linux-kernel - Re: [PATCH v5 18/48] mfd: twl4030-power: Register with kernel power-off handler

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Message-ID: <5460C70D.1000206@roeck-us.net>
Date:	Mon, 10 Nov 2014 06:09:17 -0800
From:	Guenter Roeck <linux@...ck-us.net>
To:	Pavel Machek <pavel@....cz>
CC:	linux-kernel@...r.kernel.org, linux-pm@...r.kernel.org,
	Samuel Ortiz <sameo@...ux.intel.com>,
	Lee Jones <lee.jones@...aro.org>, linux-omap@...r.kernel.org
Subject: Re: [PATCH v5 18/48] mfd: twl4030-power: Register with kernel power-off
 handler

On 11/10/2014 12:46 AM, Pavel Machek wrote:
> Hi!
>
>> @@ -611,7 +611,7 @@ twl4030_power_configure_resources(const struct twl4030_power_data *pdata)
>>    * After a successful execution, TWL shuts down the power to the SoC
>>    * and all peripherals connected to it.
>>    */
>> -void twl4030_power_off(void)
>> +static void twl4030_power_off(struct power_off_handler_block *this)
>>   {
>>   	int err;
>>
>> @@ -621,6 +621,11 @@ void twl4030_power_off(void)
>>   		pr_err("TWL4030 Unable to power off\n");
>>   }
>>
>> +static struct power_off_handler_block twl4030_power_off_hb = {
>> +	.handler = twl4030_power_off,
>> +	.priority = POWER_OFF_PRIORITY_LOW,
>> +};
>> +
>>   static bool twl4030_power_use_poweroff(const struct twl4030_power_data *pdata,
>>   					struct device_node *node)
>>   {
>> @@ -839,7 +844,9 @@ static int twl4030_power_probe(struct platform_device *pdev)
>>   	}
>>
>>   	/* Board has to be wired properly to use this feature */
>> -	if (twl4030_power_use_poweroff(pdata, node) && !pm_power_off) {
>> +	if (twl4030_power_use_poweroff(pdata, node)) {
>> +		int ret;
>> +
>>   		/* Default for SEQ_OFFSYNC is set, lets ensure this */
>>   		err = twl_i2c_read_u8(TWL_MODULE_PM_MASTER, &val,
>>   				      TWL4030_PM_MASTER_CFG_P123_TRANSITION);
>> @@ -856,7 +863,11 @@ static int twl4030_power_probe(struct platform_device *pdev)
>>   			}
>>   		}
>>
>> -		pm_power_off = twl4030_power_off;
>> +		ret = devm_register_power_off_handler(&pdev->dev,
>> +						      &twl4030_power_off_hb);
>> +		if (ret)
>> +			dev_warn(&pdev->dev,
>> +				 "Failed to register power-off handler\n");
>>   	}
>>
>
> Could we get rid of the "struct power_off_handler_block" and guarantee
> that register_power_off never fails (or print message from the
> register_power_off...)? That way, your patch would be an cleanup.
>
> You could then add priorities if they turn out to be really
> neccessary, later...

Priorities are necessary. We had _that_ discussion before.
Priorities solve the problem where multiple handlers are installed,
either conditionally or unconditionally. If I take priorities away,
a substantial part of the patch set's value gets lost, and I might
as well drop it.

Guenter

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