Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753897AbcJ3UqE (ORCPT ); Sun, 30 Oct 2016 16:46:04 -0400 Received: from pandora.armlinux.org.uk ([78.32.30.218]:47522 "EHLO pandora.armlinux.org.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752479AbcJ3UqC (ORCPT ); Sun, 30 Oct 2016 16:46:02 -0400 Date: Sun, 30 Oct 2016 20:45:51 +0000 From: Russell King - ARM Linux To: Juri Lelli Cc: linux-kernel@vger.kernel.org, linux-pm@vger.kernel.org, linux-arm-kernel@lists.infradead.org, devicetree@vger.kernel.org, peterz@infradead.org, vincent.guittot@linaro.org, robh+dt@kernel.org, mark.rutland@arm.com, sudeep.holla@arm.com, lorenzo.pieralisi@arm.com, catalin.marinas@arm.com, will.deacon@arm.com, morten.rasmussen@arm.com, dietmar.eggemann@arm.com, broonie@kernel.org Subject: Re: [PATCH v7 REPOST 8/9] arm: add sysfs cpu_capacity attribute Message-ID: <20161030204551.GM1041@n2100.armlinux.org.uk> References: <20161017154650.18779-1-juri.lelli@arm.com> <20161017154650.18779-9-juri.lelli@arm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20161017154650.18779-9-juri.lelli@arm.com> User-Agent: Mutt/1.5.23 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3409 Lines: 115 On Mon, Oct 17, 2016 at 04:46:49PM +0100, Juri Lelli wrote: > +#ifdef CONFIG_PROC_SYSCTL > +#include > +#include Include files at the top of the file please. No need to ifdef them. They're sorted alphabetically, so new additions should be alphabetical. (That's a general rule - if something is already alphabetical, do not make it non-alphabetical.) > +static ssize_t show_cpu_capacity(struct device *dev, > + struct device_attribute *attr, > + char *buf) > +{ > + struct cpu *cpu = container_of(dev, struct cpu, dev); > + ssize_t rc; > + int cpunum = cpu->dev.id; > + unsigned long capacity = arch_scale_cpu_capacity(NULL, cpunum); > + > + rc = sprintf(buf, "%lu\n", capacity); > + > + return rc; Way too many lines for such a simple function. This can be simplified to just: struct cpu *cpu = container_of(dev, struct cpu, dev); return sprintf(buf, "%lu\n", arch_scale_cpu_capacity(NULL, cpu->dev.id); If you don't like the last line ending on column 79, then feel free to break it across two lines after the format string. > +} > + > +static ssize_t store_cpu_capacity(struct device *dev, > + struct device_attribute *attr, > + const char *buf, > + size_t count) > +{ > + struct cpu *cpu = container_of(dev, struct cpu, dev); > + int this_cpu = cpu->dev.id, i; > + unsigned long new_capacity; > + ssize_t ret; > + > + if (count) { > + char *p = (char *) buf; > + > + ret = kstrtoul(p, 0, &new_capacity); Unnecessary cast - kstrtoul takes a const char pointer, and in any case it's really bad form to cast away the "const-ness" of any pointer. So, just: if (count) { ret = kstrtoul(buf, 0, &new_capacity); should work just fine. > + if (ret) > + return ret; > + if (new_capacity > SCHED_CAPACITY_SCALE) > + return -EINVAL; > + > + mutex_lock(&cpu_scale_mutex); > + for_each_cpu(i, &cpu_topology[this_cpu].core_sibling) > + set_capacity_scale(i, new_capacity); > + mutex_unlock(&cpu_scale_mutex); > + } > + > + return count; > +} > + > +static DEVICE_ATTR(cpu_capacity, > + 0644, > + show_cpu_capacity, > + store_cpu_capacity); There's a move to use the named DEVICE_ATTR_RW() for this kind of thing, it'll want the functions named xxx_show() and xxx_store(). I see there's some recent patches to do this conversion across the kernel, so this should probably be done before submission. > + > +static int register_cpu_capacity_sysctl(void) > +{ > + int i; > + struct device *cpu; > + > + for_each_possible_cpu(i) { > + cpu = get_cpu_device(i); > + if (!cpu) { > + pr_err("%s: too early to get CPU%d device!\n", > + __func__, i); > + continue; > + } > + device_create_file(cpu, &dev_attr_cpu_capacity); > + } > + > + return 0; > +} > +late_initcall(register_cpu_capacity_sysctl); Hmm, this is really weird. topology_init() in arch/arm/kernel/setup.c is where these devices get created, and they're created at subsys_initcall() time. By that point, the list of possible CPUs has to be static, it's not going to change. I don't see why this has to be done at late_initcall() - and since topology.c will be linked after setup.c, I don't see why it shouldn't be at subsys_initcall() level to follow on after topology_init(). -- RMK's Patch system: http://www.armlinux.org.uk/developer/patches/ FTTC broadband for 0.8mile line: currently at 9.6Mbps down 400kbps up according to speedtest.net.