Date:   Sun, 23 Oct 2016 11:57:00 +0200
From:   "H. Nikolaus Schaller" <hns@...delico.com>
To:     Jonathan Cameron <jic23@...nel.org>
Cc:     Dmitry Torokhov <dmitry.torokhov@...il.com>,
        Rob Herring <robh+dt@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Benoît Cousson <bcousson@...libre.com>,
        Tony Lindgren <tony@...mide.com>,
        Russell King <linux@...linux.org.uk>,
        Arnd Bergmann <arnd@...db.de>,
        Michael Welling <mwelling@...e.org>,
        Mika Penttilä <mika.penttila@...tfour.com>,
        Javier Martinez Canillas <javier@....samsung.com>,
        Igor Grinberg <grinberg@...pulab.co.il>,
        Sebastian Reichel <sre@...nel.org>,
        "Andrew F. Davis" <afd@...com>, Mark Brown <broonie@...nel.org>,
        linux-input@...r.kernel.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-omap@...r.kernel.org,
        letux-kernel@...nphoenux.org, linux-iio@...r.kernel.org,
        kernel@...a-handheld.com
Subject: Re: [PATCH v4 4/8] drivers:input:tsc2007: add iio interface to read external ADC input and temperature

Hi,

> Am 23.10.2016 um 11:24 schrieb Jonathan Cameron <jic23@...nel.org>:
> 
> On 22/10/16 21:46, H. Nikolaus Schaller wrote:
>> Hi Jonathan,
>> 
>>> Am 22.10.2016 um 20:33 schrieb Jonathan Cameron <jic23@...nel.org>:
>>> 
>>> On 17/10/16 14:57, 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.
>>>> 
>>>> Since it is not wasting much resources and is very straightforward,
>>>> we simply provide all other adc channels as optional iio interfaces
>>>> as weel. This can be used for debugging or special applications.
>>> well
>>>> 
>>>> Signed-off-by: H. Nikolaus Schaller <hns@...delico.com>
>>> This could be cleaner done perhaps by factoring out the IIO stuff into a separate
>>> file and using a header with stubs to deal with the no available case.
>>> 
>>> There will only be a handful of stubs and it'll give you a lot cleaner code
>>> in here.
>>> 
>>> If def fun in .c files is always harder to deal with than in a header
>>> where stubs are really obvious.
>> 
>> Yes, it became a lot of #ifdefs spread over the source file.
>> 
>> The easiest thing would be to require IIO to be enabled :)
>> 
>> With your proposal to consider refactoring, I think the crucial part
>> is the conditional allocation either through devm_iio_device_alloc()
>> or devm_kzalloc(). This can be refactored into some conditional
>> tsc2007_alloc().
>> 
>> I have tried some draft (not tested and not tidied up) to check if the
>> direction is good.
>> 
>> This reduces the number of #ifdef CONFIG_IIO from 7 to 2 without introducing
>> new files or includes. There are also 2 other #ifdef CONFIG_OF so it doesn't
>> seem to be very complex now in comparison. And the patch itself has only a
>> handful of hunks (8).
>> 
>> Moving tsc2007_alloc into a separate file tsc2007_iio.c would only move around
>> one #ifdef CONFIG_OF from tsc2007.c but IMHO makes it more difficult to understand
>> because it is not really iio specific and one has to switch between two source
>> files. And I would have to touch the Makefile as well.
>> 
>> What do you think?
> I'd still split it.  The only bit of the IIO block that isn't specific is
> a tiny chunk of the allocation code (as you've highlighted).
> 
> Even that can be avoided by adding a tiny bit more indirection than would
> otherwise be needed (it's not pretty but it would give a clean separation).

I hope I understand what you mean (which is an indication that the result
may be much easier to read for you but not me...).

> It's pretty much the way this sort of optional functionality should always
> be done - means that if you don't care (i.e. it's not enabled) you don't
> even have to see the code.

> 
> Jonathan
>> 
>> If generally ok, I can include that in [PATCH v5].
>> 
>> BR and thanks,
>> Nikolaus
>> 
>> 
>> diff --git a/drivers/input/touchscreen/tsc2007.c b/drivers/input/touchscreen/tsc2007.c
>> index 5e3c4bf..691e79f 100644
>> --- a/drivers/input/touchscreen/tsc2007.c
>> +++ b/drivers/input/touchscreen/tsc2007.c
>> @@ -30,6 +30,7 @@
>> #include <linux/of.h>
>> #include <linux/of_gpio.h>
>> #include <linux/input/touchscreen.h>
>> +#include <linux/iio/iio.h>
>> 
>> #define TSC2007_MEASURE_TEMP0          (0x0 << 4)
>> #define TSC2007_MEASURE_AUX            (0x2 << 4)
>> @@ -69,9 +70,13 @@ struct ts_event {
>> 
>> struct tsc2007 {
>>        struct input_dev        *input;
>> +#ifdef CONFIG_IIO
>> +       struct iio_dev          *indio;
>> +#endif
> I wouldn't bother with this one.  Just have 
> struct iio_dev; before this and it'll waste a whole
> one pointer (+ you shouldn't need to have iio.h included
> in here once you have spit the files).

Looks as if I have to make a knot in my brain before I start to understand...

How can I use struct iio_dev here w/o including iio.h?

