linux-kernel - Re: [PATCH 10/10] drivers: misc: use module_platform_driver

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Message-ID: <CAHkwnC-u=34CnHR5dH3qu6YeYyNcsmPfVORZFwtS4RYSjrVJ2g@mail.gmail.com>
Date:	Thu, 21 Mar 2013 14:10:17 +0100
From:	Fabio Porcedda <fabio.porcedda@...il.com>
To:	Arnd Bergmann <arnd@...db.de>
Cc:	Geert Uytterhoeven <geert@...ux-m68k.org>,
	H Hartley Sweeten <hartleys@...ionengravers.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	"linux-media@...r.kernel.org" <linux-media@...r.kernel.org>,
	"linux-ide@...r.kernel.org" <linux-ide@...r.kernel.org>,
	"lm-sensors@...sensors.org" <lm-sensors@...sensors.org>,
	"linux-input@...r.kernel.org" <linux-input@...r.kernel.org>,
	"linux-fbdev@...r.kernel.org" <linux-fbdev@...r.kernel.org>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Grant Likely <grant.likely@...retlab.ca>
Subject: Re: [PATCH 10/10] drivers: misc: use module_platform_driver_probe()

On Wed, Mar 20, 2013 at 12:46 PM, Arnd Bergmann <arnd@...db.de> wrote:
> On Wednesday 20 March 2013, Fabio Porcedda wrote:
>>
>> On Wed, Mar 20, 2013 at 11:20 AM, Arnd Bergmann <arnd@...db.de> wrote:
>> > On Wednesday 20 March 2013, Fabio Porcedda wrote:
>> >> I think we can check inside the  deferred_probe_work_func()
>> >> if the dev->probe function pointer is equal to platform_drv_probe_fail().
>> >
>> > I think it's too late by then, because that would only warn if we try to probe
>> > it again, but when platform_driver_probe() does not succeed immediately, it
>>
>> Maybe you mean "does succeed immediately" ?
>
> I mean in this code (simplified for the sake of discussion)
>
> int __init_or_module platform_driver_probe(struct platform_driver *drv,
>                 int (*probe)(struct platform_device *))
> {
>         int retval, code;
>
>         drv->probe = probe;
>         retval = code = platform_driver_register(drv);
>
>         drv->probe = NULL;
>         if (code == 0 && list_empty(&drv->driver.p->klist_devices.k_list))
>                 retval = -ENODEV;
>         drv->driver.probe = platform_drv_probe_fail;
>
>         if (code != retval)
>                 platform_driver_unregister(drv);
>         return retval;
> }
>
> we assume that all devices are bound to drivers during the call to
> platform_driver_register, and if the device list is empty afterwards,
> we unregister the driver and will never get to the deferred probing
> stage.

Thanks for the explanation, I understand now that is not that simple.

I was hoping it was easier.

Regards
--
Fabio Porcedda
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