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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 0567BC00528 for ; Thu, 3 Aug 2023 20:53:02 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232277AbjHCUwv (ORCPT ); Thu, 3 Aug 2023 16:52:51 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:56256 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229452AbjHCUwt (ORCPT ); Thu, 3 Aug 2023 16:52:49 -0400 X-Greylist: delayed 428 seconds by postgrey-1.37 at lindbergh.monkeyblade.net; Thu, 03 Aug 2023 13:52:47 PDT Received: from thorn.bewilderbeest.net (thorn.bewilderbeest.net [71.19.156.171]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id D826C11F for ; Thu, 3 Aug 2023 13:52:47 -0700 (PDT) Received: from hatter.bewilderbeest.net (63-228-114-1.tukw.qwest.net [63.228.114.1]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (4096 bits) server-digest SHA256) (No client certificate requested) (Authenticated sender: zev) by thorn.bewilderbeest.net (Postfix) with ESMTPSA id 3BAFE783; Thu, 3 Aug 2023 13:45:39 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=bewilderbeest.net; s=thorn; t=1691095539; bh=rqLvNnIUzrROBT5rajV36LBK+ny6+l2//bZ787j+lX4=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=mhL62TV2yHCgtCLXCMNy6nG3wukcImfjmhjBbDWP+XreY0GCrVku3IgD5CDWFhLD0 8UZLOMEpHD7qYEBrZPyiqgbhjJVMDb/gxuye1Ab2pKaBHewkppUYFM3ag6mYPSVxUR x3/MqJ8tP9SjEdzdci9DKx+SL++vEGK1xU84Jo7k= Date: Thu, 3 Aug 2023 13:45:37 -0700 From: Zev Weiss To: Naresh Solanki Cc: Liam Girdwood , Mark Brown , linux-kernel@vger.kernel.org Subject: Re: [PATCH] regulator: userspace-consumer: Add regulator event support Message-ID: References: <20230803111225.107572-1-Naresh.Solanki@9elements.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii; format=flowed Content-Disposition: inline In-Reply-To: <20230803111225.107572-1-Naresh.Solanki@9elements.com> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Aug 03, 2023 at 04:12:25AM PDT, Naresh Solanki wrote: >Add sysfs attribute to track regulator events received from regulator >notifier block handler. > Hi Naresh, Could you provide a bit more detail on how this is intended to be used? Some of the details (more below) seem a bit odd to me... >Signed-off-by: Naresh Solanki >--- > drivers/regulator/userspace-consumer.c | 52 +++++++++++++++++++++++++- > 1 file changed, 51 insertions(+), 1 deletion(-) > >diff --git a/drivers/regulator/userspace-consumer.c b/drivers/regulator/userspace-consumer.c >index 97f075ed68c9..a0b980022993 100644 >--- a/drivers/regulator/userspace-consumer.c >+++ b/drivers/regulator/userspace-consumer.c >@@ -29,6 +29,10 @@ struct userspace_consumer_data { > > int num_supplies; > struct regulator_bulk_data *supplies; >+ >+ struct kobject *kobj; >+ struct notifier_block nb; >+ unsigned long events; > }; > > static ssize_t name_show(struct device *dev, >@@ -89,12 +93,30 @@ static ssize_t state_store(struct device *dev, struct device_attribute *attr, > return count; > } > >+static DEFINE_MUTEX(events_lock); >+ >+static ssize_t events_show(struct device *dev, >+ struct device_attribute *attr, char *buf) >+{ >+ struct userspace_consumer_data *data = dev_get_drvdata(dev); >+ unsigned long e; >+ >+ mutex_lock(&events_lock); >+ e = data->events; >+ data->events = 0; ...particularly this bit -- a read operation on a read-only file (and especially one with 0644 permissions) having side-effects (clearing the value it accesses) seems on the face of it like fairly surprising behavior. Is this a pattern that's used elsewhere in any other sysfs files? >+ mutex_unlock(&events_lock); >+ >+ return sprintf(buf, "0x%lx\n", e); >+} >+ > static DEVICE_ATTR_RO(name); > static DEVICE_ATTR_RW(state); >+static DEVICE_ATTR_RO(events); New sysfs attributes should be documented in Documentation/ABI, which this appears to be missing. However, it looks like this would expose the values of all the REGULATOR_EVENT_* constants as a userspace-visible ABI -- is that something we really want to do? > > static struct attribute *attributes[] = { > &dev_attr_name.attr, > &dev_attr_state.attr, >+ &dev_attr_events.attr, > NULL, > }; > >@@ -115,12 +137,28 @@ static const struct attribute_group attr_group = { > .is_visible = attr_visible, > }; > >+static int regulator_userspace_notify(struct notifier_block *nb, >+ unsigned long event, >+ void *ignored) >+{ >+ struct userspace_consumer_data *data = >+ container_of(nb, struct userspace_consumer_data, nb); >+ >+ mutex_lock(&events_lock); >+ data->events |= event; >+ mutex_unlock(&events_lock); >+ Using a single global mutex (events_lock) to protect a single member of a per-device struct looks weird. Unless there's something subtle going on that I'm not seeing, it seems like the lock should be a member of the data struct instead of global, and since no blocking operations happen under it could it just be a spinlock? Or since it's just some simple updates to a single variable, why not just use an atomic_t and skip the lock entirely? >+ sysfs_notify(data->kobj, NULL, dev_attr_events.attr.name); >+ >+ return NOTIFY_OK; >+} >+ > static int regulator_userspace_consumer_probe(struct platform_device *pdev) > { > struct regulator_userspace_consumer_data tmpdata; > struct regulator_userspace_consumer_data *pdata; > struct userspace_consumer_data *drvdata; >- int ret; >+ int i, ret; > > pdata = dev_get_platdata(&pdev->dev); > if (!pdata) { >@@ -153,6 +191,7 @@ static int regulator_userspace_consumer_probe(struct platform_device *pdev) > drvdata->num_supplies = pdata->num_supplies; > drvdata->supplies = pdata->supplies; > drvdata->no_autoswitch = pdata->no_autoswitch; >+ drvdata->kobj = &pdev->dev.kobj; > > mutex_init(&drvdata->lock); > >@@ -186,6 +225,13 @@ static int regulator_userspace_consumer_probe(struct platform_device *pdev) > } > drvdata->enabled = !!ret; > >+ drvdata->nb.notifier_call = regulator_userspace_notify; >+ for (i = 0; i < drvdata->num_supplies; i++) { >+ ret = devm_regulator_register_notifier(drvdata->supplies[i].consumer, &drvdata->nb); >+ if (ret) >+ goto err_enable; >+ } >+ > return 0; > > err_enable: >@@ -197,6 +243,10 @@ static int regulator_userspace_consumer_probe(struct platform_device *pdev) > static int regulator_userspace_consumer_remove(struct platform_device *pdev) > { > struct userspace_consumer_data *data = platform_get_drvdata(pdev); >+ int i; >+ >+ for (i = 0; i < data->num_supplies; i++) >+ devm_regulator_unregister_notifier(data->supplies[i].consumer, &data->nb); > > sysfs_remove_group(&pdev->dev.kobj, &attr_group); > > >base-commit: 4fb53b2377c364e3753d6e293913b57dad68e98b >-- >2.41.0 >