linux-kernel - Re: [PATCH v3 06/21] fpga: dfl: adds fpga_cdev_find

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Date:   Mon, 5 Feb 2018 16:08:19 -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 v3 06/21] fpga: dfl: adds fpga_cdev_find_port

On Mon, Nov 27, 2017 at 12:42 AM, Wu Hao <hao.wu@...el.com> wrote:

Hi Hao,

A couple comments below.

> For feature devices, e.g FPGA Management Engine (FME),

The first use I see of this function in this patchset is the FME PR,
not the FME, or am I misunderstanding?

> it may
> require fpga_cdev_find_port function to find dedicate port for
> further actions, so export this function from feature device
> driver module.

I understand the need for this function, but I'm having a hard time
following this explanation here.   Suggestion: "For feature devices,
we need a method to find the port dedicated to the device.  Add a
function fpga_cdev_find_port to do that"

>
> 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>
> ----
> v3: s/fpga_for_each_port/fpga_cdev_find_port/
>     move fpga_cdev_find_port to fpga-dfl module.
> ---
>  drivers/fpga/fpga-dfl.c | 27 +++++++++++++++++++++++++++
>  drivers/fpga/fpga-dfl.h | 16 ++++++++++++++++
>  2 files changed, 43 insertions(+)
>
> diff --git a/drivers/fpga/fpga-dfl.c b/drivers/fpga/fpga-dfl.c
> index 9294c0a..ce03b17 100644
> --- a/drivers/fpga/fpga-dfl.c
> +++ b/drivers/fpga/fpga-dfl.c
> @@ -873,6 +873,33 @@ 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.
> + */
> +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;

The caller will need to put the port_dev->dev.  Please document that
in the function header.  I mentioned that in v2.

Alan