Date:   Sun, 23 Oct 2016 10:24:21 +0100
From:   Jonathan Cameron <jic23@...nel.org>
To:     "H. Nikolaus Schaller" <hns@...delico.com>
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

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).

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).
>         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.

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.


> +       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.
> +
> +#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);
> 

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