Date:   Mon, 17 Oct 2022 13:19:29 +0900
From:   Dmitry Torokhov <dmitry.torokhov@...il.com>
To:     Job Noorman <job@...rman.info>
Cc:     Henrik Rydberg <rydberg@...math.org>, Luca Weiss <luca@...tu.xyz>,
        linux-kernel@...r.kernel.org, linux-input@...r.kernel.org
Subject: Re: [PATCH v3 2/3] Input: add driver for Himax hx83112b touchscreen
 devices

Hi Job,

On Sun, Oct 16, 2022 at 12:27:54PM +0200, Job Noorman wrote:
> This patch adds support for Himax hx83112b touchscreen devices. As there
> are no publicly available data sheets for these devices, the
> implementation is based on the driver of the downstream Android kernel
> used in the Fairphone 3. This patch is a complete rewrite, though, and
> the code bears no resemblence to the original implementation.
> 
> The driver has been tested on the aforementioned phone.
> 
> Signed-off-by: Job Noorman <job@...rman.info>
> ---
>  MAINTAINERS                                |   1 +
>  drivers/input/touchscreen/Kconfig          |  11 +
>  drivers/input/touchscreen/Makefile         |   1 +
>  drivers/input/touchscreen/himax_hx83112b.c | 382 +++++++++++++++++++++
>  4 files changed, 395 insertions(+)
>  create mode 100644 drivers/input/touchscreen/himax_hx83112b.c
> 
> diff --git a/MAINTAINERS b/MAINTAINERS
> index 2418bffe9187..51a03f9586f1 100644
> --- a/MAINTAINERS
> +++ b/MAINTAINERS
> @@ -9099,6 +9099,7 @@ M:	Job Noorman <job@...rman.info>
>  L:	linux-input@...r.kernel.org
>  S:	Maintained
>  F:	Documentation/devicetree/bindings/input/touchscreen/himax,hx83112b.yaml
> +F:	drivers/input/touchscreen/himax_hx83112b.c
>  
>  HIPPI
>  M:	Jes Sorensen <jes@...ined-monkey.org>
> diff --git a/drivers/input/touchscreen/Kconfig b/drivers/input/touchscreen/Kconfig
> index dc90a3ea51ee..113b7dd7da2f 100644
> --- a/drivers/input/touchscreen/Kconfig
> +++ b/drivers/input/touchscreen/Kconfig
> @@ -1379,4 +1379,15 @@ config TOUCHSCREEN_ZINITIX
>  	  To compile this driver as a module, choose M here: the
>  	  module will be called zinitix.
>  
> +config TOUCHSCREEN_HIMAX_HX83112B
> +	tristate "Himax hx83112b touchscreen driver"
> +	depends on REGMAP_I2C
> +	help
> +	  Say Y here to enable support for Himax hx83112b touchscreens.
> +
> +	  If unsure, say N.
> +
> +	  To compile this driver as a module, choose M here: the
> +	  module will be called himax_hx83112b.
> +
>  endif
> diff --git a/drivers/input/touchscreen/Makefile b/drivers/input/touchscreen/Makefile
> index 557f84fd2075..0f8bf79e01fe 100644
> --- a/drivers/input/touchscreen/Makefile
> +++ b/drivers/input/touchscreen/Makefile
> @@ -116,3 +116,4 @@ obj-$(CONFIG_TOUCHSCREEN_ROHM_BU21023)	+= rohm_bu21023.o
>  obj-$(CONFIG_TOUCHSCREEN_RASPBERRYPI_FW)	+= raspberrypi-ts.o
>  obj-$(CONFIG_TOUCHSCREEN_IQS5XX)	+= iqs5xx.o
>  obj-$(CONFIG_TOUCHSCREEN_ZINITIX)	+= zinitix.o
> +obj-$(CONFIG_TOUCHSCREEN_HIMAX_HX83112B)	+= himax_hx83112b.o
> diff --git a/drivers/input/touchscreen/himax_hx83112b.c b/drivers/input/touchscreen/himax_hx83112b.c
> new file mode 100644
> index 000000000000..d653e980fdaf
> --- /dev/null
> +++ b/drivers/input/touchscreen/himax_hx83112b.c
> @@ -0,0 +1,382 @@
> +// SPDX-License-Identifier: GPL-2.0-only
> +/*
> + * Driver for Himax hx83112b touchscreens
> + *
> + * Copyright (C) 2022 Job Noorman <job@...rman.info>
> + *
> + * This code is based on "Himax Android Driver Sample Code for QCT platform":
> + *
> + * Copyright (C) 2017 Himax Corporation.
> + */
> +
> +#include <linux/delay.h>
> +#include <linux/err.h>
> +#include <linux/gpio/consumer.h>
> +#include <linux/i2c.h>
> +#include <linux/input.h>
> +#include <linux/input/mt.h>
> +#include <linux/input/touchscreen.h>
> +#include <linux/interrupt.h>
> +#include <linux/kernel.h>
> +#include <linux/regmap.h>
> +
> +#define HIMAX_ID_83112B 0x83112b
> +
> +#define HIMAX_MAX_POINTS 10
> +
> +
> +#define HIMAX_REG_CFG_SET_ADDR	 0x00
> +#define HIMAX_REG_CFG_INIT_READ	 0x0c
> +#define HIMAX_REG_CFG_READ_VALUE 0x08
> +#define HIMAX_REG_READ_EVENT	 0x30
> +
> +#define HIMAX_CFG_PRODUCT_ID 0x900000d0
> +
> +#define HIMAX_INVALID_COORD 0xffff
> +
> +struct himax_event_point {
> +	__be16 x;
> +	__be16 y;
> +} __packed;
> +
> +struct himax_event {
> +	struct himax_event_point points[HIMAX_MAX_POINTS];
> +	u8 majors[HIMAX_MAX_POINTS];
> +	u8 pad0[2];
> +	u8 num_points;
> +	u8 pad1[2];
> +	u8 checksum_fix;
> +} __packed;
> +
> +static_assert(sizeof(struct himax_event) == 56);

