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SubjectRe: [PATCH v2 07/10] input: touchscreen: touch_adc: add generic resistive ADC touchscreen
On Fri, Mar 30, 2018 at 01:58:35PM +0100, Jonathan Cameron wrote:
> On Tue, 27 Mar 2018 15:32:40 +0300
> Eugen Hristev <eugen.hristev@microchip.com> wrote:
>
> > This adds a generic resistive touchscreen (GRTS) driver, which is based
> > on an IIO device (an ADC). It must be connected to the channels of an ADC
> > to receive touch data. Then it will feed the data into the input subsystem
> > where it registers an input device.
> > It uses an IIO callback buffer to register to the IIO device
> >
> > Some parts of this patch are based on initial original work by
> > Mohamed Jamsheeth Hajanajubudeen and Bandaru Venkateswara Swamy
> >
> > Signed-off-by: Eugen Hristev <eugen.hristev@microchip.com>
> I like this a lot!
>
> A few minor bits and bobs inline. Over to Dmitry for the input
> side of things.
>
> Jonathan
>
> > ---
> > Changes in v2:
> > - this is now a generic resistive adc touchscreen driver
> >
> > drivers/input/touchscreen/Kconfig | 13 +++
> > drivers/input/touchscreen/Makefile | 1 +
> > drivers/input/touchscreen/touch_adc.c | 199 ++++++++++++++++++++++++++++++++++
> > 3 files changed, 213 insertions(+)
> > create mode 100644 drivers/input/touchscreen/touch_adc.c
> >
> > diff --git a/drivers/input/touchscreen/Kconfig b/drivers/input/touchscreen/Kconfig
> > index 4f15496..afd879f 100644
> > --- a/drivers/input/touchscreen/Kconfig
> > +++ b/drivers/input/touchscreen/Kconfig
> > @@ -92,6 +92,19 @@ config TOUCHSCREEN_AD7879_SPI
> > To compile this driver as a module, choose M here: the
> > module will be called ad7879-spi.
> >
> > +config TOUCHSCREEN_ADC
> > + tristate "Generic ADC based resistive touchscreen"
> > + depends on IIO
> > + select IIO_BUFFER_CB
> > + help
> > + Say Y here if you want to use the generic ADC
> > + resistive touchscreen driver.
> > +
> > + If unsure, say N (but it's safe to say "Y").
> > +
> > + To compile this driver as a module, choose M here: the
> > + module will be called touch_adc.ko.
> > +
> > config TOUCHSCREEN_AR1021_I2C
> > tristate "Microchip AR1020/1021 i2c touchscreen"
> > depends on I2C && OF
> > diff --git a/drivers/input/touchscreen/Makefile b/drivers/input/touchscreen/Makefile
> > index dddae79..cbe6121 100644
> > --- a/drivers/input/touchscreen/Makefile
> > +++ b/drivers/input/touchscreen/Makefile
> > @@ -13,6 +13,7 @@ obj-$(CONFIG_TOUCHSCREEN_AD7877) += ad7877.o
> > obj-$(CONFIG_TOUCHSCREEN_AD7879) += ad7879.o
> > obj-$(CONFIG_TOUCHSCREEN_AD7879_I2C) += ad7879-i2c.o
> > obj-$(CONFIG_TOUCHSCREEN_AD7879_SPI) += ad7879-spi.o
> > +obj-$(CONFIG_TOUCHSCREEN_ADC) += touch_adc.o
> > obj-$(CONFIG_TOUCHSCREEN_ADS7846) += ads7846.o
> > obj-$(CONFIG_TOUCHSCREEN_AR1021_I2C) += ar1021_i2c.o
> > obj-$(CONFIG_TOUCHSCREEN_ATMEL_MXT) += atmel_mxt_ts.o
> > diff --git a/drivers/input/touchscreen/touch_adc.c b/drivers/input/touchscreen/touch_adc.c
> > new file mode 100644
> > index 0000000..de4b929
> > --- /dev/null
> > +++ b/drivers/input/touchscreen/touch_adc.c
> > @@ -0,0 +1,199 @@
> > +// SPDX-License-Identifier: GPL-2.0
> > +/*
> > + * ADC generic resistive touchscreen (GRTS)
> > + *
> > + * Copyright (C) 2017,2018 Microchip Technology,
> > + * Author: Eugen Hristev <eugen.hristev@microchip.com>
> > + *
> > + */
> > +#include <linux/input.h>
> > +#include <linux/of.h>
> > +#include <linux/of_device.h>
> > +#include <linux/platform_device.h>
> > +#include <linux/iio/consumer.h>
> > +#include <linux/iio/iio.h>
> > +#include <linux/module.h>
> > +
> > +#define DRIVER_NAME "touch_adc"
> > +#define GRTS_DEFAULT_PRESSURE_THRESHOLD 10000
> > +#define MAX_POS_MASK GENMASK(11, 0)
> > +
> > +/**
> > + * grts_state - generic resistive touch screen information struct
> > + * @pressure_threshold: number representing the threshold for the pressure
> > + * @pressure: are we getting pressure info or not
> > + * @iio_chans: list of channels acquired
> > + * @iio_cb: iio_callback buffer for the data
> > + * @input: the input device structure that we register
> > + */
> > +struct grts_state {
> > + u32 pressure_threshold;
> > + bool pressure;
> > + struct iio_channel *iio_chans;
> > + struct iio_cb_buffer *iio_cb;
> > + struct input_dev *input;
> > +};
> > +
> > +static int grts_cb(const void *data, void *private)
> > +{
> > + const u16 *touch_info = data;
> > + struct grts_state *st = private;
> > +
> > + unsigned int x, y, press = 0xFFFF;
> > +
> > + /* channel data coming in buffer in the order below */
> > + x = touch_info[0];
> > + y = touch_info[1];
> > + if (st->pressure)
> > + press = touch_info[2];
> > +
> > + if ((!x && !y) || (st->pressure && (press > st->pressure_threshold))) {
> Ah, clearly pressure is the other way around to I assumed and gets larger as
> the pressure is reduced. hmm.

