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=-5.3 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, USER_AGENT_SANE_1 autolearn=no 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 686CCC433E0 for ; Mon, 15 Feb 2021 09:25:22 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 221A664E07 for ; Mon, 15 Feb 2021 09:25:22 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230122AbhBOJZU (ORCPT ); Mon, 15 Feb 2021 04:25:20 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:44980 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230089AbhBOJZD (ORCPT ); Mon, 15 Feb 2021 04:25:03 -0500 Received: from metis.ext.pengutronix.de (metis.ext.pengutronix.de [IPv6:2001:67c:670:201:290:27ff:fe1d:cc33]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 3EA17C0613D6 for ; Mon, 15 Feb 2021 01:24:23 -0800 (PST) Received: from pty.hi.pengutronix.de ([2001:67c:670:100:1d::c5]) by metis.ext.pengutronix.de with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.92) (envelope-from ) id 1lBa75-0005Zp-Rx; Mon, 15 Feb 2021 10:24:15 +0100 Received: from ore by pty.hi.pengutronix.de with local (Exim 4.89) (envelope-from ) id 1lBa72-0000zq-6l; Mon, 15 Feb 2021 10:24:12 +0100 Date: Mon, 15 Feb 2021 10:24:12 +0100 From: Oleksij Rempel To: William Breathitt Gray Cc: jic23@kernel.org, kamel.bouhara@bootlin.com, gwendal@chromium.org, a.fatoum@pengutronix.de, david@lechnology.com, linux-iio@vger.kernel.org, patrick.havelange@essensium.com, alexandre.belloni@bootlin.com, mcoquelin.stm32@gmail.com, linux-kernel@vger.kernel.org, Dan Carpenter , kernel@pengutronix.de, fabrice.gasnier@st.com, syednwaris@gmail.com, linux-stm32@st-md-mailman.stormreply.com, linux-arm-kernel@lists.infradead.org, alexandre.torgue@st.com Subject: Re: [PATCH v8 17/22] counter: Add character device interface Message-ID: <20210215092412.ptbngqge7m7nyivp@pengutronix.de> References: <720278e3aaf3f249657ec18d158eca3f962baf8e.1613131238.git.vilhelm.gray@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <720278e3aaf3f249657ec18d158eca3f962baf8e.1613131238.git.vilhelm.gray@gmail.com> X-Sent-From: Pengutronix Hildesheim X-URL: http://www.pengutronix.de/ X-IRC: #ptxdist @freenode X-Accept-Language: de,en X-Accept-Content-Type: text/plain X-Uptime: 10:18:43 up 74 days, 23:25, 42 users, load average: 0.03, 0.08, 0.04 User-Agent: NeoMutt/20170113 (1.7.2) X-SA-Exim-Connect-IP: 2001:67c:670:100:1d::c5 X-SA-Exim-Mail-From: ore@pengutronix.de X-SA-Exim-Scanned: No (on metis.ext.pengutronix.de); SAEximRunCond expanded to false X-PTX-Original-Recipient: linux-kernel@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi William, On Fri, Feb 12, 2021 at 09:13:41PM +0900, William Breathitt Gray wrote: > This patch introduces a character device interface for the Counter > subsystem. Device data is exposed through standard character device read > operations. Device data is gathered when a Counter event is pushed by > the respective Counter device driver. Configuration is handled via ioctl > operations on the respective Counter character device node. ..... > +/** > + * counter_push_event - queue event for userspace reading > + * @counter: pointer to Counter structure > + * @event: triggered event > + * @channel: event channel > + * > + * Note: If no one is watching for the respective event, it is silently > + * discarded. > + */ > +void counter_push_event(struct counter_device *const counter, const u8 event, > + const u8 channel) > +{ > + struct counter_event ev = {0}; > + unsigned int copied = 0; > + unsigned long flags; > + struct counter_event_node *event_node; > + struct counter_comp_node *comp_node; > + > + ev.timestamp = ktime_get_ns(); > + ev.watch.event = event; > + ev.watch.channel = channel; > + > + /* Could be in an interrupt context, so use a raw spin lock */ > + raw_spin_lock_irqsave(&counter->events_list_lock, flags); > + > + /* Search for event in the list */ > + list_for_each_entry(event_node, &counter->events_list, l) > + if (event_node->event == event && > + event_node->channel == channel) > + break; > + > + /* If event is not in the list */ > + if (&event_node->l == &counter->events_list) > + goto exit_early; To cover my "interrupt-counter" use case, I added following line here to convert the tail drop fifo to the head drop fifo: + list_for_each_entry(comp_node, &event_node->comp_list, l) + to_copy += sizeof(ev); + + while (kfifo_avail(&counter->events) < to_copy) + kfifo_skip(&counter->events); May be it make sense to make it optional and integrate in to you patches before it goes mainline? Regards, Oleksij -- Pengutronix e.K. | | Steuerwalder Str. 21 | http://www.pengutronix.de/ | 31137 Hildesheim, Germany | Phone: +49-5121-206917-0 | Amtsgericht Hildesheim, HRA 2686 | Fax: +49-5121-206917-5555 |