Re: [PATCH v3 3/8] drivers:input:tsc2007: add iio interface to read external ADC input, temperature and raw conversion values

[H. Nikolaus Schaller]

Hi Jonathan,

> Am 24.09.2016 um 18:07 schrieb Jonathan Cameron <jic23@xxxxxxxxxx>:
> 
> On 23/09/16 13:41, H. Nikolaus Schaller wrote:
>> The tsc2007 chip not only has a resistive touch screen controller but
>> also an external AUX adc imput which can be used for an ambient
>> light sensor, battery voltage monitoring or any general purpose.
>> 
>> Additionally it can measure the chip temperature.
>> 
>> This extension provides an iio interface for these adc channels
>> in addition to the raw x, y, z values and the estimated touch
>> screen resistance. This can be used for debugging or special
>> applications.
> I'm unconvinced that exposing the touch related channels is terribly
> useful.

Mostly for debugging of if someone wants to do a (better) touch detection
in user space.

>  Fair enough on the aux channel and temperature though.
> 
> Otherwise a few minor bits and bobs.
> 
> Jonathan
>> 
>> Signed-off-by: H. Nikolaus Schaller <hns@xxxxxxxxxxxxx>
>> ---
>> drivers/input/touchscreen/Kconfig   |   1 +
>> drivers/input/touchscreen/tsc2007.c | 137 +++++++++++++++++++++++++++++++++++-
>> 2 files changed, 136 insertions(+), 2 deletions(-)
>> 
>> diff --git a/drivers/input/touchscreen/Kconfig b/drivers/input/touchscreen/Kconfig
>> index 2fb1f43..84c28e8 100644
>> --- a/drivers/input/touchscreen/Kconfig
>> +++ b/drivers/input/touchscreen/Kconfig
>> @@ -1019,6 +1019,7 @@ config TOUCHSCREEN_TSC2005
>> config TOUCHSCREEN_TSC2007
>> 	tristate "TSC2007 based touchscreens"
>> 	depends on I2C
>> +	select IIO
> This is pulling quite a bit of core IIO code in for a feature a lot
> of users of this chip won't care about...

Ah, yes.

We didn't notice because we use many other IIO devices on the same board (GTA04).

So I will add some #ifdef CONFIG_IIO where necessary.


>> 	help
>> 	  Say Y here if you have a TSC2007 based touchscreen.
>> 
>> diff --git a/drivers/input/touchscreen/tsc2007.c b/drivers/input/touchscreen/tsc2007.c
>> index e9d5086..559cbc6 100644
>> --- a/drivers/input/touchscreen/tsc2007.c
>> +++ b/drivers/input/touchscreen/tsc2007.c
>> @@ -30,6 +30,9 @@
>> #include <linux/of.h>
>> #include <linux/of_gpio.h>
>> #include <linux/input/touchscreen.h>
>> +#include <linux/iio/iio.h>
>> +#include <linux/iio/machine.h>
> Why machine.h? (or driver.h for that reason).

Good question. Header files sometimes get in during
development and are forgotten to take out... Or had
been necessary when development started a while ago.
Indeed I don't know why they are there.

> 
>> +#include <linux/iio/driver.h>

I have checked and we really neither need machine.h nor driver.h.

