linux-kernel - Re: [RFC PATCH 1/7] drivers: base: Add resource managed version of delayed work init

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Date:   Sat, 13 Feb 2021 07:27:47 -0800
From:   Guenter Roeck <linux@...ck-us.net>
To:     Hans de Goede <hdegoede@...hat.com>,
        Matti Vaittinen <matti.vaittinen@...rohmeurope.com>,
        mazziesaccount@...il.com
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        "Rafael J. Wysocki" <rafael@...nel.org>,
        MyungJoo Ham <myungjoo.ham@...sung.com>,
        Chanwoo Choi <cw00.choi@...sung.com>,
        Andy Gross <agross@...nel.org>,
        Bjorn Andersson <bjorn.andersson@...aro.org>,
        Jean Delvare <jdelvare@...e.com>,
        Mark Gross <mgross@...ux.intel.com>,
        Sebastian Reichel <sre@...nel.org>,
        Chen-Yu Tsai <wens@...e.org>,
        Liam Girdwood <lgirdwood@...il.com>,
        Mark Brown <broonie@...nel.org>,
        Wim Van Sebroeck <wim@...ux-watchdog.org>,
        Saravana Kannan <saravanak@...gle.com>,
        Heikki Krogerus <heikki.krogerus@...ux.intel.com>,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        Joerg Roedel <jroedel@...e.de>,
        Dan Williams <dan.j.williams@...el.com>,
        Bartosz Golaszewski <bgolaszewski@...libre.com>,
        linux-kernel@...r.kernel.org, linux-arm-msm@...r.kernel.org,
        linux-hwmon@...r.kernel.org, platform-driver-x86@...r.kernel.org,
        linux-pm@...r.kernel.org, linux-watchdog@...r.kernel.org
Subject: Re: [RFC PATCH 1/7] drivers: base: Add resource managed version of
 delayed work init

On 2/13/21 7:03 AM, Hans de Goede wrote:
[ ... ]
> 
> I think something like this should work:
> 
> static int devm_delayed_work_autocancel(struct device *dev, struct delayed_work *w,
> 					void (*worker)(struct work_struct *work)) {
> 	INIT_DELAYED_WORK(w, worker);
> 	return devm_add_action(dev, (void (*action)(void *))cancel_delayed_work_sync, w);
> }
> 
> I'm not sure about the cast, that may need something like this instead:
> 
> typedef void (*devm_action_func)(void *);
> 
> static int devm_delayed_work_autocancel(struct device *dev, struct delayed_work *w,
> 					void (*worker)(struct work_struct *work)) {
> 	INIT_DELAYED_WORK(w, worker);
> 	return devm_add_action(dev, (devm_action_func)cancel_delayed_work_sync, w);

Unfortunately, you can not type cast function pointers in C. It is against the C ABI.
I am sure it is done in a few places in the kernel anyway, but those are wrong.

This is the reason why many calls to devm_add_action() point to functions such as

static void visconti_clk_disable_unprepare(void *data)
{
        clk_disable_unprepare(data);
}

which could otherwise be handled using typecasts.

Guenter