Is this different from BUILD_BUG_ON()?

> +
> +struct himax_ts_data {
> +	struct gpio_desc *gpiod_rst;
> +	struct input_dev *input_dev;
> +	struct i2c_client *client;
> +	struct regmap *regmap;
> +	struct touchscreen_properties props;
> +};
> +
> +static const struct regmap_config himax_regmap_config = {
> +	.reg_bits = 8,
> +	.val_bits = 32,
> +	.val_format_endian = REGMAP_ENDIAN_LITTLE,
> +};
> +
> +static int himax_read_config(struct himax_ts_data *ts, u32 address, u32 *dst)
> +{
> +	int error = 0;

No need to initialize to 0.
> +
> +	error = regmap_write(ts->regmap, HIMAX_REG_CFG_SET_ADDR, address);
> +	if (error)
> +		return error;
> +
> +	error = regmap_write(ts->regmap, HIMAX_REG_CFG_INIT_READ, 0x0);
> +	if (error)
> +		return error;
> +
> +	return regmap_read(ts->regmap, HIMAX_REG_CFG_READ_VALUE, dst);

When you have a series of potentially failing statements please confinue
using if statements and finish with "return 0;".

	error = f(...);
	if (error)
		....

	return 0;

The shortcut is fine when it is the only potentially failing statement.

> +}
> +
> +static int himax_read_input_event(struct himax_ts_data *ts,
> +				  struct himax_event *event)
> +{
> +	return regmap_raw_read(ts->regmap, HIMAX_REG_READ_EVENT, event,
> +			       sizeof(*event));
> +}

I question the utility of this wrapper.

> +
> +static void himax_reset(struct himax_ts_data *ts)
> +{
> +	gpiod_set_value(ts->gpiod_rst, 1);

	gpiod_set_value_cansleep(...)

> +
> +	// Delay copied from downstream driver

Still prefer C-style comments in input code: /* ... */

> +	msleep(20);
> +	gpiod_set_value(ts->gpiod_rst, 0);

	gpiod_set_value_cansleep(...)

> +
> +	// The downstream driver doesn't contain this delay but is seems safer
> +	// to include it. The range is just a guess that seems to work well.
> +	usleep_range(1000, 1100);
> +}
> +
> +static int himax_read_product_id(struct himax_ts_data *ts, u32 *product_id)
> +{
> +	int error = himax_read_config(ts, HIMAX_CFG_PRODUCT_ID, product_id);

When doing action and check do not combine it declaration.

	int error;

	error = f(...);
	if (error)
		return error;

> +
> +	if (error)
> +		return error;
> +
> +	*product_id >>= 8;
> +	return 0;
> +}
> +
> +static int himax_check_product_id(struct himax_ts_data *ts)
> +{
> +	int error;
> +	u32 product_id;
> +
> +	error = himax_read_product_id(ts, &product_id);
> +	if (error)
> +		return error;
> +
> +	dev_dbg(&ts->client->dev, "Product id: %x\n", product_id);
> +
> +	switch (product_id) {
> +	case HIMAX_ID_83112B:
> +		return 0;
> +
> +	default:
> +		dev_err(&ts->client->dev,
> +			"Unknown product id: %x\n", product_id);
> +		return -EINVAL;
> +	}
> +}
> +
> +static int himax_setup_gpio(struct himax_ts_data *ts)
> +{
> +	int error;
> +
> +	ts->gpiod_rst = devm_gpiod_get(&ts->client->dev, "reset",
> +				       GPIOD_OUT_HIGH);
> +

