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

H. Nikolaus Schaller
2016-09-24T17:42:32Z

Hi Jonathan,

> Am 24.09.2016 um 19:26 schrieb Jonathan Cameron <jic23@kernel.org>:
>
> On 24/09/16 18:07, H. Nikolaus Schaller wrote:
>> 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.
> Not going to do anything at the rates you will get out of that interface.

Touch detection and processing does not need a fast interface. In standard
operation (input device) the tsc2007 is polled in multiples of jiffies.

And I don't know what people will do with it - in addition to debugging
and hardware testing which is what we are doing (and need in the upstream
driver - see below).

> I suspect this is a non starter. Lets see what Dmitry thinks.

Yes. More opinions are welcome.

>
> Jonathan
>>
>>> 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.
> Cool

I have already prepared for PATCH V4 and tested w/o CONFIG_IIO and with.

>>
>>
>>>> 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?
> Except I'm saying we should drop it entirely.
>>
>>>
>>>> + 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).
>>

The following is my main argument why we should not drop it (it also is
neither complex nor harmful if not used):

>> 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.

In other words: we do neither want to run our own kernel fork (which might not
be the standard case) but also not loose (practically required) features we
need...

>>
>>>> +};
>>>> +
>>>> +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

BR and thanks,
Nikolaus