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

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Date:   Fri, 24 Feb 2017 08:17:36 -0600
From:   Rob Herring <robh+dt@...nel.org>
To:     Benjamin Gaignard <benjamin.gaignard@...aro.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

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.

> 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.

> + * @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.

> + *
> + * Similar to of_platform_populate(), but will automatically call
> + * of_platform_depopulate() when the device is unbound from the bus.
> + *
> + * Returns 0 on success, < 0 on failure.
> + */