>>        char                    phys[32];
>> 
>>        struct i2c_client       *client;
>> +       struct mutex            mlock;
>> 
>>        u16                     model;
>>        u16                     x_plate_ohms;
>> @@ -192,7 +197,10 @@ 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 +327,162 @@ static void tsc2007_close(struct input_dev *input_dev)
>>        tsc2007_stop(ts);
>> }
>> 
>> +#ifdef CONFIG_IIO
>> +
>> +#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, \
>> +}
>> +
>> +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? */
>> +       TSC2007_CHAN_IIO(6, "pen", IIO_PRESSURE, IIO_CHAN_INFO_RAW),
>> +       TSC2007_CHAN_IIO(7, "temp0", IIO_TEMP, IIO_CHAN_INFO_RAW),
>> +       TSC2007_CHAN_IIO(8, "temp1", IIO_TEMP, IIO_CHAN_INFO_RAW),
>> +};
>> +
>> +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,
>> +};
>> +
>> +static int tsc2007_alloc(struct i2c_client *client, struct tsc2007 **ts,
>> +                          struct input_dev **input_dev)
>> +{
>> +       int err;
>> +       struct iio_dev *indio_dev;
>> +
>> +       indio_dev = devm_iio_device_alloc(&client->dev, sizeof(*ts));
> Instead of doing this to reduce the delta between versions make 
> iio_priv a struct tsc2007 **
> 
> That is have a single pointer in there and do your allocation of struct
> tsc2007 separately.

Sorry, but I think I do not completely understand what you mean here.

The problem is that we need to allocate some struct tsc2007 in both cases.
But in one case managed directly by &client->dev and in the other managed
indirectly. This is why I use the private area of struct iio_dev to store
the full struct tsc2007 and not just a pointer.

What I mean is:

>> +       indio_dev = devm_iio_device_alloc(&client->dev, sizeof(*ts));
>> 	*ts = iio_priv(indio_dev);

vs. 

>> 	 *ts = devm_kzalloc(&client->dev, sizeof(struct tsc2007), GFP_KERNEL);


So how can the IIO case just extend/wrap devm_kzalloc(&client->dev...) and still
be managed as well?

> 
> Having doing that, you can have this CONFIG_IIO block as just
> doing the iio stuff with the input elements pulled back into the main
> probe function.
> 
> Then define something like
> 
> iio_configure (stubbed to nothing if no IIO)
> and
> iio_unconfigure (also stubbed to nothing if no IIO).
> 
> A couple of additions in the header to make it all work
> (the struct tsc2007 and tsc2007_xfer() + a few of the
> register defines..
> 
> Nothing big and gets all the CONFIG_IIO into some really
> obvious stubbing out in the header.


Is there some example driver which is doing it that way to be optionally IIO
compatible? That might be easier to understand and copy than a description.

> 
>> +       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)
>> +               return -ENOMEM;
>> +
>> +       i2c_set_clientdata(client, *ts);
>> +       (*ts)->indio = indio_dev;
>> +
>> +       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;
>> +       }
>> +
>> +       return 0;
>> +}
>> +
>> +#define tsc2007_iio_device_unregister(ts) iio_device_unregister(ts->indio)
>> +
>> +#else /* CONFIG_IIO */
>> +
>> +static int tsc2007_alloc(struct i2c_client *client, struct tsc2007 **ts,
>> +                          struct input_dev **input_dev)
>> +{
>> +       int err;
>> +
>> +       *ts = devm_kzalloc(&client->dev, sizeof(struct tsc2007), GFP_KERNEL);
>> +       if (!*ts)
>> +               return -ENOMEM;
>> +
>> +       *input_dev = devm_input_allocate_device(&client->dev);
>> +       if (!*input_dev)
>> +               return -ENOMEM;
>> +
>> +       i2c_set_clientdata(client, *ts);
>> +
>> +       return 0;
>> +}
>> +
>> +#define tsc2007_iio_device_unregister(ts) /* not needed */
> That's rather ugly and fragile.  I'd stub it out as an actual function
> with no content and let the compiler drop it.

Well, it is a quick and dirty draft.
Should indeed better be a static (inline) function with empty body.

>> +
>> +#endif /* CONFIG_IIO */
>> +
>> #ifdef CONFIG_OF
>> static int tsc2007_get_pendown_state_gpio(struct device *dev)
>> {
>> @@ -459,20 +623,15 @@ static int tsc2007_probe(struct i2c_client *client,
>>                                     I2C_FUNC_SMBUS_READ_WORD_DATA))
>>                return -EIO;
>> 
>> -       ts = devm_kzalloc(&client->dev, sizeof(struct tsc2007), GFP_KERNEL);
>> -       if (!ts)
>> -               return -ENOMEM;
>> -
>> -       input_dev = devm_input_allocate_device(&client->dev);
>> -       if (!input_dev)
>> -               return -ENOMEM;
>> -
>> -       i2c_set_clientdata(client, ts);
>> +       err = tsc2007_alloc(client, &ts, &input_dev);
>> +       if (err < 0)
>> +               return err;
>> 
>>        ts->client = client;
>>        ts->irq = client->irq;
>>        ts->input = input_dev;
>>        init_waitqueue_head(&ts->wait);
>> +       mutex_init(&ts->mlock);
>> 
>>        snprintf(ts->phys, sizeof(ts->phys),
>>                 "%s/input0", dev_name(&client->dev));
>> @@ -543,6 +702,7 @@ static int tsc2007_probe(struct i2c_client *client,
>>        if (err < 0) {
>>                dev_err(&client->dev,
>>                        "Failed to setup chip: %d\n", err);
>> +               tsc2007_iio_device_unregister(ts);
>>                return err;     /* usually, chip does not respond */
>>        }
>> 
>> @@ -556,6 +716,14 @@ 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);
>> +       input_unregister_device(ts->input);
>> +       tsc2007_iio_device_unregister(ts);
>> +       return 0;
>> +}
>> +
>> static const struct i2c_device_id tsc2007_idtable[] = {
>>        { "tsc2007", 0 },
>>        { }
>> @@ -578,6 +746,7 @@ 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

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