linux-kernel - Re: [PATCH v1 1/2] of: add devm_ functions for populate and depopulate

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Date:   Fri, 24 Feb 2017 16:26:22 +0100
From:   Benjamin Gaignard <benjamin.gaignard@...aro.org>
To:     Rob Herring <robh+dt@...nel.org>
Cc:     Frank Rowand <frowand.list@...il.com>,
        "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Vincent Abriou <vincent.abriou@...com>,
        dri-devel <dri-devel@...ts.freedesktop.org>,
        "linaro-kernel@...ts.linaro.org" <linaro-kernel@...ts.linaro.org>
Subject: Re: [PATCH v1 1/2] of: add devm_ functions for populate and depopulate

2017-02-24 16:20 GMT+01:00 Rob Herring <robh+dt@...nel.org>:
> On Fri, Feb 24, 2017 at 9:13 AM, Benjamin Gaignard
> <benjamin.gaignard@...aro.org> wrote:
>> 2017-02-24 15:17 GMT+01:00 Rob Herring <robh+dt@...nel.org>:
>>> On Fri, Feb 17, 2017 at 8:31 AM, Benjamin Gaignard
>>> <benjamin.gaignard@...aro.org> wrote:
>>>> Lost of calls to of_platform_populate() are not unbalanced by a call
>>>
>>> s/Lost/Lots/
>>>
>>>> to of_platform_depopulate(). This create issues while drivers are
>>>> bind/unbind.
>>>>
>>>> In way to solve those issues is to add devm_of_platform_populate()
>>>> which will call of_platform_depopulate() when the device is unbound
>>>> from the bus.
>>>
>>> One complication is of_platform_populate is designed to be called
>>> multiple times. We call it with the default match table and then
>>> platforms can call it again with a custom match table for example.
>>
>> I do not plan to use it every where but only in some drivers probe()
>> to avoid adding goto to call of_platform_depopulate() for each error
>> cases which may occur after calling populate.
>>
>>>
>>>> Signed-off-by: Benjamin Gaignard <benjamin.gaignard@...aro.org>
>>>> ---
>>>>  drivers/of/platform.c       | 77 +++++++++++++++++++++++++++++++++++++++++++++
>>>>  include/linux/of_platform.h | 20 ++++++++++++
>>>>  2 files changed, 97 insertions(+)
>>>>
>>>> diff --git a/drivers/of/platform.c b/drivers/of/platform.c
>>>> index b8064bc..3dbebf7 100644
>>>> --- a/drivers/of/platform.c
>>>> +++ b/drivers/of/platform.c
>>>> @@ -571,6 +571,83 @@ void of_platform_depopulate(struct device *parent)
>>>>  }
>>>>  EXPORT_SYMBOL_GPL(of_platform_depopulate);
>>>>
>>>> +static void devm_of_platform_populate_release(struct device *dev, void *res)
>>>> +{
>>>> +       of_platform_depopulate(*(struct device **)res);
>>>> +}
>>>> +
>>>> +/**
>>>> + * devm_of_platform_populate() - Populate platform_devices from device tree data
>>>> + * @dev: device that requested to populate from device tree data
>>>> + * @root: parent of the first level to probe or NULL for the root of the tree
>>>> + * @matches: match table, NULL to use the default
>>>
>>> NULL is no match table, not the default which means only populate
>>> immediate children.
>>
>> I have copy of_platform_populate() description...
>> I replace it by: @matches: match table (could be NULL)
>>
>>>
>>>> + * @lookup: auxdata table for matching id and platform_data with device nodes
>>>> + * @parent: parent to hook devices from, NULL for toplevel
>>>
>>> I think this needs to be a bit different args as the use is limited.
>>> root and parent must not be NULL. dev should be the same as parent.
>>> lookup was for legacy, so drop that.
>>
>> So function prototype will become:
>> int devm_of_platform_populate(struct device *dev, struct device_node
>> *root, const struct of_device_id *matches)
>
> I just noticed something else too. dev->of_node should equal root I
> think, so we can get rid of root param.

match parameter is very often set to NULL since this function will
have a limited
scope why not also remove it and only keep dev ?

>
> Rob