	error = PTR_ERR_OR_ZERO(ts->gpiod_rst);
	if (error) {
		...
		return error;
	}

> +	if (IS_ERR(ts->gpiod_rst)) {
> +		error = PTR_ERR(ts->gpiod_rst);
> +		if (error != -EPROBE_DEFER)
> +			dev_err(&ts->client->dev,
> +				"Failed to get reset GPIO: %d\n", error);
> +		return error;
> +	}

I would not have it as helper and simply did that in himax_probe().

> +
> +	return 0;
> +}
> +
> +static int himax_input_register(struct himax_ts_data *ts)
> +{
> +	int error;
> +
> +	ts->input_dev = devm_input_allocate_device(&ts->client->dev);
> +	if (!ts->input_dev) {
> +		dev_err(&ts->client->dev, "Failed to allocate input device\n");
> +		return -ENOMEM;
> +	}
> +
> +	ts->input_dev->name = "Himax Touchscreen";
> +
> +	input_set_capability(ts->input_dev, EV_ABS, ABS_MT_POSITION_X);
> +	input_set_capability(ts->input_dev, EV_ABS, ABS_MT_POSITION_Y);
> +	input_set_abs_params(ts->input_dev, ABS_MT_WIDTH_MAJOR, 0, 200, 0, 0);
> +	input_set_abs_params(ts->input_dev, ABS_MT_TOUCH_MAJOR, 0, 200, 0, 0);
> +
> +	touchscreen_parse_properties(ts->input_dev, true, &ts->props);
> +
> +	error = input_mt_init_slots(ts->input_dev, HIMAX_MAX_POINTS,
> +				    INPUT_MT_DIRECT | INPUT_MT_DROP_UNUSED);
> +	if (error) {
> +		dev_err(&ts->client->dev,
> +			"Failed to initialize MT slots: %d\n", error);
> +		return error;
> +	}
> +
> +	error = input_register_device(ts->input_dev);
> +	if (error) {
> +		dev_err(&ts->client->dev,
> +			"Failed to register input device: %d\n", error);
> +		return error;
> +	}
> +
> +	return 0;
> +}
> +
> +static u8 himax_event_get_num_points(const struct himax_event *event)
> +{
> +	if (event->num_points == 0xff)
> +		return 0;
> +	else
> +		return event->num_points & 0x0f;
> +}
> +
> +static bool himax_event_point_is_valid(const struct himax_event_point *point)
> +{
> +	return be16_to_cpu(point->x) != HIMAX_INVALID_COORD &&
> +	       be16_to_cpu(point->y) != HIMAX_INVALID_COORD;
> +}

I am not sure if these helpers make the code clearer.

> +
> +static bool himax_process_event_point(struct himax_ts_data *ts,
> +				      const struct himax_event *event,
> +				      int point_index)
> +{
> +	const struct himax_event_point *point = &event->points[point_index];
> +	u16 x = be16_to_cpu(point->x);
> +	u16 y = be16_to_cpu(point->y);
> +	u8 w = event->majors[point_index];
> +
> +	if (!himax_event_point_is_valid(point))
> +		return false;

By using the helper we now doing be -> cpu conversion twice.

