linux-kernel - Re: [PATCH] platform: set of_node in platform_device_register

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Date:   Wed, 20 Feb 2019 12:51:17 +0100
From:   Johan Hovold <johan@...nel.org>
To:     Mans Rullgard <mans@...sr.com>
Cc:     "Rafael J. Wysocki" <rafael@...nel.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] platform: set of_node in platform_device_register_full()

On Wed, Feb 20, 2019 at 11:35:06AM +0000, Mans Rullgard wrote:
> If the provided fwnode is an OF node, set dev.of_node as well.
> 
> Some drivers are just shims that create extra "glue" devices with the
> DT device as parent and have the real driver bind to these.  In these
> cases, the glue device needs to get a reference to the original DT node
> in order for the main driver to access properties and child nodes.
> 
> For example, the sunxi-musb driver creates such a glue device using
> platform_device_register_full().  Consequently, devices attached to
> this USB interface don't get associated with DT nodes, if present,
> the way they do with EHCI.
> 
> This change will allow sunxi-musb and similar driver to easily
> propagate the DT node to child devices as required.

Just a drive-by comment, didn't look to closely at this patch, but this
all sounds familiar.

Note that if both platform devices are bound to drivers you may end up
with some resources like pinctrl which are handled automatically by
driver core at probe time to be requested twice (and failing the second
time).

Take a look at 4e75e1d7dac9 ("driver core: add helper to reuse a
device-tree node"), which provides a means to avoid this, and
49484abd93ab ("USB: musb: dsps: propagate device-tree node").

> Signed-off-by: Mans Rullgard <mans@...sr.com>
> ---
>  drivers/base/platform.c | 1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/drivers/base/platform.c b/drivers/base/platform.c
> index dff82a3c2caa..853a1d0e5845 100644
> --- a/drivers/base/platform.c
> +++ b/drivers/base/platform.c
> @@ -512,6 +512,7 @@ struct platform_device *platform_device_register_full(
>  
>  	pdev->dev.parent = pdevinfo->parent;
>  	pdev->dev.fwnode = pdevinfo->fwnode;
> +	pdev->dev.of_node = of_node_get(to_of_node(pdev->dev.fwnode));
>  
>  	if (pdevinfo->dma_mask) {
>  		/*

Johan