linux-kernel - Re: [PATCH][v2] PM / sysfs: Expose suspend resume driver flags in sysfs

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Date:   Thu, 22 Oct 2020 16:36:25 +0300
From:   Andy Shevchenko <andy.shevchenko@...il.com>
To:     Chen Yu <yu.c.chen@...el.com>
Cc:     "Rafael J. Wysocki" <rjw@...ysocki.net>,
        Len Brown <len.brown@...el.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        Linux PM <linux-pm@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH][v2] PM / sysfs: Expose suspend resume driver flags in sysfs

On Thu, Oct 22, 2020 at 12:24 PM Chen Yu <yu.c.chen@...el.com> wrote:
>
> Currently there are 4 driver flags to control system suspend/resume
> behavior: DPM_FLAG_NO_DIRECT_COMPLETE, DPM_FLAG_SMART_PREPARE,
> DPM_FLAG_SMART_SUSPEND and DPM_FLAG_MAY_SKIP_RESUME. Make these flags
> visible in sysfs as read-only to get a brief understanding of the
> expected behavior of each device during suspend/resume, so as to
> facilitate suspend/resume debugging/tuning.
>
> For example:
> /sys/devices/pci0000:00/0000:00:15.1/power/driver_flags:4
> (DPM_FLAG_SMART_SUSPEND)
>
> /sys/devices/pci0000:00/0000:00:07.3/power/driver_flags:5
> (DPM_FLAG_NO_DIRECT_COMPLETE | DPM_FLAG_SMART_SUSPEND)

...

> +What:          /sys/devices/.../power/driver_flags
> +Date:          October 2020
> +Contact:       Chen Yu <yu.c.chen@...el.com>
> +Description:
> +               The /sys/devices/.../driver_flags attribute contains the driver
> +               flags to control system suspend/resume. The flag is a combination
> +               of DPM_FLAG_NO_DIRECT_COMPLETE, DPM_FLAG_SMART_PREPARE,
> +               DPM_FLAG_SMART_SUSPEND and DPM_FLAG_MAY_SKIP_RESUME, or 0 if the
> +               driver has not set any flag.

> This attribute is read-only. If
> +               CONFIG_PM_ADVANCED_DEBUG is not set this attribute is empty.

Which makes me wonder why we even expose this if the above is not set.

...

> +static struct attribute *pm_driver_flags_attrs[] = {
> +#ifdef CONFIG_PM_ADVANCED_DEBUG
> +#ifdef CONFIG_PM_SLEEP
> +       &dev_attr_driver_flags.attr,
> +#endif
> +#endif

> +       NULL,

No comma here, please. I think I commented on this internally.

> +};

-- 
With Best Regards,
Andy Shevchenko