Re: [PATCH] Input: Add I2C attached EETI EXC3000 multi touch driver

From: Dmitry Torokhov <dmitry.torokhov@gmail.com>
To: Ahmet Inan <inan@distec.de>
Cc: linux-input@vger.kernel.org, Ahmet Inan <xdsopl@gmail.com>
Subject: Re: [PATCH] Input: Add I2C attached EETI EXC3000 multi touch driver
Date: Thu, 21 Sep 2017 14:15:51 -0700	[thread overview]
Message-ID: <20170921211551.GB15858@dtor-ws> (raw)
In-Reply-To: <20170920135129.10283-1-inan@distec.de>

Hi Ahmet,

On Wed, Sep 20, 2017 at 03:51:29PM +0200, Ahmet Inan wrote:
> The 3000 series have a new protocol which allows to report up to 5 points
> in a single 66 byte frame. One must always read in 66 byte frames.
> To support up to 10 points, two consecutive frames need to be read:
> The first frame says how many points until sync.
> The second frame must say zero points or be discarded.
> 
> To be able to work with the higher 400KHz I2C bus rate, one must
> successfully send a special package prior _each_ read or the controller
> will refuse to cooperate.
> 
> It is important not to rely on the i2c_master_recv return value:
> Ignoring failed transfers sometimes causes hanging touch events, as the
> controller thinks that the transfer succeeded and won't resend the event.

This statement worries me, because you are basically end up reporting
garbage. Does the controller sends all active contacts in each frame, or
only changed ones? You can use INPUT_MT_DROP_UNUSED to let input core
automatically drop contacts that were not reported within the last
frame. And fire up a timer to release everything if last transfer errors
out.

> 
> This is a minimal implementation based on egalax_i2c.c (which can be found
> on the internet) and egalax_ts.c but without the vendor interface and no
> power management support.
> 
> Signed-off-by: Ahmet Inan <inan@distec.de>
> ---
>  .../bindings/input/touchscreen/exc3000.txt         |  18 +++
>  drivers/input/touchscreen/Kconfig                  |  10 ++
>  drivers/input/touchscreen/Makefile                 |   1 +
>  drivers/input/touchscreen/exc3000.c                | 154 +++++++++++++++++++++
>  4 files changed, 183 insertions(+)
>  create mode 100644 Documentation/devicetree/bindings/input/touchscreen/exc3000.txt
>  create mode 100644 drivers/input/touchscreen/exc3000.c
> 
> diff --git a/Documentation/devicetree/bindings/input/touchscreen/exc3000.txt b/Documentation/devicetree/bindings/input/touchscreen/exc3000.txt
> new file mode 100644
> index 000000000000..9b6f0919abd0
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/input/touchscreen/exc3000.txt
> @@ -0,0 +1,18 @@
> +* EETI EXC3000 Multiple Touch Controller
> +
> +Required properties:
> +- compatible: must be "eeti,exc3000"
> +- reg: i2c slave address
> +- interrupt-parent: the phandle for the interrupt controller
> +- interrupts: touch controller interrupt
> +- irq-gpios: the gpio pin to be used as irq pin
> +
> +Example:
> +
> +	exc3000@2a {
> +		compatible = "eeti,exc3000";
> +		reg = <0x2a>;
> +		interrupt-parent = <&gpio1>;
> +		interrupts = <9 2>;
> +		irq-gpios = <&gpio1 9 0>;
> +	};
> diff --git a/drivers/input/touchscreen/Kconfig b/drivers/input/touchscreen/Kconfig
> index 0bf78ff1ae88..9ea2d9287b38 100644
> --- a/drivers/input/touchscreen/Kconfig
> +++ b/drivers/input/touchscreen/Kconfig
> @@ -314,6 +314,16 @@ config TOUCHSCREEN_EGALAX_SERIAL
>  	  To compile this driver as a module, choose M here: the
>  	  module will be called egalax_ts_serial.
>  
> +config TOUCHSCREEN_EXC3000
> +	tristate "EETI EXC3000 multi-touch panel support"
> +	depends on I2C
> +	help
> +	  Say Y here to enable support for I2C connected EETI
> +	  EXC3000 multi-touch panels.
> +
> +	  To compile this driver as a module, choose M here: the
> +	  module will be called exc3000.
> +
>  config TOUCHSCREEN_FUJITSU
>  	tristate "Fujitsu serial touchscreen"
>  	select SERIO
> diff --git a/drivers/input/touchscreen/Makefile b/drivers/input/touchscreen/Makefile
> index f720bc30ada9..48118379fee7 100644
> --- a/drivers/input/touchscreen/Makefile
> +++ b/drivers/input/touchscreen/Makefile
> @@ -38,6 +38,7 @@ obj-$(CONFIG_TOUCHSCREEN_ELAN)		+= elants_i2c.o
>  obj-$(CONFIG_TOUCHSCREEN_ELO)		+= elo.o
>  obj-$(CONFIG_TOUCHSCREEN_EGALAX)	+= egalax_ts.o
>  obj-$(CONFIG_TOUCHSCREEN_EGALAX_SERIAL)	+= egalax_ts_serial.o
> +obj-$(CONFIG_TOUCHSCREEN_EXC3000)	+= exc3000.o
>  obj-$(CONFIG_TOUCHSCREEN_FUJITSU)	+= fujitsu_ts.o
>  obj-$(CONFIG_TOUCHSCREEN_GOODIX)	+= goodix.o
>  obj-$(CONFIG_TOUCHSCREEN_ILI210X)	+= ili210x.o
> diff --git a/drivers/input/touchscreen/exc3000.c b/drivers/input/touchscreen/exc3000.c
> new file mode 100644
> index 000000000000..c8a1a8b04bf2
> --- /dev/null
> +++ b/drivers/input/touchscreen/exc3000.c
> @@ -0,0 +1,154 @@
> +/*
> + * Driver for I2C connected EETI EXC3000 multiple touch controller
> + *
> + * Copyright (C) 2017 Ahmet Inan <inan@distec.de>
> + *
> + * minimal implementation based on egalax_ts.c and egalax_i2c.c
> + *
> + * This program is free software; you can redistribute it and/or modify
> + * it under the terms of the GNU General Public License version 2 as
> + * published by the Free Software Foundation.
> + */
> +
> +#include <linux/module.h>
> +#include <linux/interrupt.h>
> +#include <linux/i2c.h>
> +#include <linux/input.h>
> +#include <linux/irq.h>
> +#include <linux/input/mt.h>
> +
> +#define NUM_SLOTS 10
> +#define PER_FRAME 5

