linux-kernel - Re: [PATCH 07/16] iio: adc: at91-sama5d2_adc: simplify the code in at91_adc_read_info

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Message-ID: <20220611185403.3eaf9b65@jic23-huawei>
Date:   Sat, 11 Jun 2022 18:54:03 +0100
From:   Jonathan Cameron <jic23@...nel.org>
To:     Claudiu Beznea <claudiu.beznea@...rochip.com>
Cc:     <eugen.hristev@...rochip.com>, <lars@...afoo.de>,
        <nicolas.ferre@...rochip.com>, <alexandre.belloni@...tlin.com>,
        <robh+dt@...nel.org>, <krzk+dt@...nel.org>,
        <ludovic.desroches@...el.com>, <linux-iio@...r.kernel.org>,
        <linux-arm-kernel@...ts.infradead.org>,
        <devicetree@...r.kernel.org>, <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 07/16] iio: adc: at91-sama5d2_adc: simplify the code in
 at91_adc_read_info_raw()

On Thu, 9 Jun 2022 11:32:04 +0300
Claudiu Beznea <claudiu.beznea@...rochip.com> wrote:

> Simplify a bit the code in at91_adc_read_info_raw() by reducing the
> number of lines of code.
> 
> Signed-off-by: Claudiu Beznea <claudiu.beznea@...rochip.com>

I'm not convinced this is worth while, but there are some lesser
steps visible in this patch that probably are.

Given your earlier reorg to move at01_adc_adjust_val_osr() under the locks,
you can now move the locks to the caller, thus not needing to handle them
separately in all the exit paths.

> ---
>  drivers/iio/adc/at91-sama5d2_adc.c | 35 +++++++++---------------------
>  1 file changed, 10 insertions(+), 25 deletions(-)
> 
> diff --git a/drivers/iio/adc/at91-sama5d2_adc.c b/drivers/iio/adc/at91-sama5d2_adc.c
> index b52f1020feaf..fbb98e216e70 100644
> --- a/drivers/iio/adc/at91-sama5d2_adc.c
> +++ b/drivers/iio/adc/at91-sama5d2_adc.c
> @@ -1576,6 +1576,7 @@ static int at91_adc_read_info_raw(struct iio_dev *indio_dev,
>  				  struct iio_chan_spec const *chan, int *val)
>  {
>  	struct at91_adc_state *st = iio_priv(indio_dev);
> +	int (*fn)(struct at91_adc_state *, int, u16 *) = NULL;
>  	u16 tmp_val;
>  	int ret;
>  
> @@ -1583,29 +1584,18 @@ static int at91_adc_read_info_raw(struct iio_dev *indio_dev,
>  	 * Keep in mind that we cannot use software trigger or touchscreen
>  	 * if external trigger is enabled
>  	 */
> -	if (chan->type == IIO_POSITIONRELATIVE) {
> -		ret = iio_device_claim_direct_mode(indio_dev);
> -		if (ret)
> -			return ret;

You can drop this out of the if statements as it happens in all paths.
Or even better, move it to the caller..

> -		mutex_lock(&st->lock);
> -
> -		ret = at91_adc_read_position(st, chan->channel,
> -					     &tmp_val);

huh? ret not checked? 

> -		*val = tmp_val;
> -		ret = at91_adc_adjust_val_osr(st, val);
Sure this is duplicated, but meh it's only a few lines.


> -		mutex_unlock(&st->lock);
> -		iio_device_release_direct_mode(indio_dev);

this early release (compared to the long path) is the only bit really
gets duplicated in all paths..

> +	if (chan->type == IIO_POSITIONRELATIVE)
> +		fn = at91_adc_read_position;
> +	if (chan->type == IIO_PRESSURE)
> +		fn = at91_adc_read_pressure;
>  
> +	ret = iio_device_claim_direct_mode(indio_dev);
> +	if (ret)
>  		return ret;
> -	}
> -	if (chan->type == IIO_PRESSURE) {
this should always have been an else if () as the chan->type couldn't be both.

> -		ret = iio_device_claim_direct_mode(indio_dev);
> -		if (ret)
> -			return ret;
> -		mutex_lock(&st->lock);
hence this lot can be shared with the above.

> +	mutex_lock(&st->lock);
>  
> -		ret = at91_adc_read_pressure(st, chan->channel,
> -					     &tmp_val);
> +	if (fn) {
> +		ret = fn(st, chan->channel, &tmp_val);
>  		*val = tmp_val;
>  		ret = at91_adc_adjust_val_osr(st, val);
>  		mutex_unlock(&st->lock);
> @@ -1616,11 +1606,6 @@ static int at91_adc_read_info_raw(struct iio_dev *indio_dev,
>  
>  	/* in this case we have a voltage channel */
>  
> -	ret = iio_device_claim_direct_mode(indio_dev);
> -	if (ret)
> -		return ret;
> -	mutex_lock(&st->lock);
> -
>  	st->chan = chan;
>  
>  	at91_adc_cor(st, chan);