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

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Date:	Tue, 22 Sep 2015 08:45:51 +0200
From:	Tomeu Vizoso <tomeu.vizoso@...labora.com>
To:	Rob Herring <robh@...nel.org>
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 22 September 2015 at 02:39, Rob Herring <robh@...nel.org> wrote:
> 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.

Yeah, Intel's 0day build bot warned of the missing get_device() when
running the OF unittests.

Regards,

Tomeu

> Rob
> --
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