OK, in this case it should not be reported directly as ABS_PRESSURE, as
ABSP_RESSURE value is expected to grow the firmer the finger touches the
surface, and reduce to 0 when finger is about to be lifted.

>
> > + /* report end of touch */
> > + input_report_key(st->input, BTN_TOUCH, 0);
> > + input_sync(st->input);
> > + return 0;
> > + }
> > +
> > + /* report proper touch to subsystem*/
> > + input_report_abs(st->input, ABS_X, x);
> > + input_report_abs(st->input, ABS_Y, y);
> > + if (st->pressure)
> > + input_report_abs(st->input, ABS_PRESSURE, press);
> > + input_report_key(st->input, BTN_TOUCH, 1);
> > + input_sync(st->input);
> blank line preferred here.
>
> > + return 0;
> > +}
> > +
> > +static int grts_open(struct input_dev *dev)
> > +{
> > + int ret;
> > + struct grts_state *st = input_get_drvdata(dev);
> > +
> > + ret = iio_channel_start_all_cb(st->iio_cb);
> > + if (ret) {
> > + dev_err(dev->dev.parent, "failed to start callback buffer.\n");
> > + return ret;
> Drop the return ret out of the brackets.

Actually I prefer explicit "success" return path. But I would
appreciate if we called this "ret" variable "error".

