linux-kernel - Re: [PATCH 1/2] rtc: rtc-twl: Use devm

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Date:	Fri, 6 Dec 2013 16:53:01 +0200
From:	Grygorii Strashko <grygorii.strashko@...com>
To:	Jingoo Han <jg1.han@...sung.com>,
	"'Andrew Morton'" <akpm@...ux-foundation.org>
CC:	<linux-kernel@...r.kernel.org>,
	"'Alessandro Zummo'" <a.zummo@...ertech.it>,
	<rtc-linux@...glegroups.com>,
	"'Kevin Hilman'" <khilman@...aro.org>,
	"'Tony Lindgren'" <tony@...mide.com>,
	"'Peter Ujfalusi'" <peter.ujfalusi@...com>
Subject: Re: [PATCH 1/2] rtc: rtc-twl: Use devm_*() functions

On 12/06/2013 03:49 AM, Jingoo Han wrote:
> On Friday, December 06, 2013 1:51 AM, Grygorii Strashko wrote:
>> On 12/05/2013 03:03 AM, Jingoo Han wrote:
>>> Use devm_*() functions to make cleanup paths simpler, and remove
>>> unnecessary remove().
>>>
>>> Signed-off-by: Jingoo Han <jg1.han@...sung.com>
>>> ---
>>>    drivers/rtc/rtc-twl.c |   38 +++++++++++++-------------------------
>>>    1 file changed, 13 insertions(+), 25 deletions(-)
>>>
>>> diff --git a/drivers/rtc/rtc-twl.c b/drivers/rtc/rtc-twl.c
>>> index c2e80d7..1915464 100644
>>> --- a/drivers/rtc/rtc-twl.c
>>> +++ b/drivers/rtc/rtc-twl.c
>>> @@ -479,7 +479,7 @@ static int twl_rtc_probe(struct platform_device *pdev)
>>>    	u8 rd_reg;
>>>
>>>    	if (irq <= 0)
>>> -		goto out1;
>>> +		return ret;
>>>
>>>    	/* Initialize the register map */
>>>    	if (twl_class_is_4030())
>>> @@ -489,7 +489,7 @@ static int twl_rtc_probe(struct platform_device *pdev)
>>>
>>>    	ret = twl_rtc_read_u8(&rd_reg, REG_RTC_STATUS_REG);
>>>    	if (ret < 0)
>>> -		goto out1;
>>> +		return ret;
>>>
>>>    	if (rd_reg & BIT_RTC_STATUS_REG_POWER_UP_M)
>>>    		dev_warn(&pdev->dev, "Power up reset detected.\n");
>>> @@ -500,7 +500,7 @@ static int twl_rtc_probe(struct platform_device *pdev)
>>>    	/* Clear RTC Power up reset and pending alarm interrupts */
>>>    	ret = twl_rtc_write_u8(rd_reg, REG_RTC_STATUS_REG);
>>>    	if (ret < 0)
>>> -		goto out1;
>>> +		return ret;
>>>
>>>    	if (twl_class_is_6030()) {
>>>    		twl6030_interrupt_unmask(TWL6030_RTC_INT_MASK,
>>> @@ -512,7 +512,7 @@ static int twl_rtc_probe(struct platform_device *pdev)
>>>    	dev_info(&pdev->dev, "Enabling TWL-RTC\n");
>>>    	ret = twl_rtc_write_u8(BIT_RTC_CTRL_REG_STOP_RTC_M, REG_RTC_CTRL_REG);
>>>    	if (ret < 0)
>>> -		goto out1;
>>> +		return ret;
>>>
>>>    	/* ensure interrupts are disabled, bootloaders can be strange */
>>>    	ret = twl_rtc_write_u8(0, REG_RTC_INTERRUPTS_REG);
>>> @@ -522,34 +522,29 @@ static int twl_rtc_probe(struct platform_device *pdev)
>>>    	/* init cached IRQ enable bits */
>>>    	ret = twl_rtc_read_u8(&rtc_irq_bits, REG_RTC_INTERRUPTS_REG);
>>>    	if (ret < 0)
>>> -		goto out1;
>>> +		return ret;
>>>
>>>    	device_init_wakeup(&pdev->dev, 1);
>>>
>>> -	rtc = rtc_device_register(pdev->name,
>>> -				  &pdev->dev, &twl_rtc_ops, THIS_MODULE);
>>> +	rtc = devm_rtc_device_register(&pdev->dev, pdev->name,
>>> +					&twl_rtc_ops, THIS_MODULE);
>>>    	if (IS_ERR(rtc)) {
>>> -		ret = PTR_ERR(rtc);
>>>    		dev_err(&pdev->dev, "can't register RTC device, err %ld\n",
>>>    			PTR_ERR(rtc));
>>> -		goto out1;
>>> +		return PTR_ERR(rtc);
>>>    	}
>>>
>>> -	ret = request_threaded_irq(irq, NULL, twl_rtc_interrupt,
>>> -				   IRQF_TRIGGER_RISING | IRQF_ONESHOT,
>>> -				   dev_name(&rtc->dev), rtc);
>>> +	ret = devm_request_threaded_irq(&pdev->dev, irq, NULL,
>>> +					twl_rtc_interrupt,
>>> +					IRQF_TRIGGER_RISING | IRQF_ONESHOT,
>>> +					dev_name(&rtc->dev), rtc);
>>
>> Looks like this will change driver release order and free_irq
>> will be called after RTC device is unregistered.
>> I think, you need to request irq first -> then register RTC device.
>> Right?
>
> Hi Grygorii Strashko,
>
> No, free_irq() will be called before RTC device is unregistered.
>
> In probe(), the following functions are called as below:
>    1. devm_rtc_device_register() -> rtc_device_register()
>    2. devm_request_threaded_irq() -> request_threaded_irq()
>
> The release functions will be inversely called.
> When removing rtc-twl.
>    1. devm_irq_release() -> free_irq()
>    2. devm_rtc_device_release() -> rtc_device_unregister()
>
> Thus, it is safe.
> Thank you for your feedback. :-)
>

You are right. Sorry, my mistake :)

Regards,
-grygorii

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