> +
> +	input_mt_slot(ts->input_dev, point_index);
> +	input_mt_report_slot_state(ts->input_dev, MT_TOOL_FINGER, true);
> +	touchscreen_report_pos(ts->input_dev, &ts->props, x, y, true);
> +	input_report_abs(ts->input_dev, ABS_MT_TOUCH_MAJOR, w);
> +	input_report_abs(ts->input_dev, ABS_MT_WIDTH_MAJOR, w);
> +	return true;
> +}
> +
> +static void himax_process_event(struct himax_ts_data *ts,
> +				const struct himax_event *event)
> +{
> +	int i;
> +	int num_points_left = himax_event_get_num_points(event);
> +
> +	for (i = 0; i < HIMAX_MAX_POINTS && num_points_left > 0; i++) {
> +		if (himax_process_event_point(ts, event, i))
> +			num_points_left--;
> +	}
> +
> +	input_mt_sync_frame(ts->input_dev);
> +	input_sync(ts->input_dev);
> +}
> +
> +static bool himax_verify_checksum(struct himax_ts_data *ts,
> +				  const struct himax_event *event)
> +{
> +	u8 *data = (u8 *)event;
> +	int i;
> +	u16 checksum = 0;
> +
> +	for (i = 0; i < sizeof(*event); i++)
> +		checksum += data[i];
> +
> +	if ((checksum & 0x00ff) != 0) {
> +		dev_err(&ts->client->dev, "Wrong event checksum: %04x\n",
> +			checksum);
> +		return false;
> +	}
> +
> +	return true;
> +}
> +
> +static int himax_handle_input(struct himax_ts_data *ts)
> +{
> +	int error;
> +	struct himax_event event;
> +
> +	error = himax_read_input_event(ts, &event);
> +	if (error) {
> +		dev_err(&ts->client->dev, "Failed to read input event: %d\n",
> +			error);
> +		return error;
> +	}
> +
> +	if (!himax_verify_checksum(ts, &event)) {
> +		// We cannot process the current event when it has an invalid
> +		// checksum but we don't consider this a fatal error.
> +		return 0;
> +	}
> +
> +	himax_process_event(ts, &event);
> +	return 0;
> +}
> +
> +static irqreturn_t himax_irq_handler(int irq, void *dev_id)
> +{
> +	struct himax_ts_data *ts = dev_id;
> +	int error = himax_handle_input(ts);
> +
> +	if (error)
> +		return IRQ_NONE;
> +
> +	return IRQ_HANDLED;
> +}
> +
> +static int himax_probe(struct i2c_client *client,
> +		       const struct i2c_device_id *id)
> +{
> +	int error;
> +	struct device *dev = &client->dev;
> +	struct himax_ts_data *ts;
> +
> +	if (!i2c_check_functionality(client->adapter, I2C_FUNC_I2C)) {
> +		dev_err(dev, "I2C check functionality failed\n");
> +		return -ENXIO;
> +	}
> +
> +	ts = devm_kzalloc(dev, sizeof(*ts), GFP_KERNEL);
> +	if (!ts)
> +		return -ENOMEM;
> +
> +	i2c_set_clientdata(client, ts);
> +	ts->client = client;
> +
> +	ts->regmap = devm_regmap_init_i2c(client, &himax_regmap_config);
> +	if (IS_ERR(ts->regmap)) {
> +		error = PTR_ERR(ts->regmap);
> +		dev_err(&client->dev,
> +			"Failed to initialize regmap: %d\n", error);
> +		return error;
> +	}
> +
> +	error = himax_setup_gpio(ts);
> +	if (error)
> +		return error;
> +
> +	himax_reset(ts);
> +
> +	error = himax_check_product_id(ts);
> +	if (error)
> +		return error;
> +
> +	error = himax_input_register(ts);
> +	if (error)
> +		return error;
> +
> +	return devm_request_threaded_irq(&client->dev, client->irq, NULL,
> +					 himax_irq_handler, IRQF_ONESHOT,
> +					 client->name, ts);
> +}
> +
> +static int himax_suspend(struct device *dev)
> +{
> +	struct himax_ts_data *ts = dev_get_drvdata(dev);
> +
> +	disable_irq(ts->client->irq);
> +	return 0;
> +}
> +
> +static int himax_resume(struct device *dev)
> +{
> +	struct himax_ts_data *ts = dev_get_drvdata(dev);
> +
> +	enable_irq(ts->client->irq);
> +	return 0;
> +}
> +
> +static SIMPLE_DEV_PM_OPS(himax_pm_ops, himax_suspend, himax_resume);

Please use DEFINE_SIMPLE_DEV_PM_OPS() and pm_sleep_ptr().

> +
> +static const struct i2c_device_id himax_ts_id[] = {
> +	{ "hx83112b", 0 },
> +	{ /* sentinel */ }
> +};
> +MODULE_DEVICE_TABLE(i2c, himax_ts_id);
> +
> +#ifdef CONFIG_OF
> +static const struct of_device_id himax_of_match[] = {
> +	{ .compatible = "himax,hx83112b" },
> +	{ /* sentinel */ }
> +};
> +MODULE_DEVICE_TABLE(of, himax_of_match);
> +#endif
> +
> +static struct i2c_driver himax_ts_driver = {
> +	.probe = himax_probe,
> +	.id_table = himax_ts_id,
> +	.driver = {
> +		.name = "Himax-hx83112b-TS",
> +		.of_match_table = of_match_ptr(himax_of_match),
> +		.pm = &himax_pm_ops,
> +	},
> +};
> +module_i2c_driver(himax_ts_driver);
> +
> +MODULE_AUTHOR("Job Noorman <job@...rman.info>");
> +MODULE_DESCRIPTION("Himax hx83112b touchscreen driver");
> +MODULE_LICENSE("GPL");
> -- 
> 2.38.0
> 

Thanks.

-- 
Dmitry

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