Re: [PATCH 06/11] iio: pressure-core: st: Expand and renameLPS331AP's channel descriptor

[Lee Jones]

On Thu, 05 Sep 2013, Denis CIOCCA wrote:

> 
> >>> Due to the MACRO used, the task of reading, understanding and maintaining
> >>> the LPS331AP's channel descriptor is substantially difficult. This patch
> >>> is based on the view that it's better to have easy to read, maintainable
> >>> code than to save a few lines here and there. For that reason we're
> >>> expanding the array so initialisation is completed in full.
> >> Also for this one, the channel names are general and can be shared
> >> between different sensors. For the channel definition it's not a problem
> >> for me, but I think it's not necessary adds all that code...
> > I'm not sure what you mean by this. Would you be kind enough to
> > explain it in a different way please?
> The channel name (in this case st_press_channels) is not only specific 
> for one sensor but can be shared. Ok in this driver now is used only for 
> the lps331ap but for example in accelerometer driver is used by several 
> sensors. It's possible in the future for new pressure sensors use the 
> same channels definition.

Ah yes I see what you mean. Well as you say, for the moment, as
they're separated, this naming convention seems the most
appropriate. If we add anymore devices which share the definition, we
can pick the best naming convention for the situation I think. For
instance, I like that you've split the channels up into the number of
bits they support in the gyro and accel cases, so something of that
nature could be utilised if other device support is added.

> The channel definition is intended the switch by macro 
> ST_SENSORS_LSM_CHANNELS to the full definition, for me is not a problem 
> but I think it's not necessary.

If you are familiar with the macro I guess you could get used to
working with it, but coming from in as a first time reader, adding a
new device was pretty difficult. I had to look up the macro in the
header file, then have the original struct open too and cross
reference in 3 different places. It's made even more difficult by the
macro being in a different order to the original struct.

Now I've had time to work with it, I could probably work with it as
well. I was just thinking about helping out any new person that comes
along and tries to add support for a new sensor.

> >>> Signed-off-by: Lee Jones <lee.jones@xxxxxxxxxx>
> >>> ---
> >>>    drivers/iio/pressure/st_pressure_core.c | 45 +++++++++++++++++++++++++--------
> >>>    1 file changed, 34 insertions(+), 11 deletions(-)
> >>>
> >>> diff --git a/drivers/iio/pressure/st_pressure_core.c b/drivers/iio/pressure/st_pressure_core.c
> >>> index becfb25..7ba9299 100644
> >>> --- a/drivers/iio/pressure/st_pressure_core.c
> >>> +++ b/drivers/iio/pressure/st_pressure_core.c
> >>> @@ -58,16 +58,39 @@
> >>>    #define ST_PRESS_LPS331AP_OUT_XL_ADDR		0x28
> >>>    #define ST_TEMP_LPS331AP_OUT_L_ADDR		0x2b
> >>>    
> >>> -static const struct iio_chan_spec st_press_channels[] = {
> >>> -	ST_SENSORS_LSM_CHANNELS(IIO_PRESSURE,
> >>> +static const struct iio_chan_spec st_press_lsp331ap_channels[] = {
> >>> +	{
> >>> +		.type = IIO_PRESSURE,
> >>> +		.channel2 = IIO_NO_MOD,
> >>> +		.address = ST_PRESS_LPS331AP_OUT_XL_ADDR,
> >>> +		.scan_index = ST_SENSORS_SCAN_X,
> >>> +		.scan_type = {
> >>> +			.sign = 'u',
> >>> +			.realbits = 24,
> >>> +			.storagebits = 24,
> >>> +			.endianness = IIO_LE,
> >>> +		},
> >>> +		.info_mask_separate =
> >>>    			BIT(IIO_CHAN_INFO_RAW) | BIT(IIO_CHAN_INFO_SCALE),
> >>> -			ST_SENSORS_SCAN_X, 0, IIO_NO_MOD, 'u', IIO_LE, 24, 24,
> >>> -			ST_PRESS_LPS331AP_OUT_XL_ADDR),
> >>> -	ST_SENSORS_LSM_CHANNELS(IIO_TEMP,
> >>> -			BIT(IIO_CHAN_INFO_RAW) | BIT(IIO_CHAN_INFO_SCALE) |
> >>> -						BIT(IIO_CHAN_INFO_OFFSET),
> >>> -			-1, 0, IIO_NO_MOD, 's', IIO_LE, 16, 16,
> >>> -			ST_TEMP_LPS331AP_OUT_L_ADDR),
> >>> +		.modified = 0,
> >>> +	},
> >>> +	{
> >>> +		.type = IIO_TEMP,
> >>> +		.channel2 = IIO_NO_MOD,
> >>> +		.address = ST_TEMP_LPS331AP_OUT_L_ADDR,
> >>> +		.scan_index = -1,
> >>> +		.scan_type = {
> >>> +			.sign = 'u',
> >>> +			.realbits = 16,
> >>> +			.storagebits = 16,
> >>> +			.endianness = IIO_LE,
> >>> +		},
> >>> +		.info_mask_separate =
> >>> +			BIT(IIO_CHAN_INFO_RAW) |
> >>> +			BIT(IIO_CHAN_INFO_SCALE) |
> >>> +			BIT(IIO_CHAN_INFO_OFFSET),
> >>> +		.modified = 0,
> >>> +	},
> >>>    	IIO_CHAN_SOFT_TIMESTAMP(1)
> >>>    };
> >>>    
> >>> @@ -77,7 +100,7 @@ static const struct st_sensors st_press_sensors[] = {
> >>>    		.sensors_supported = {
> >>>    			[0] = LPS331AP_PRESS_DEV_NAME,
> >>>    		},
> >>> -		.ch = (struct iio_chan_spec *)st_press_channels,
> >>> +		.ch = (struct iio_chan_spec *)st_press_lsp331ap_channels,
> >>>    		.odr = {
> >>>    			.addr = ST_PRESS_LPS331AP_ODR_ADDR,
> >>>    			.mask = ST_PRESS_LPS331AP_ODR_MASK,
> >>> @@ -214,7 +237,7 @@ int st_press_common_probe(struct iio_dev *indio_dev)
> >>>    	pdata->num_data_channels = ST_PRESS_NUMBER_DATA_CHANNELS;
> >>>    	pdata->multiread_bit = pdata->sensor->multi_read_bit;
> >>>    	indio_dev->channels = pdata->sensor->ch;
> >>> -	indio_dev->num_channels = ARRAY_SIZE(st_press_channels);
> >>> +	indio_dev->num_channels = ARRAY_SIZE(st_press_lsp331ap_channels);
> >>>    
> >>>    	pdata->current_fullscale = (struct st_sensor_fullscale_avl *)
> >>>    						&pdata->sensor->fs.fs_avl[0];

-- 
Lee Jones
Linaro STMicroelectronics Landing Team Lead
Linaro.org â Open source software for ARM SoCs
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