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Subject: Re: [PATCH v6 6/9] input: touchscreen: resistive-adc-touch: add
 generic resistive ADC touchscreen
To:     Dmitry Torokhov <dmitry.torokhov@gmail.com>
CC:     <jic23@kernel.org>, <ludovic.desroches@microchip.com>,
        <alexandre.belloni@bootlin.com>,
        <linux-arm-kernel@lists.infradead.org>,
        <devicetree@vger.kernel.org>, <linux-kernel@vger.kernel.org>,
        <linux-iio@vger.kernel.org>, <linux-input@vger.kernel.org>,
        <nicolas.ferre@microchip.com>, <robh@kernel.org>
References: <1526898477-9952-1-git-send-email-eugen.hristev@microchip.com>
 <1526898477-9952-7-git-send-email-eugen.hristev@microchip.com>
 <20180521210611.GB74396@dtor-ws>
From:   Eugen Hristev <eugen.hristev@microchip.com>
Message-ID: <56a46a3e-07da-552a-d621-0088615f33d0@microchip.com>
Date:   Tue, 22 May 2018 10:56:09 +0300
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On 22.05.2018 00:06, Dmitry Torokhov wrote:
> On Mon, May 21, 2018 at 01:27:54PM +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@microchip.com>
> 
> Acked-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>
> 
> I assume this will go through IIO tree? Just a couple of comsmetic
> comments below, feel free to ignore.

Thank you, I modified as you suggested and sent out v7. Jonathan said in 
an earlier e-mail that he will take them through IIO tree. Waiting on 
his feedback.

Eugen
> 
>> ---
>> Changes in v6:
>>   -  changed a dev_err to dev_dbg which was forgotten in v5.
>>
>> Changes in v5:
>>   - return error on probe if failed add_action_or_reset
>>   - renamed property touchscreen-threshold-pressure to
>> touchscreen-min-pressure, changed variables accordingly
>>
>> Changes in v4:
>>   - added a small description in file header
>>   - changed MAX_POS_MASK to GRTS_MAX_POS_MASK
>>   - initialized press with 0, as this value means no touch.
>> press has to be initialized because compiler/checkpatch complains
>> that can be used uninitialized.
>>   - changed of_property_read_u32 to device_*
>>   - set_abs_params for pressure will have range according to threshold
>>   - changed evbit and keybit with set_capability call
>>   - changed variable names to error instead of ret
>>   - checked errors for add_action_or_reset
>>   - cosmetic cleaning
>>
>> 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 | 201 ++++++++++++++++++++++++
>>   3 files changed, 215 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..05d629b
>> --- /dev/null
>> +++ b/drivers/input/touchscreen/resistive-adc-touch.c
>> @@ -0,0 +1,201 @@
>> +// SPDX-License-Identifier: GPL-2.0
>> +/*
>> + * ADC generic resistive touchscreen (GRTS)
>> + * This is a generic input driver that connects to an ADC
>> + * given the channels in device tree, and reports events to the input
>> + * subsystem.
>> + *
>> + * Copyright (C) 2017,2018 Microchip Technology,
>> + * Author: Eugen Hristev <eugen.hristev@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_MIN			50000
>> +#define GRTS_MAX_POS_MASK				GENMASK(11, 0)
>> +
>> +/**
>> + * grts_state - generic resistive touch screen information struct
>> + * @pressure_min:	number representing the minimum 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_min;
>> +	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;
>> +	unsigned int x, y, press = 0x0;
>> +
>> +	/* 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_min))) {
>> +		/* report end of touch */
>> +		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);
>> +	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 iio_channel *chan;
>> +	int error;
>> +
>> +	st = devm_kzalloc(dev, sizeof(struct grts_state), GFP_KERNEL);
>> +	if (!st)
>> +		return -ENOMEM;
>> +
>> +	error = device_property_read_u32(dev, "touchscreen-min-pressure",
>> +					 &st->pressure_min);
>> +	if (error) {
>> +		dev_dbg(dev, "can't get touchscreen-min-pressure property.\n");
>> +		st->pressure_min = GRTS_DEFAULT_PRESSURE_MIN;
>> +	}
> 
> I do not think it makes sense to complain about missing property if
> there is no "pressure" channel. Probably move down?
> 
>> +
>> +	/* 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);
> 
> 		error = PTR_ERR(st->iio_chans);
> 		if (error != -EPROBE_DEFER)
> 			dev_err(dev, "can't get iio channels.\n");
> 		return error;
> 
>> +	}
>> +
>> +	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, GRTS_MAX_POS_MASK - 1, 0, 0);
>> +	input_set_abs_params(input, ABS_Y, 0, GRTS_MAX_POS_MASK - 1, 0, 0);
>> +	if (st->pressure)
>> +		input_set_abs_params(input, ABS_PRESSURE, st->pressure_min,
>> +				     0xffff, 0, 0);
>> +
>> +	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);
>> +
>> +	error = input_register_device(input);
>> +	if (error) {
>> +		dev_err(dev, "failed to register input device.");
>> +		return error;
>> +	}
>> +
>> +	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");
>> +		error =  PTR_ERR(st->iio_cb);
>> +		return error;
> 
> Simply:
> 
> 		return PTR_ERR(st->iio_cb);
> 
> since you opted out of printing error codes in error messages.
> 
>> +	}
>> +
>> +	error = devm_add_action_or_reset(dev, grts_disable, st->iio_cb);
>> +	if (error) {
>> +		dev_err(dev, "failed to add disable action.\n");
>> +		return error;
>> +	}
>> +
>> +	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,
>> +		.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");
>> -- 
>> 2.7.4
>>
> 
> Thanks.
>