linux-kernel - Re: [PATCH v6 03/22] of/platform: Point to struct device from device node

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Date:	Mon, 21 Sep 2015 19:39:18 -0500
From:	Rob Herring <robh@...nel.org>
To:	Tomeu Vizoso <tomeu.vizoso@...labora.com>
Cc:	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Stephen Warren <swarren@...dotorg.org>,
	Javier Martinez Canillas <javier@....samsung.com>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Mark Brown <broonie@...nel.org>,
	Thierry Reding <thierry.reding@...il.com>,
	Alan Stern <stern@...land.harvard.edu>,
	"Rafael J. Wysocki" <rjw@...ysocki.net>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	Dmitry Torokhov <dmitry.torokhov@...il.com>,
	"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
	Linus Walleij <linus.walleij@...aro.org>,
	"linux-acpi@...r.kernel.org" <linux-acpi@...r.kernel.org>,
	Arnd Bergmann <arnd@...db.de>
Subject: Re: [PATCH v6 03/22] of/platform: Point to struct device from device node

On Mon, Sep 21, 2015 at 9:02 AM, Tomeu Vizoso
<tomeu.vizoso@...labora.com> wrote:
> When adding platform and AMBA devices, set the device node's device
> member to point to it.
>
> This speeds lookups considerably and is safe because we only create one
> of these devices for any given device node.
>
> Signed-off-by: Tomeu Vizoso <tomeu.vizoso@...labora.com>
> ---
>
> Changes in v5:
> - Set the pointer to struct device also for AMBA devices
> - Unset the pointer to struct device when the platform device is about
>   to be unregistered
> - Increase the reference count of the device before returning from
>   of_find_device_by_node()
>
>  drivers/of/platform.c | 19 ++++++++++---------
>  include/linux/of.h    |  1 +
>  2 files changed, 11 insertions(+), 9 deletions(-)
>
> diff --git a/drivers/of/platform.c b/drivers/of/platform.c
> index 1001efaedcb8..408d89f1d124 100644
> --- a/drivers/of/platform.c
> +++ b/drivers/of/platform.c
> @@ -32,11 +32,6 @@ const struct of_device_id of_default_bus_match_table[] = {
>         {} /* Empty terminated list */
>  };
>
> -static int of_dev_node_match(struct device *dev, void *data)
> -{
> -       return dev->of_node == data;
> -}
> -
>  /**
>   * of_find_device_by_node - Find the platform_device associated with a node
>   * @np: Pointer to device tree node
> @@ -45,10 +40,10 @@ static int of_dev_node_match(struct device *dev, void *data)
>   */
>  struct platform_device *of_find_device_by_node(struct device_node *np)
>  {
> -       struct device *dev;
> -
> -       dev = bus_find_device(&platform_bus_type, NULL, np, of_dev_node_match);
> -       return dev ? to_platform_device(dev) : NULL;
> +       if (np->device && np->device->bus == &platform_bus_type &&
> +           get_device(np->device))

Where do we drop the reference incremented by get_device?

However, bus_find_device also took a reference I think, so you aren't
really changing behavior.

Rob
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