Hi Hao,

On Tue, Feb 13, 2018 at 05:24:35PM +0800, Wu Hao wrote:
> For feature devices, we need a method to find the port dedicated
> to the device. This patch adds a function fpga_cdev_find_port
> for this purpose. e.g FPGA Management Engine (FME) Partial
> Reconfiguration sub feature, it uses this function to find
> dedicated port on the device for PR function implementation.
> 
> Signed-off-by: Tim Whisonant <tim.whisonant@intel.com>
> Signed-off-by: Enno Luebbers <enno.luebbers@intel.com>
> Signed-off-by: Shiva Rao <shiva.rao@intel.com>
> Signed-off-by: Christopher Rauer <christopher.rauer@intel.com>
> Signed-off-by: Xiao Guangrong <guangrong.xiao@linux.intel.com>
> Signed-off-by: Wu Hao <hao.wu@intel.com>
Acked-by: Moritz Fischer <mdf@kernel.org>
> ---
> v3: s/fpga_for_each_port/fpga_cdev_find_port/
>     move fpga_cdev_find_port to fpga-dfl module.
> v4: improve description in commit message.
>     add comments to remind user to put_device after use this function.
> ---
>  drivers/fpga/dfl.c | 34 ++++++++++++++++++++++++++++++++++
>  drivers/fpga/dfl.h | 20 ++++++++++++++++++++
>  2 files changed, 54 insertions(+)
> 
> diff --git a/drivers/fpga/dfl.c b/drivers/fpga/dfl.c
> index dcfe5ab..38dc819 100644
> --- a/drivers/fpga/dfl.c
> +++ b/drivers/fpga/dfl.c
> @@ -783,6 +783,40 @@ void fpga_remove_feature_devs(struct fpga_cdev *cdev)
>  }
>  EXPORT_SYMBOL_GPL(fpga_remove_feature_devs);
>  
> +/**
> + * __fpga_cdev_find_port - find a port under given container device
> + *
> + * @cdev: container device
> + * @data: data passed to match function
> + * @match: match function used to find specific port from the port device list
> + *
> + * Find a port device under container device. This function needs to be
> + * invoked with lock held.
> + *
> + * This function returns NULL if the device doesn't match and non-zero if it
> + * does. If this function returns non-zero and a reference to the platform
> + * device of port can be obtained.
> + *
> + * NOTE: you will need to drop the device reference with put_device() after use.
> + */
> +struct platform_device *
> +__fpga_cdev_find_port(struct fpga_cdev *cdev, void *data,
> +		      int (*match)(struct platform_device *, void *))
> +{
> +	struct feature_platform_data *pdata;
> +	struct platform_device *port_dev;
> +
> +	list_for_each_entry(pdata, &cdev->port_dev_list, node) {
> +		port_dev = pdata->dev;
> +
> +		if (match(port_dev, data) && get_device(&port_dev->dev))
> +			return port_dev;
> +	}
> +
> +	return NULL;
> +}
> +EXPORT_SYMBOL_GPL(__fpga_cdev_find_port);
> +
>  int fpga_port_id(struct platform_device *pdev)
>  {
>  	void __iomem *base = get_feature_ioaddr_by_id(&pdev->dev,
> diff --git a/drivers/fpga/dfl.h b/drivers/fpga/dfl.h
> index 9b19399..d6ecda1 100644
> --- a/drivers/fpga/dfl.h
> +++ b/drivers/fpga/dfl.h
> @@ -356,4 +356,24 @@ struct fpga_cdev {
>  struct fpga_cdev *fpga_enumerate_feature_devs(struct fpga_enum_info *info);
>  void fpga_remove_feature_devs(struct fpga_cdev *cdev);
>  
> +/*
> + * need to drop the device reference with put_device() after use port platform
> + * device returned by __fpga_cdev_find_port and fpga_cdev_find_port functions.
> + */
> +struct platform_device *
> +__fpga_cdev_find_port(struct fpga_cdev *cdev, void *data,
> +		      int (*match)(struct platform_device *, void *));
> +
> +static inline struct platform_device *
> +fpga_cdev_find_port(struct fpga_cdev *cdev, void *data,
> +		    int (*match)(struct platform_device *, void *))
> +{
> +	struct platform_device *pdev;
> +
> +	mutex_lock(&cdev->lock);
> +	pdev = __fpga_cdev_find_port(cdev, data, match);
> +	mutex_unlock(&cdev->lock);
> +
> +	return pdev;
> +}
>  #endif /* __FPGA_DFL_H */
> -- 
> 2.7.4
> 

Thanks,
Moritz