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

H. Nikolaus Schaller
2016-09-24T17:07:22Z

Hi Jonathan,

> Am 24.09.2016 um 18:07 schrieb Jonathan Cameron <jic23@kernel.org>:
>
> 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@goldelico.com>
>> ---
>> 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