Re: [PATCH 38/39] cpumask: Add enabled cpumask for present CPUs that can be brought online

Andy Shevchenko <[email protected]> Tue, 24 Oct 2023 18:32:40 +0300

Newsgroups	gmane.linux.ports.parisc,gmane.linux.power-management.general,gmane.linux.acpi.devel,gmane.linux.kernel.cross-arch,gmane.linux.kernel,gmane.linux.ports.arm.kernel,gmane.linux.ports.riscv,gmane.linux.documentation,gmane.linux.ports.ia64
Organization	Intel Finland Oy - BIC 0357606-4 - Westendinkatu 7, 02160 Espoo
Message-ID	<ZTfjmM3nmeh+D5w/@smile.fi.intel.com>

On Tue, Oct 24, 2023 at 04:19:24PM +0100, Russell King wrote:
> From: James Morse <[email protected]>
> 
> 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