linux-kernel - Re: [PATCH] thermal: of: look for sensor driver parent node if device node missing

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Date:	Wed, 30 Jul 2014 19:09:04 +0530
From:	Laxman Dewangan <ldewangan@...dia.com>
To:	Eduardo Valentin <edubezval@...il.com>,
	Lucas Stach <l.stach@...gutronix.de>
CC:	"rui.zhang@...el.com" <rui.zhang@...el.com>,
	"eduardo.valentin@...com" <eduardo.valentin@...com>,
	"linux-pm@...r.kernel.org" <linux-pm@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Stephen Warren <swarren@...dotorg.org>,
	Lee Jones <lee.jones@...aro.org>
Subject: Re: [PATCH] thermal: of: look for sensor driver parent node if device
 node missing

On Wednesday 30 July 2014 06:48 PM, Eduardo Valentin wrote:
> Laxman,
>
> On Mon, Jul 14, 2014 at 02:04:55PM +0200, Lucas Stach wrote:
>> Am Montag, den 14.07.2014, 16:42 +0530 schrieb Laxman Dewangan:
>>> There are some mfd devices which supports junction thermal interrupt
>>> like ams,AS3722. The DT binding of these devices are defined as the
>>> flat and drivers for sub module of such devices are registered as
>>> the mfd_add_devices. In this method, the sub devices registered as
>>> platform driver and these do not have the of_node pointer on their
>>> device structure. In this case, use the parent of_node pointer to
>>> get the required of_node pointer.
>>>
>>> Signed-off-by: Laxman Dewangan <ldewangan@...dia.com>
>>> ---
>>>   drivers/thermal/of-thermal.c | 2 ++
>>>   1 file changed, 2 insertions(+)
>>>
>>> diff --git a/drivers/thermal/of-thermal.c b/drivers/thermal/of-thermal.c
>>> index 04b1be7..85a7d71 100644
>>> --- a/drivers/thermal/of-thermal.c
>>> +++ b/drivers/thermal/of-thermal.c
>>> @@ -396,6 +396,8 @@ thermal_zone_of_sensor_register(struct device *dev, int sensor_id,
>>>   		return ERR_PTR(-EINVAL);
>>>   
>>>   	sensor_np = dev->of_node;
>>> +	if (!sensor_np && dev->parent)
>>> +		sensor_np = dev->parent->of_node;
>>>   
>>>   	for_each_child_of_node(np, child) {
>>>   		struct of_phandle_args sensor_specs;
>> This seems like the wrong way around. If the MFD has subdev information
>> stored in the parent node it should be the MFD drivers responsibility to
>> populate the subdev of_node with its own node. The subdev should not be
>> forced to make such possible unsafe assumptions.
>>
> This is my understanding too. MFD device drivers must populate the
> required data onto their sub devices while creating them.
>

Sometime ago, Stephen sent patch on MFD to initialize the mfd sub 
devices of_node with parent node.

mfd: always assign of_node in mfd_add_device()
http://lists.infradead.org/pipermail/linux-arm-kernel/2013-December/217482.html

But it has unforeseen issue and reverted with patch
mfd: Revert "mfd: Always assign of_node in mfd_add_device()"
https://groups.google.com/forum/#!msg/rtc-linux/2LeLipSPFs0/XfPCKpT1BnUJ

So we do not have any mechanism here to pass the parent of_node to the 
of-thermal.

Adding Stephen and Lee for more comment.
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