleia.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726166AbfAVVS3 (ORCPT ); Tue, 22 Jan 2019 16:18:29 -0500 Received: from mail.mleia.com (localhost [127.0.0.1]) by mail.mleia.com (Postfix) with ESMTP id 7B1F343C8BF; Tue, 22 Jan 2019 21:18:26 +0000 (GMT) From: Vladimir Zapolskiy To: Linus Walleij Cc: linux-gpio@vger.kernel.org, linux-kernel@vger.kernel.org, Laurent Meunier , Masahiro Yamada , Russell King Subject: [PATCH v2 0/2] pinctrl: remove unused 'pinconf-config' debugfs interface Date: Tue, 22 Jan 2019 23:18:20 +0200 Message-Id: <20190122211822.7016-1-vz@mleia.com> X-Mailer: git-send-email 2.20.1 MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-49551924 X-CRM114-CacheID: sfid-20190122_211826_529769_16AD7941 X-CRM114-Status: GOOD ( 17.22 ) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org The main goal of the change is to remove .pin_config_dbg_parse_modify callback before a driver with its support appears. So far the in-kernel interface did not attract any users since its introduction 5 years ago. Originally .pin_config_dbg_parse_modify callback and the associated 'pinconf-config' debugfs file were introduced in commit f07512e615dd ("pinctrl/pinconfig: add debug interface"), a short description of 'pinconf-config' usage for debugging can be expressed this way: Write to 'pinconf-config' (see pinconf_dbg_config_write() function): % echo -n modify $map_type $device_name $state_name $pin_name $config > \ /sys/kernel/debug/pinctrl/$pinctrl/pinconf-config It supposes to update a global (therefore single!) 'pinconf_dbg_conf' variable with an alternative setting, the arguments should match an existing pinconf device and some registered pinctrl mapping 'map': * $map_type is either 'config_pin' or 'config_group', it should match 'map->type' value of PIN_MAP_TYPE_CONFIGS_PIN or PIN_MAP_TYPE_CONFIGS_GROUP accordingly, * $device_name should match 'map->dev_name' string value, * $state_name should match 'map->name' string value, * $pin_name should match 'map->data.configs.group_or_pin' string value, If all above has matched, then $config is a new value to be set by calling pinconfops->pin_config_dbg_parse_modify(pctldev, config, matched_config). After a successful write into 'pinconf-config' a user can read the file to get information about that single modified pin configuration. The fact is .pin_config_dbg_parse_modify callback has never been defined in 'struct pinconf_ops' of any pinconf driver, thus an actual modification of a pin or group state on any present pinconf controller does not happen, and it declares that all related code is no more than dead code. I discovered the issue while attempting to add .pin_config_dbg_parse_modify support in some drivers and found that too short 'MAX_NAME_LEN' set by drivers/pinctrl/pinconf.c:372:#define MAX_NAME_LEN 15 is practically insufficient to store a regular pinctrl device name, which are like 'e6060000.pin-controller-sh-pfc' or pin names like 'MX6QDL_PAD_ENET_REF_CLK', thus it is another indicator that the code is barely usable, insufficiently tested and unprepossessing. Of course it might be possible to increase MAX_NAME_LEN, and then add .pin_config_dbg_parse_modify callbacks to the drivers, but the whole idea of such a limited debug option looks inviable. A more flexible way to functionally substitute the original approach is to implicitly or explicitly use pinctrl_select_state() function whenever needed. The proposal is to remove the changes added by commit f07512e615dd ("pinctrl/pinconfig: add debug interface") for now, as described in patch 2/2 commit message it may affect only non-vanilla kernels formally. Note that still it is a debugfs UAPI change, which is supposed to be unstable, however, since 'pinconf-config' file is plainly unusable on vanilla, I won't expect any user reports or asks to restore it back, this my assumption nudges me not to add an RFC tag to the published change. Changes from v1 to v2: * added one patch against cirrus/pinctrl-madera-core.c to avoid a compile time warning due to a removed header inclusion Vladimir Zapolskiy (2): pinctrl: remove pinctrl/machine.h inclusion from pinctrl/pinconf.h pinctrl: remove unused 'pinconf-config' debugfs interface drivers/pinctrl/cirrus/pinctrl-madera-core.c | 1 + drivers/pinctrl/pinconf.c | 222 ------------------- include/linux/pinctrl/pinconf.h | 6 - 3 files changed, 1 insertion(+), 228 deletions(-) -- 2.20.1