linux-kernel - Re: [PATCH] iio: light: ltr501: claim direct mode during select raw reads

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Message-ID: <a743ec96-28d6-64dd-bec8-369624728d3f@kernel.org>
Date:   Sat, 15 Oct 2016 16:10:03 +0100
From:   Jonathan Cameron <jic23@...nel.org>
To:     Alison Schofield <amsfield22@...il.com>
Cc:     knaack.h@....de, lars@...afoo.de, pmeerw@...erw.net,
        linux-iio@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] iio: light: ltr501: claim direct mode during select raw
 reads

On 11/10/16 20:56, Alison Schofield wrote:
> Driver was checking for direct mode but not locking it.  Use
> claim/release helper functions to guarantee the device stays
> in direct mode during required raw read cases.
> 
> Signed-off-by: Alison Schofield <amsfield22@...il.com>
The uneven levels of the claim and release in the second case
are nasty, please rework so that doesn't occur.

It will work as it is, but I'm feeling fussy ;)

Jonathan
> ---
>  drivers/iio/light/ltr501.c | 16 +++++++++++-----
>  1 file changed, 11 insertions(+), 5 deletions(-)
> 
> diff --git a/drivers/iio/light/ltr501.c b/drivers/iio/light/ltr501.c
> index 3afc53a..c2ac3cd 100644
> --- a/drivers/iio/light/ltr501.c
> +++ b/drivers/iio/light/ltr501.c
> @@ -631,14 +631,16 @@ static int ltr501_read_raw(struct iio_dev *indio_dev,
>  
>  	switch (mask) {
>  	case IIO_CHAN_INFO_PROCESSED:
> -		if (iio_buffer_enabled(indio_dev))
> -			return -EBUSY;
> -
>  		switch (chan->type) {
>  		case IIO_LIGHT:
> +			ret = iio_device_claim_direct_mode(indio_dev);
> +			if (ret)
> +				return ret;
> +
>  			mutex_lock(&data->lock_als);
>  			ret = ltr501_read_als(data, buf);
>  			mutex_unlock(&data->lock_als);
> +			iio_device_release_direct_mode(indio_dev);
>  			if (ret < 0)
>  				return ret;
>  			*val = ltr501_calculate_lux(le16_to_cpu(buf[1]),
> @@ -648,14 +650,16 @@ static int ltr501_read_raw(struct iio_dev *indio_dev,
>  			return -EINVAL;
>  		}
>  	case IIO_CHAN_INFO_RAW:
> -		if (iio_buffer_enabled(indio_dev))
> -			return -EBUSY;
> +		ret = iio_device_claim_direct_mode(indio_dev);
> +		if (ret)
> +			return ret;
>  
>  		switch (chan->type) {
>  		case IIO_INTENSITY:
>  			mutex_lock(&data->lock_als);
>  			ret = ltr501_read_als(data, buf);
>  			mutex_unlock(&data->lock_als);
> +			iio_device_release_direct_mode(indio_dev);
I don't like the releasing something in the case statement which was
taken outside of it.  Either bring the claim inside as you did
above, or rework this to do the release after the switch
for all paths.
>  			if (ret < 0)
>  				return ret;
>  			*val = le16_to_cpu(chan->address == LTR501_ALS_DATA1 ?
> @@ -665,11 +669,13 @@ static int ltr501_read_raw(struct iio_dev *indio_dev,
>  			mutex_lock(&data->lock_ps);
>  			ret = ltr501_read_ps(data);
>  			mutex_unlock(&data->lock_ps);
> +			iio_device_release_direct_mode(indio_dev);
>  			if (ret < 0)
>  				return ret;
>  			*val = ret & LTR501_PS_DATA_MASK;
>  			return IIO_VAL_INT;
>  		default:
> +			iio_device_release_direct_mode(indio_dev);
>  			return -EINVAL;
>  		}
>  	case IIO_CHAN_INFO_SCALE:
>