Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::3:7 as permitted sender) client-ip=2620:137:e000::3:7;
Date:   Tue, 24 Oct 2023 18:32:40 +0300
From:   Andy Shevchenko <andriy.shevchenko@linux.intel.com>
To:     Russell King <rmk+kernel@armlinux.org.uk>
Cc:     linux-pm@vger.kernel.org, loongarch@lists.linux.dev,
        linux-acpi@vger.kernel.org, linux-arch@vger.kernel.org,
        linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org,
        linux-riscv@lists.infradead.org, kvmarm@lists.linux.dev,
        x86@kernel.org, linux-csky@vger.kernel.org,
        linux-doc@vger.kernel.org, linux-ia64@vger.kernel.org,
        linux-parisc@vger.kernel.org, Salil Mehta <salil.mehta@huawei.com>,
        Jean-Philippe Brucker <jean-philippe@linaro.org>,
        jianyong.wu@arm.com, justin.he@arm.com,
        James Morse <james.morse@arm.com>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        "Rafael J. Wysocki" <rafael@kernel.org>,
        Yury Norov <yury.norov@gmail.com>,
        Rasmus Villemoes <linux@rasmusvillemoes.dk>,
        Thomas Gleixner <tglx@linutronix.de>,
        Peter Zijlstra <peterz@infradead.org>
Subject: Re: [PATCH 38/39] cpumask: Add enabled cpumask for present CPUs that
 can be brought online
Message-ID: <ZTfjmM3nmeh+D5w/@smile.fi.intel.com>
References: <ZTffkAdOqL2pI2la@shell.armlinux.org.uk>
 <E1qvJBk-00AqSW-R8@rmk-PC.armlinux.org.uk>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <E1qvJBk-00AqSW-R8@rmk-PC.armlinux.org.uk>
Organization: Intel Finland Oy - BIC 0357606-4 - Westendinkatu 7, 02160 Espoo
Precedence: bulk

On Tue, Oct 24, 2023 at 04:19:24PM +0100, Russell King wrote:
> From: James Morse <james.morse@arm.com>
> 
> The 'offline' file in sysfs shows all offline CPUs, including those
> that aren't present. User-space is expected to remove not-present CPUs
> from this list to learn which CPUs could be brought online.
> 
> CPUs can be present but not-enabled. These CPUs can't be brought online
> until the firmware policy changes, which comes with an ACPI notification
> that will register the CPUs.
> 
> With only the offline and present files, user-space is unable to
> determine which CPUs it can try to bring online. Add a new CPU mask
> that shows this based on all the registered CPUs.

...

> +static ssize_t print_cpus_enabled(struct device *dev,
> +				  struct device_attribute *attr, char *buf)
> +{
> +	return sysfs_emit(buf, "%*pbl\n", cpumask_pr_args(cpu_enabled_mask));
> +}
> +static DEVICE_ATTR(enabled, 0444, print_cpus_enabled, NULL);

Hmm... DEVICE_ATTR_RO() ?

-- 
With Best Regards,
Andy Shevchenko