linux-kernel - Re: [PATCH v3 1/5] iio: mxs-lradc: change the realbits to 12

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Date:	Tue, 13 Aug 2013 22:24:27 +0100
From:	Jonathan Cameron <jic23@...nel.org>
To:	Hector Palacios <hector.palacios@...i.com>
CC:	linux-iio@...r.kernel.org, linux-kernel@...r.kernel.org,
	devicetree-discuss@...ts.ozlabs.org,
	alexandre.belloni@...e-electrons.com, lars@...afoo.de,
	fabio.estevam@...escale.com, marex@...x.de
Subject: Re: [PATCH v3 1/5] iio: mxs-lradc: change the realbits to 12

On 07/22/13 15:03, Hector Palacios wrote:
> The LRADC virtual channels have an 18 bit field to store the sum of up
> to 2^5 accumulated samples. The read_raw function however only operates
> over a single sample (12 bit resolution).
> In order to use this field for scaling operations, we need it to be the
> exact resolution value of the LRADC.
> Besides, the driver was using an 18 bit mask (LRADC_CH_VALUE_MASK) to
> report touch coordinates to userland. A 12 bit mask should be used instead
> or else the touch libraries will expect a coordinates range between 0
> and 0x3ffff (18 bits), instead of between 0 and 0xfff (12 bits).
> 
> Signed-off-by: Hector Palacios <hector.palacios@...i.com>
> Acked-by: Marek Vasut <marex@...x.de>
> Acked-by: Alexandre Belloni <alexandre.belloni@...e-electrons.com>
Applied to the togreg branch of iio.git

Thanks,

Jonathan
> ---
>  drivers/staging/iio/adc/mxs-lradc.c | 12 ++++++++----
>  1 file changed, 8 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/staging/iio/adc/mxs-lradc.c b/drivers/staging/iio/adc/mxs-lradc.c
> index 9f52a28..56667da 100644
> --- a/drivers/staging/iio/adc/mxs-lradc.c
> +++ b/drivers/staging/iio/adc/mxs-lradc.c
> @@ -225,6 +225,9 @@ struct mxs_lradc {
>  #define	LRADC_CTRL4_LRADCSELECT_MASK(n)		(0xf << ((n) * 4))
>  #define	LRADC_CTRL4_LRADCSELECT_OFFSET(n)	((n) * 4)
>  
> +#define LRADC_RESOLUTION			12
> +#define LRADC_SINGLE_SAMPLE_MASK		((1 << LRADC_RESOLUTION) - 1)
> +
>  /*
>   * Raw I/O operations
>   */
> @@ -540,9 +543,10 @@ static int mxs_lradc_ts_register(struct mxs_lradc *lradc)
>  	__set_bit(EV_ABS, input->evbit);
>  	__set_bit(EV_KEY, input->evbit);
>  	__set_bit(BTN_TOUCH, input->keybit);
> -	input_set_abs_params(input, ABS_X, 0, LRADC_CH_VALUE_MASK, 0, 0);
> -	input_set_abs_params(input, ABS_Y, 0, LRADC_CH_VALUE_MASK, 0, 0);
> -	input_set_abs_params(input, ABS_PRESSURE, 0, LRADC_CH_VALUE_MASK, 0, 0);
> +	input_set_abs_params(input, ABS_X, 0, LRADC_SINGLE_SAMPLE_MASK, 0, 0);
> +	input_set_abs_params(input, ABS_Y, 0, LRADC_SINGLE_SAMPLE_MASK, 0, 0);
> +	input_set_abs_params(input, ABS_PRESSURE, 0, LRADC_SINGLE_SAMPLE_MASK,
> +			     0, 0);
>  
>  	lradc->ts_input = input;
>  	input_set_drvdata(input, lradc);
> @@ -817,7 +821,7 @@ static const struct iio_buffer_setup_ops mxs_lradc_buffer_ops = {
>  	.channel = (idx),					\
>  	.scan_type = {						\
>  		.sign = 'u',					\
> -		.realbits = 18,					\
> +		.realbits = LRADC_RESOLUTION,			\
>  		.storagebits = 32,				\
>  	},							\
>  }
> 
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