linux-kernel - Re: [PATCH v8] platform: x86: Add ChromeOS ACPI device driver

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Message-ID: <YmUNnq5tH8mykNOF@kroah.com>
Date:   Sun, 24 Apr 2022 10:43:10 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     Muhammad Usama Anjum <usama.anjum@...labora.com>
Cc:     "Rafael J. Wysocki" <rafael@...nel.org>,
        Len Brown <lenb@...nel.org>,
        Hans de Goede <hdegoede@...hat.com>,
        Mark Gross <markgross@...nel.org>,
        Collabora Kernel ML <kernel@...labora.com>,
        groeck@...omium.org, bleung@...omium.org, dtor@...omium.org,
        gwendal@...omium.org, vbendeb@...omium.org, andy@...radead.org,
        Ayman Bagabas <ayman.bagabas@...il.com>,
        Benjamin Tissoires <benjamin.tissoires@...hat.com>,
        Blaž Hrastnik <blaz@...n.io>,
        Darren Hart <dvhart@...radead.org>,
        Dmitry Torokhov <dmitry.torokhov@...il.com>,
        Jeremy Soller <jeremy@...tem76.com>,
        Mattias Jacobsson <2pi@....nu>,
        Mauro Carvalho Chehab <mchehab+samsung@...nel.org>,
        Rajat Jain <rajatja@...gle.com>,
        Srinivas Pandruvada <srinivas.pandruvada@...ux.intel.com>,
        platform-driver-x86@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-acpi@...r.kernel.org,
        "Rafael J . Wysocki" <rafael.j.wysocki@...el.com>,
        Enric Balletbo i Serra <eballetbo@...il.com>
Subject: Re: [PATCH v8] platform: x86: Add ChromeOS ACPI device driver

On Fri, Apr 15, 2022 at 10:08:15PM +0500, Muhammad Usama Anjum wrote:
> +	i = 0;
> +	list_for_each_entry(aag, &chromeos_acpi.groups, list) {
> +		chromeos_acpi.dev_groups[i] = &aag->group;
> +		i++;
> +	}
> +
> +	ret = sysfs_create_groups(&dev->kobj, chromeos_acpi.dev_groups);

You have raced with userspace and lost here :(

Use the default groups pointer in the platform driver for this, and use
the is_visible() callback to know to show, or not show, the attribute
instead of building up dynamic lists of attributes at runtime.  That
will save you lots of crazy logic and housekeeping _AND_ userspace tools
will work properly as well.

thanks,

greg k-h