[PATCH v3 08/11] input: touchscreen: resistive-adc-touch: add generic resistive ADC touchscreen
Dmitry Torokhov
dmitry.torokhov at gmail.com
Mon Apr 23 16:22:51 PDT 2018
Hi Eugen,
On Tue, Apr 10, 2018 at 11:57:54AM +0300, Eugen Hristev 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 at microchip.com>
> ---
> Changes in v3:
> - pressure now reported naturally growing down-up
> - using helpers from touchscreen.h to parse DT properties
> - added devm_add_action_or_reset to handle callback buffer clean on exit
> - changed compatible and threshold property to adapt to changed bindings
>
> 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/resistive-adc-touch.c | 200 ++++++++++++++++++++++++
> 3 files changed, 214 insertions(+)
> create mode 100644 drivers/input/touchscreen/resistive-adc-touch.c
>
> diff --git a/drivers/input/touchscreen/Kconfig b/drivers/input/touchscreen/Kconfig
> index 4f15496..8f85d3a 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 resistive-adc-touch.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..843c7f9 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-$(CONFIG_TOUCHSCREEN_ADC) += resistive-adc-touch.o
> obj-$(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/resistive-adc-touch.c b/drivers/input/touchscreen/resistive-adc-touch.c
> new file mode 100644
> index 0000000..7e201ee
> --- /dev/null
> +++ b/drivers/input/touchscreen/resistive-adc-touch.c
> @@ -0,0 +1,200 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/*
> + * ADC generic resistive touchscreen (GRTS)
> + *
> + * Copyright (C) 2017,2018 Microchip Technology,
> + * Author: Eugen Hristev <eugen.hristev at microchip.com>
> + *
> + */
> +#include <linux/input.h>
> +#include <linux/input/touchscreen.h>
> +#include <linux/iio/consumer.h>
> +#include <linux/iio/iio.h>
> +#include <linux/module.h>
> +#include <linux/of.h>
> +#include <linux/of_device.h>
> +#include <linux/platform_device.h>
> +
> +#define DRIVER_NAME "resistive-adc-touch"
> +#define GRTS_DEFAULT_PRESSURE_THRESHOLD 50000
> +#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
> + * @prop: touchscreen properties struct
> + */
> +struct grts_state {
> + u32 pressure_threshold;
> + bool pressure;
> + struct iio_channel *iio_chans;
> + struct iio_cb_buffer *iio_cb;
> + struct input_dev *input;
> + struct touchscreen_properties prop;
> +};
> +
> +static int grts_cb(const void *data, void *private)
> +{
> + const u16 *touch_info = data;
> + struct grts_state *st = private;
> +
Extra blank line.
> + unsigned int x, y, press = 0xFFFF;
Why to you need to initialize "press"?
> +
> + /* 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))) {
> + /* report end of touch */
Hm, so this makes "press" not pressure but resistance...
> + input_report_key(st->input, BTN_TOUCH, 0);
> + input_sync(st->input);
> + return 0;
> + }
> +
> + /* report proper touch to subsystem*/
> + touchscreen_report_pos(st->input, &st->prop, x, y, false);
> + if (st->pressure)
> + input_report_abs(st->input, ABS_PRESSURE, press);
and if this is resistance, then you want to have:
input_report_abs(st->input, ABS_PRESSURE,
st->resistance_threshold - resistance);
> + input_report_key(st->input, BTN_TOUCH, 1);
> + input_sync(st->input);
> +
> + return 0;
> +}
> +
> +static int grts_open(struct input_dev *dev)
> +{
> + int error;
> + struct grts_state *st = input_get_drvdata(dev);
> +
> + error = iio_channel_start_all_cb(st->iio_cb);
> + if (error) {
> + dev_err(dev->dev.parent, "failed to start callback buffer.\n");
> + return 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 void grts_disable(void *data)
> +{
> + iio_channel_release_all_cb(data);
> +}
> +
> +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;
Let's call this variable "error". There is also no need to initialize it
to 0.
> +
> + st = devm_kzalloc(dev, sizeof(struct grts_state), GFP_KERNEL);
> + if (!st)
> + return -ENOMEM;
> +
> + ret = of_property_read_u32(node, "touchscreen-threshold-pressure",
> + &st->pressure_threshold);
Let's use generic device property API (device_property_read_u32).
> + if (ret < 0) {
I do not think of_ or device_ property API returns positive on success.
So simply
if (error) {
...
}
> + 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);
> +
Extra blank line.
> + 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->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);
I am sure we can figure the range given the resistance threshold.
> +
> + input->evbit[0] = BIT_MASK(EV_KEY) | BIT_MASK(EV_ABS);
> + input->keybit[BIT_WORD(BTN_TOUCH)] = BIT_MASK(BTN_TOUCH);
Replace this 2 with
input_set_capability(input, EV_KEY, BTN_TOUCH);
> +
> + /* parse optional device tree properties */
> + touchscreen_parse_properties(input, false, &st->prop);
> +
> + 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(dev, grts_cb, st);
> +
> + if (IS_ERR(st->iio_cb)) {
> + dev_err(dev, "failed to allocate callback buffer.\n");
> + ret = PTR_ERR(st->iio_cb);
> + return ret;
> + }
> +
> + ret = devm_add_action_or_reset(dev, grts_disable, st->iio_cb);
if (error)
return error;
> +
> + platform_set_drvdata(pdev, st);
I do not think you are using platform device driver data anywhere.
> +
> + return ret;
Prefer explicit success returns, so
return 0;
> +}
> +
> +static const struct of_device_id grts_of_match[] = {
> + {
> + .compatible = "resistive-adc-touch",
> + }, {
> + /* sentinel */
> + },
> +};
> +
> +MODULE_DEVICE_TABLE(of, grts_of_match);
> +
> +static struct platform_driver grts_driver = {
> + .probe = grts_probe,
> + .driver = {
> + .name = DRIVER_NAME,
Keep indenting with tabs please.
> + .of_match_table = of_match_ptr(grts_of_match),
> + },
> +};
> +
> +module_platform_driver(grts_driver);
> +
> +MODULE_AUTHOR("Eugen Hristev <eugen.hristev at microchip.com>");
> +MODULE_DESCRIPTION("Generic ADC Resistive Touch Driver");
> +MODULE_LICENSE("GPL v2");
> --
> 2.7.4
>
--
Dmitry
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