>
> > + }
> > + return 0;
> > +}
> > +
> > +static void grts_close(struct input_dev *dev)
> > +{
> > + struct grts_state *st = input_get_drvdata(dev);
> > +
> > + iio_channel_stop_all_cb(st->iio_cb);
> > +}
> > +
> > +static int grts_probe(struct platform_device *pdev)
> > +{
> > + struct grts_state *st;
> > + struct input_dev *input;
> > + struct device *dev = &pdev->dev;
> > + struct device_node *node = dev->of_node;
> > + struct iio_channel *chan;
> > + int ret = 0;
> > +
> > + st = devm_kzalloc(dev, sizeof(struct grts_state), GFP_KERNEL);
> > + if (!st)
> > + return -ENOMEM;
> > +
> > + ret = of_property_read_u32(node,
> > + "generic-adc-resistive-touchscreen,pressure-threshold",
> > + &st->pressure_threshold);
> > + if (ret < 0) {
> > + dev_dbg(dev, "can't get touchscreen pressure threshold property.\n");
> > + st->pressure_threshold = GRTS_DEFAULT_PRESSURE_THRESHOLD;
> > + }
> > +
> > + /* get the channels from IIO device */
> > + st->iio_chans = devm_iio_channel_get_all(dev);
> > +
> > + if (IS_ERR(st->iio_chans)) {
> > + if (PTR_ERR(st->iio_chans) != -EPROBE_DEFER)
> > + dev_err(dev, "can't get iio channels.\n");
> > + return PTR_ERR(st->iio_chans);
> > + }
> > +
> > + chan = &st->iio_chans[0];
> > + st->pressure = false;
> > + while (chan && chan->indio_dev) {
> > + if (!strcmp(chan->channel->datasheet_name, "pressure"))
> > + st->pressure = true;
> > + chan++;
> > + }
> > +
> > + input = devm_input_allocate_device(dev);
> > + if (!input) {
> > + dev_err(dev, "failed to allocate input device.\n");
> > + return -ENOMEM;
> > + }
> > +
> > + input->name = DRIVER_NAME;
> > + input->id.bustype = BUS_HOST;
> > + input->dev.parent = dev;

This is already being set by devm_input_allocate_device().

> > + input->open = grts_open;
> > + input->close = grts_close;
> > +
> > + input_set_abs_params(input, ABS_X, 0, MAX_POS_MASK - 1, 0, 0);
> > + input_set_abs_params(input, ABS_Y, 0, MAX_POS_MASK - 1, 0, 0);
> > + if (st->pressure)
> > + input_set_abs_params(input, ABS_PRESSURE, 0, 0xffffff, 0, 0);

It would be good if you used the API from
include/linux/input/touchscreen.h to parse standard touchscreen
properties and implement sizing, flippign and rotation of the screen.

> > +
> > + input->evbit[0] = BIT_MASK(EV_KEY) | BIT_MASK(EV_ABS);
> > + input->keybit[BIT_WORD(BTN_TOUCH)] = BIT_MASK(BTN_TOUCH);
> > +
> > + st->input = input;
> > + input_set_drvdata(input, st);
> > +
> > + ret = input_register_device(input);
> > + if (ret) {
> > + dev_err(dev, "failed to register input device.");
> > + return ret;
> > + }
> > +
> > + st->iio_cb = iio_channel_get_all_cb(&pdev->dev, grts_cb, st);

Hmm, we don't have devm-variant for this? Then you could use
devm_add_action_or_reset() to add cleanup action and completely remove
grts_remove().

> > +
> > + if (IS_ERR(st->iio_cb)) {
> > + dev_err(dev, "failed to allocate callback buffer.\n");
> > + ret = PTR_ERR(st->iio_cb);
> > + return ret;
> > + }
> > +
> > + platform_set_drvdata(pdev, st);
> > +
> > + return ret;
> > +}
> > +
> > +static int grts_remove(struct platform_device *pdev)
> > +{
> > + struct grts_state *st = platform_get_drvdata(pdev);
> > +
> > + iio_channel_release_all_cb(st->iio_cb);
> > + input_unregister_device(st->input);

This call is not needed since you are using managed input device.

> blank line preferred before simple returns.
>
> > + return 0;
> > +}
> > +
> > +static const struct of_device_id grts_of_match[] = {
> > + {
> > + .compatible = "generic-resistive-adc-touch",
> > + }, {
> > + /* sentinel */
> > + },
> > +};
> > +
> > +MODULE_DEVICE_TABLE(of, grts_of_match);
> > +
> > +static struct platform_driver grts_driver = {
> > + .probe = grts_probe,
> > + .remove = grts_remove,
> > + .driver = {
> > + .name = DRIVER_NAME,
> > + .of_match_table = of_match_ptr(grts_of_match),
> > + },
> > +};
> > +
> > +module_platform_driver(grts_driver);
> > +
> > +MODULE_AUTHOR("Eugen Hristev <eugen.hristev@microchip.com>");
> > +MODULE_DESCRIPTION("Generic ADC Resistive Touch Driver");
> > +MODULE_LICENSE("GPL v2");
>

Thanks.

--
Dmitry

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