What per frame?

#define EXC3000_NUM_SLOTS	10
#define EXC3000_SLOTS_PER_FRAME	5

> +#define LEN_FRAME 66
> +#define LEN_POINT 10
> +
> +struct exc3000_data {
> +	struct i2c_client *client;
> +	struct input_dev *input;
> +	unsigned char buf[2 * LEN_FRAME];

u8 for byte data.

> +};
> +
> +static void exc3000_process(struct input_dev *input,
> +		unsigned char *buf, int num)
> +{
> +	while (num--) {
> +		int dn, id, x, y;
> +
> +		dn = buf[0] & 1;
> +		id = buf[1];
> +		x = (buf[3] << 8) | buf[2];

		get_unaligned_le16()

> +		y = (buf[5] << 8) | buf[4];

		get_unaligned_le16()

Also, why parse these for released contacts?

> +		buf += LEN_POINT;
> +		if (id >= NUM_SLOTS)
> +			continue;
> +		input_mt_slot(input, id);
> +		input_mt_report_slot_state(input, MT_TOOL_FINGER, dn);
> +		if (dn) {
> +			input_report_abs(input, ABS_MT_POSITION_X, x);
> +			input_report_abs(input, ABS_MT_POSITION_Y, y);
> +		}
> +	}
> +}
> +
> +static int exc3000_read(struct i2c_client *client, unsigned char *buf)
> +{
> +	if (i2c_master_send(client, "'", 2) != 2)
> +		return 1;
> +	memset(buf, 0, LEN_FRAME);
> +	i2c_master_recv(client, buf, LEN_FRAME);
> +	return buf[0] != 0x42 || buf[1] != 0x00 || buf[2] != 0x06;
> +}
> +
> +static irqreturn_t exc3000_interrupt(int irq, void *dev_id)
> +{
> +	struct exc3000_data *data = (struct exc3000_data *)dev_id;

No need to cast.

