linux-kernel - Re: [PATCH v4 06/24] fpga: dfl: adds fpga_cdev_find

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Message-ID: <CANk1AXQgeeQm_ncn+17nrjr+YTCKvpc=PVZEsaZVOjRb3aHTQQ@mail.gmail.com>
Date:   Wed, 14 Feb 2018 10:24:47 -0600
From:   Alan Tull <atull@...nel.org>
To:     Wu Hao <hao.wu@...el.com>
Cc:     Moritz Fischer <mdf@...nel.org>, linux-fpga@...r.kernel.org,
        linux-kernel <linux-kernel@...r.kernel.org>,
        linux-api@...r.kernel.org, "Kang, Luwei" <luwei.kang@...el.com>,
        "Zhang, Yi Z" <yi.z.zhang@...el.com>,
        Tim Whisonant <tim.whisonant@...el.com>,
        Enno Luebbers <enno.luebbers@...el.com>,
        Shiva Rao <shiva.rao@...el.com>,
        Christopher Rauer <christopher.rauer@...el.com>,
        Xiao Guangrong <guangrong.xiao@...ux.intel.com>
Subject: Re: [PATCH v4 06/24] fpga: dfl: adds fpga_cdev_find_port

On Tue, Feb 13, 2018 at 3:24 AM, Wu Hao <hao.wu@...el.com> wrote:

Hi Hao,

> 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.

OK, that is very clear now, thanks!  Ack with the minor doc changes below.

>
> Signed-off-by: Tim Whisonant <tim.whisonant@...el.com>
> Signed-off-by: Enno Luebbers <enno.luebbers@...el.com>
> Signed-off-by: Shiva Rao <shiva.rao@...el.com>
> Signed-off-by: Christopher Rauer <christopher.rauer@...el.com>
> Signed-off-by: Xiao Guangrong <guangrong.xiao@...ux.intel.com>
> Signed-off-by: Wu Hao <hao.wu@...el.com>
Acked-by: Alan Tull <atull@...nel.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.

Good but this would be more brief and more specific and more in line
with recommended format in Documentation/kernel-doc-nano-HOWTO.txt:

 * Return: pointer to port's platform device if successful, NULL otherwise.

> If this function returns non-zero and a reference to the platform
> + * device of port can be obtained.

This if..then type sentence is not complete (missing the 'then' part).
I see where you might have gotten inspiration for it from core.c.
Probably you could just delete the sentence and all would be clear.

> + *
> + * NOTE: you will need to drop the device reference with put_device() after use.
> + */

Good

Thanks,
Alan

> +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
>