linux-kernel - Re: [PATCH v2 1/8] iio: proximity: ping: pass reference to IIO device via call-stack

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Date:   Sat, 16 May 2020 18:12:44 +0100
From:   Jonathan Cameron <jic23@...nel.org>
To:     Alexandru Ardelean <alexandru.ardelean@...log.com>
Cc:     <linux-iio@...r.kernel.org>,
        <linux-arm-kernel@...ts.infradead.org>,
        <linux-stm32@...md-mailman.stormreply.com>,
        <linux-kernel@...r.kernel.org>, <ludovic.desroches@...rochip.com>,
        <eugen.hristev@...rochip.com>, <nicolas.ferre@...rochip.com>,
        <alexandre.belloni@...tlin.com>, <alexandre.torgue@...com>,
        <mcoquelin.stm32@...il.com>, <ak@...klinger.de>
Subject: Re: [PATCH v2 1/8] iio: proximity: ping: pass reference to IIO
 device via call-stack

On Thu, 14 May 2020 16:17:03 +0300
Alexandru Ardelean <alexandru.ardelean@...log.com> wrote:

> Since there will be some changes to how iio_priv_to_dev() is implemented,
> it could be that the helper becomes a bit slower, as it will be hidden away
> in the IIO core.
> 
> For this driver, the IIO device can be passed directly as a parameter to
> the ping_read() function, thus making it immune to the change of
> iio_priv_to_dev().
> 
> Signed-off-by: Alexandru Ardelean <alexandru.ardelean@...log.com>

Patch makes sense and I should have spotted this one during original
review :( Going backwards and forwards is never a good idea even without
the rework you have.

But... (you knew that was coming :), there is no need to pass
data to the the read function.  It is the structure returned by
iio_priv() and not used anywhere else in the read_raw callback.
So might as well just pass the iio_dev and get the data structure
with in the read function via iio_priv(indio_dev)

Thanks,

J

> ---
>  drivers/iio/proximity/ping.c | 5 ++---
>  1 file changed, 2 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/iio/proximity/ping.c b/drivers/iio/proximity/ping.c
> index 12b893c5b0ee..ddc43a5a2ef8 100644
> --- a/drivers/iio/proximity/ping.c
> +++ b/drivers/iio/proximity/ping.c
> @@ -89,14 +89,13 @@ static irqreturn_t ping_handle_irq(int irq, void *dev_id)
>  	return IRQ_HANDLED;
>  }
>  
> -static int ping_read(struct ping_data *data)
> +static int ping_read(struct iio_dev *indio_dev, struct ping_data *data)
>  {
>  	int ret;
>  	ktime_t ktime_dt;
>  	s64 dt_ns;
>  	u32 time_ns, distance_mm;
>  	struct platform_device *pdev = to_platform_device(data->dev);
> -	struct iio_dev *indio_dev = iio_priv_to_dev(data);
>  
>  	/*
>  	 * just one read-echo-cycle can take place at a time
> @@ -236,7 +235,7 @@ static int ping_read_raw(struct iio_dev *indio_dev,
>  
>  	switch (info) {
>  	case IIO_CHAN_INFO_RAW:
> -		ret = ping_read(data);
> +		ret = ping_read(indio_dev, data);
>  		if (ret < 0)
>  			return ret;
>  		*val = ret;