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

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Date:   Mon, 15 Feb 2021 07:22:51 +0000
From:   "Vaittinen, Matti" <Matti.Vaittinen@...rohmeurope.com>
To:     "hdegoede@...hat.com" <hdegoede@...hat.com>,
        "linux@...ck-us.net" <linux@...ck-us.net>
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Subject: Re: [RFC PATCH 1/7] drivers: base: Add resource managed version of
 delayed work init


On Sat, 2021-02-13 at 16:59 +0100, Hans de Goede wrote:
> Hi,
> 
> On 2/13/21 4:27 PM, Guenter Roeck wrote:
> > 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.
> 
> I see, bummer.

I think using devm_add_action() is still a good idea.

> 
> If we add a devm_clk_prepare_enable() helper that should probably be
> added
> to drivers/clk/clk-devres.c and not to drivers/base/devres.c .
> 
> I also still wonder if we cannot find a better place for this new
> devm_delayed_work_autocancel() helper but nothing comes to mind.

I don't like the idea of including device.h from workqueue.h - and I
think this would be necessary if we added
devm_delayed_work_autocancel() as inline in workqueue.h, right?

I also see strong objection towards the devm managed clean-ups.

How about adding some devm-helpers.c in drivers/base - where we could
collect devm-based helpers - and which could be enabled by own CONFIG -
and left out by those who dislike it?

I know I wrote that the devm_delayed_work_autocancel() does probably
not warrant own file - but if you can foresee devm_work_autocancel()
and few other generally useful helpers - then we would have a place for
those. The devm stuff should in my opinion live under drivers/.

Best Regards
	Matti Vaittinen