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

[Tomeu Vizoso]

On 22 October 2015 at 03:02, Rafael J. Wysocki <rjw@xxxxxxxxxxxxx> wrote:
> On Monday, September 21, 2015 04:02:43 PM Tomeu Vizoso 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@xxxxxxxxxxxxx>
>> ---
>>
>> 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))
>> +             return to_platform_device(np->device);
>> +     return NULL;
>>  }
>>  EXPORT_SYMBOL(of_find_device_by_node);
>>
>> @@ -192,6 +187,8 @@ static struct platform_device *of_platform_device_create_pdata(
>>               goto err_clear_flag;
>>       }
>>
>> +     np->device = &dev->dev;
>> +
>>       return dev;
>>
>>  err_clear_flag:
>> @@ -272,6 +269,8 @@ static struct amba_device *of_amba_device_create(struct device_node *node,
>>               goto err_free;
>>       }
>>
>> +     node->device = &dev->dev;
>> +
>>       return dev;
>>
>>  err_free:
>> @@ -476,6 +475,8 @@ static int of_platform_device_destroy(struct device *dev, void *data)
>>       if (of_node_check_flag(dev->of_node, OF_POPULATED_BUS))
>>               device_for_each_child(dev, NULL, of_platform_device_destroy);
>>
>> +     dev->of_node->device = NULL;
>> +
>>       if (dev->bus == &platform_bus_type)
>>               platform_device_unregister(to_platform_device(dev));
>>  #ifdef CONFIG_ARM_AMBA
>> diff --git a/include/linux/of.h b/include/linux/of.h
>> index 2194b8ca41f9..eb091be0f8ee 100644
>> --- a/include/linux/of.h
>> +++ b/include/linux/of.h
>> @@ -52,6 +52,7 @@ struct device_node {
>>       phandle phandle;
>>       const char *full_name;
>>       struct fwnode_handle fwnode;
>> +     struct device *device;
>
> There are cases in which multiple device objects point to the same device_node,
> so is the single struct device pointer here really sufficient?

Only one struct device is registered for a given DT device node when
the DT is scanned (otherwise, of_find_device_by_node wouldn't be
safe).

If some driver makes a struct device to point to a device_node that
already has a struct device associated with it, that's fine.

Regards,

Tomeu

>>
>>       struct  property *properties;
>>       struct  property *deadprops;    /* removed properties */
>>
>
> Thanks,
> Rafael
>
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