> +	struct i2c_client *client = data->client;
> +	struct input_dev *input = data->input;
> +	unsigned char *buf = data->buf;
> +
> +	if (exc3000_read(client, buf) || !buf[3] || buf[3] > NUM_SLOTS)
> +		return IRQ_HANDLED;
> +	if (buf[3] <= PER_FRAME) {
> +		exc3000_process(input, buf + 4, buf[3]);
> +	} else {
> +		if (exc3000_read(client, buf + LEN_FRAME) || buf[LEN_FRAME + 3])
> +			return IRQ_HANDLED;
> +		exc3000_process(input, buf + 4, PER_FRAME);
> +		exc3000_process(input, buf + LEN_FRAME + 4, buf[3] - PER_FRAME);
> +	}
> +	input_mt_report_pointer_emulation(input, true);

Not needed with right flags to input_mt_init_slots (INPUT_MT_DIRECT) and
call to input_mt_sync_frame() here.

> +	input_sync(input);
> +	return IRQ_HANDLED;
> +}
> +
> +static int exc3000_probe(struct i2c_client *client,
> +		const struct i2c_device_id *id)
> +{
> +	struct exc3000_data *data;
> +	struct input_dev *input;
> +	int error;
> +
> +	data = (struct exc3000_data *)devm_kzalloc(&client->dev,

No need to cast.

> +			sizeof(struct exc3000_data), GFP_KERNEL);

			sizeof(*data)

> +	if (!data)
> +		return -ENOMEM;
> +
> +	input = devm_input_allocate_device(&client->dev);
> +	if (!input)
> +		return -ENOMEM;
> +
> +	input->name = "EETI EXC3000 Touch Screen";
> +	input->id.bustype = BUS_I2C;
> +
> +	__set_bit(EV_ABS, input->evbit);

Not needed as input_set_abs_params() does this for you.

> +	__set_bit(EV_KEY, input->evbit);
> +	__set_bit(BTN_TOUCH, input->keybit);

	input_set_capability(input, EV_KEY, BTN_TOUCH);

> +	input_set_abs_params(input, ABS_X, 0, 4096, 0, 0);
> +	input_set_abs_params(input, ABS_Y, 0, 4096, 0, 0);
> +	input_set_abs_params(input, ABS_MT_POSITION_X, 0, 4096, 0, 0);
> +	input_set_abs_params(input, ABS_MT_POSITION_Y, 0, 4096, 0, 0);

	touchscreen_parse_properties() ?

> +	input_mt_init_slots(input, NUM_SLOTS, 0);

Needs error handling. INPUT_MT_DIRECT?

> +
> +	error = input_register_device(input);
> +	if (error)
> +		return error;
> +
> +	data->input = input;
> +	data->client = client;
> +	i2c_set_clientdata(client, data);
> +
> +	error = devm_request_threaded_irq(&client->dev, client->irq, NULL,
> +			exc3000_interrupt, IRQF_TRIGGER_LOW | IRQF_ONESHOT,

Do not specify trigger explicitly, rely on platform to set it up.

> +			client->name, data);
> +	if (error)
> +		return error;
> +
> +	return 0;
> +}
> +
> +static const struct i2c_device_id exc3000_id[] = {
> +	{ "exc3000", 0 },
> +	{ }
> +};
> +

#ifdef CONFIG_OF

> +static const struct of_device_id exc3000_dt_ids[] = {
> +	{ .compatible = "eeti,exc3000" },
> +	{ }
> +};

#endif

> +
> +MODULE_DEVICE_TABLE(i2c, exc3000_id);
> +
> +static struct i2c_driver exc3000_driver = {
> +	.driver = {
> +		.name	= "exc3000",
> +		.of_match_table = exc3000_dt_ids,

of_match_ptr()

> +	},
> +	.id_table	= exc3000_id,
> +	.probe		= exc3000_probe,
> +};
> +
> +module_i2c_driver(exc3000_driver);
> +
> +MODULE_AUTHOR("Ahmet Inan <inan@distec.de>");
> +MODULE_DESCRIPTION("I2C connected EETI EXC3000 multiple touch controller driver");
> +MODULE_LICENSE("GPL");
> -- 
> 2.11.0
>

Thanks.

-- 
Dmitry