>> 
>> #define TSC2007_MEASURE_TEMP0		(0x0 << 4)
>> #define TSC2007_MEASURE_AUX		(0x2 << 4)
>> @@ -61,6 +64,16 @@
>> #define READ_X		(ADC_ON_12BIT | TSC2007_MEASURE_X)
>> #define PWRDOWN		(TSC2007_12BIT | TSC2007_POWER_OFF_IRQ_EN)
>> 
>> +#define TSC2007_CHAN_IIO(_chan, _name, _type, _chan_info) \
>> +{ \
>> +	.datasheet_name = _name, \
>> +	.type = _type, \
>> +	.info_mask_separate = BIT(IIO_CHAN_INFO_RAW) |	\
>> +			BIT(_chan_info), \
>> +	.indexed = 1, \
>> +	.channel = _chan, \
>> +}
>> +
>> struct ts_event {
>> 	u16	x;
>> 	u16	y;
>> @@ -69,9 +82,11 @@ struct ts_event {
>> 
>> struct tsc2007 {
>> 	struct input_dev	*input;
>> +	struct iio_dev		*indio;
>> 	char			phys[32];
>> 
>> 	struct i2c_client	*client;
>> +	struct mutex		mlock;
>> 
>> 	u16			model;
>> 	u16			x_plate_ohms;
>> @@ -192,7 +207,10 @@ static irqreturn_t tsc2007_soft_irq(int irq, void *handle)
>> 	while (!ts->stopped && tsc2007_is_pen_down(ts)) {
>> 
>> 		/* pen is down, continue with the measurement */
>> +
>> +		mutex_lock(&ts->mlock);
>> 		tsc2007_read_values(ts, &tc);
>> +		mutex_unlock(&ts->mlock);
>> 
>> 		rt = tsc2007_calculate_resistance(ts, &tc);
>> 
>> @@ -319,6 +337,86 @@ static void tsc2007_close(struct input_dev *input_dev)
>> 	tsc2007_stop(ts);
>> }
>> 
>> +static const struct iio_chan_spec tsc2007_iio_channel[] = {
>> +	TSC2007_CHAN_IIO(0, "x", IIO_VOLTAGE, IIO_CHAN_INFO_RAW),
>> +	TSC2007_CHAN_IIO(1, "y", IIO_VOLTAGE, IIO_CHAN_INFO_RAW),
>> +	TSC2007_CHAN_IIO(2, "z1", IIO_VOLTAGE, IIO_CHAN_INFO_RAW),
>> +	TSC2007_CHAN_IIO(3, "z2", IIO_VOLTAGE, IIO_CHAN_INFO_RAW),
>> +	TSC2007_CHAN_IIO(4, "adc", IIO_VOLTAGE, IIO_CHAN_INFO_RAW),
>> +	TSC2007_CHAN_IIO(5, "rt", IIO_VOLTAGE, IIO_CHAN_INFO_RAW), /* Ohms? */
> This one needs some explanation.  What is it measuring?

Well, it is reporting the raw conductivity of the touch under certain
conditions. But basically it is also a voltage measured by the ADC.

The real pressure value reported to user space is calculated
using this and the z1 and z2 values.

If not pressed, conductivity is 0 and if lightly touched it jumps
to some base value. When more pressed, conductivity increases
while resistance goes down to some 300 Ohms or so.

But I have not found an IIO_OHM or IIO_MHO constant. Which would also
not be the best description because it is not scaled to real ohms.

> 
>> +	TSC2007_CHAN_IIO(6, "pen", IIO_PRESSURE, IIO_CHAN_INFO_RAW),
> At the moment this is defined as barometric pressure.

Ok, I see.

>  I suppose there
> is no reason it can't extend to touch pressure though, even if it's a boolean
> like this...

So let's keep it this way?

> 
>> +	TSC2007_CHAN_IIO(7, "temp0", IIO_TEMP, IIO_CHAN_INFO_RAW),
>> +	TSC2007_CHAN_IIO(8, "temp1", IIO_TEMP, IIO_CHAN_INFO_RAW),
> I would be tempted to only expose those channels that have a meaning
> outside of touch screen usage (e.g. adc, temp0 and temp1).  

Well, for debugging and checking for non-responding or defective touch
it is very handy to have them in /sys/bus/iio for direct inspection.
For example we run a device test tool reading such values.

You might argue that we should run our own fork for this purpose to provide
a patched driver. But we want people to use the kernel from kernel.org
and still be able to do such debugging without asking them to replace the
kernel first.

