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: <14fc4d7c-4ce7-e4ed-3e2e-400cbd16c071@microchip.com>
Date:   Tue, 14 Jun 2022 08:49:03 +0000
From:   <Claudiu.Beznea@...rochip.com>
To:     <jic23@...nel.org>
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 11.06.2022 20:54, Jonathan Cameron wrote:
> EXTERNAL EMAIL: Do not click links or open attachments unless you know the content is safe
> 
> 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.

OK, I'll give it a try. With this, would you prefer to still keep this patch?

> 
>> ---
>>  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?

Yep, this should have been missed...

> 
>> -             *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.

To be sure of what I've understood correctly: in the end you prefer to have
a patch with the point you suggested rather then the initial patch?

Thank you,
Claudiu Beznea

> 
>> +     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);
>