>> +};
>> +
>> +static int tsc2007_read_raw(struct iio_dev *indio_dev,
>> +	struct iio_chan_spec const *chan, int *val, int *val2, long mask)
>> +{
>> +	struct  tsc2007 *tsc = iio_priv(indio_dev);
>> +	int adc_chan = chan->channel;
>> +	int ret = 0;
>> +
>> +	if (adc_chan >= ARRAY_SIZE(tsc2007_iio_channel))
>> +		return -EINVAL;
>> +
>> +	if (mask != IIO_CHAN_INFO_RAW)
>> +		return -EINVAL;
>> +
>> +	mutex_lock(&tsc->mlock);
>> +
>> +	switch (chan->channel) {
>> +	case 0:
>> +		*val = tsc2007_xfer(tsc, READ_X);
>> +		break;
>> +	case 1:
>> +		*val = tsc2007_xfer(tsc, READ_Y);
>> +		break;
>> +	case 2:
>> +		*val = tsc2007_xfer(tsc, READ_Z1);
>> +		break;
>> +	case 3:
>> +		*val = tsc2007_xfer(tsc, READ_Z2);
>> +		break;
>> +	case 4:
>> +		*val = tsc2007_xfer(tsc, (ADC_ON_12BIT | TSC2007_MEASURE_AUX));
>> +		break;
>> +	case 5: {
>> +		struct ts_event tc;
>> +
>> +		tc.x = tsc2007_xfer(tsc, READ_X);
>> +		tc.z1 = tsc2007_xfer(tsc, READ_Z1);
>> +		tc.z2 = tsc2007_xfer(tsc, READ_Z2);
>> +		*val = tsc2007_calculate_resistance(tsc, &tc);
>> +		break;
>> +	}
>> +	case 6:
>> +		*val = tsc2007_is_pen_down(tsc);
>> +		break;
>> +	case 7:
>> +		*val = tsc2007_xfer(tsc,
>> +				    (ADC_ON_12BIT | TSC2007_MEASURE_TEMP0));
>> +		break;
>> +	case 8:
>> +		*val = tsc2007_xfer(tsc,
>> +				    (ADC_ON_12BIT | TSC2007_MEASURE_TEMP1));
>> +		break;
>> +	}
>> +
>> +	/* Prepare for next touch reading - power down ADC, enable PENIRQ */
>> +	tsc2007_xfer(tsc, PWRDOWN);
>> +
>> +	mutex_unlock(&tsc->mlock);
>> +
>> +	ret = IIO_VAL_INT;
>> +
>> +	return ret;
>> +}
>> +
>> +static const struct iio_info tsc2007_iio_info = {
>> +	.read_raw = tsc2007_read_raw,
>> +	.driver_module = THIS_MODULE,
>> +};
>> +
>> #ifdef CONFIG_OF
>> static int tsc2007_get_pendown_state_gpio(struct device *dev)
>> {
>> @@ -453,15 +551,20 @@ static int tsc2007_probe(struct i2c_client *client,
>> 	const struct tsc2007_platform_data *pdata = dev_get_platdata(&client->dev);
>> 	struct tsc2007 *ts;
>> 	struct input_dev *input_dev;
>> +	struct iio_dev *indio_dev;
>> 	int err;
>> 
>> 	if (!i2c_check_functionality(client->adapter,
>> 				     I2C_FUNC_SMBUS_READ_WORD_DATA))
>> 		return -EIO;
>> 
>> -	ts = devm_kzalloc(&client->dev, sizeof(struct tsc2007), GFP_KERNEL);
>> -	if (!ts)
>> +	indio_dev = devm_iio_device_alloc(&client->dev, sizeof(*ts));
>> +	if (!indio_dev) {
>> +		dev_err(&client->dev, "iio_device_alloc failed\n");
>> 		return -ENOMEM;
>> +	}
>> +
>> +	ts = iio_priv(indio_dev);
>> 
>> 	input_dev = devm_input_allocate_device(&client->dev);
>> 	if (!input_dev)
>> @@ -469,10 +572,26 @@ static int tsc2007_probe(struct i2c_client *client,
>> 
>> 	i2c_set_clientdata(client, ts);
>> 
>> +	indio_dev->name = "tsc2007";
>> +	indio_dev->dev.parent = &client->dev;
>> +	indio_dev->info = &tsc2007_iio_info;
>> +	indio_dev->modes = INDIO_DIRECT_MODE;
>> +	indio_dev->channels = tsc2007_iio_channel;
>> +	indio_dev->num_channels = ARRAY_SIZE(tsc2007_iio_channel);
>> +
>> +	err = iio_device_register(indio_dev);
>> +	if (err < 0) {
>> +		dev_err(&client->dev, "iio_device_register() failed: %d\n",
>> +			err);
>> +		return err;
>> +	}
>> +
>> 	ts->client = client;
>> 	ts->irq = client->irq;
>> 	ts->input = input_dev;
>> +	ts->indio = indio_dev;
>> 	init_waitqueue_head(&ts->wait);
>> +	mutex_init(&ts->mlock);
>> 
>> 	snprintf(ts->phys, sizeof(ts->phys),
>> 		 "%s/input0", dev_name(&client->dev));
>> @@ -548,6 +667,19 @@ static int tsc2007_probe(struct i2c_client *client,
>> 	return 0;
>> }
>> 
>> +static int tsc2007_remove(struct i2c_client *client)
>> +{
>> +	struct tsc2007 *ts = i2c_get_clientdata(client);
>> +	struct input_dev *input_dev = ts->input;
>> +	struct iio_dev *indio_dev = ts->indio;
>> +
>> +	input_unregister_device(input_dev);
>> +
>> +	iio_device_unregister(indio_dev);
>> +
>> +	return 0;
>> +}
>> +
>> static const struct i2c_device_id tsc2007_idtable[] = {
>> 	{ "tsc2007", 0 },
>> 	{ }
>> @@ -570,6 +702,7 @@ static struct i2c_driver tsc2007_driver = {
>> 	},
>> 	.id_table	= tsc2007_idtable,
>> 	.probe		= tsc2007_probe,
>> +	.remove		= tsc2007_remove,
>> };
>> 
>> module_i2c_driver(tsc2007_driver);
>> 
> 

BR and thanks,
Nikolaus