Date:	Mon, 16 May 2011 09:44:27 -0700
From:	Dmitry Torokhov <dmitry.torokhov@...il.com>
To:	Grant Likely <grant.likely@...retlab.ca>
Cc:	linux-kernel@...r.kernel.org, linux-input@...r.kernel.org
Subject: Re: [RFC PATCH] input: Add wiichuck driver

Hi Grant,

On Thu, May 12, 2011 at 06:29:44AM +0200, Grant Likely wrote:
> This patch adds a driver for the Nintendo Nunchuck (wiimote accessory)
> attached to an i2c bus via something like a wiichuck adapter board
> from Sparkfun.
> 
> Signed-off-by: Grant Likely <grant.likely@...retlab.ca>
> ---
> 
> This is RFC because the driver doesn't completely work yet.  The
> joystick and buttons work fine.  There is a bug with the accelerometer
> reporting though (nothing gets reported), and I'm not even sure I'm
> using the right input type for reporting accelerometer values.

Looks quite reasonable and I think that ABS_Rx is reasonable events for
accelerometer in this particular case.

A few more comments below.

> Comments welcome.
> 
>  drivers/input/joystick/Kconfig    |    8 +
>  drivers/input/joystick/Makefile   |    1 
>  drivers/input/joystick/wiichuck.c |  225 +++++++++++++++++++++++++++++++++++++
>  3 files changed, 234 insertions(+), 0 deletions(-)
>  create mode 100644 drivers/input/joystick/wiichuck.c
> 
> diff --git a/drivers/input/joystick/Kconfig b/drivers/input/joystick/Kconfig
> index 56eb471..79f18db 100644
> --- a/drivers/input/joystick/Kconfig
> +++ b/drivers/input/joystick/Kconfig
> @@ -193,6 +193,14 @@ config JOYSTICK_TWIDJOY
>  	  To compile this driver as a module, choose M here: the
>  	  module will be called twidjoy.
>  
> +config JOYSTICK_WIICHUCK
> +	tristate "Nintendo Nunchuck on i2c bus"
> +	depends on I2C
> +	select INPUT_POLLDEV
> +	help
> +	  Say Y here if you have a Nintendo Nunchuck directly attached to
> +	  the machine's i2c bus.
> +

	To compile this driver as a module, ...

>  config JOYSTICK_ZHENHUA
>  	tristate "5-byte Zhenhua RC transmitter"
>  	select SERIO
> diff --git a/drivers/input/joystick/Makefile b/drivers/input/joystick/Makefile
> index 92dc0de..78466d6 100644
> --- a/drivers/input/joystick/Makefile
> +++ b/drivers/input/joystick/Makefile
> @@ -29,6 +29,7 @@ obj-$(CONFIG_JOYSTICK_TMDC)		+= tmdc.o
>  obj-$(CONFIG_JOYSTICK_TURBOGRAFX)	+= turbografx.o
>  obj-$(CONFIG_JOYSTICK_TWIDJOY)		+= twidjoy.o
>  obj-$(CONFIG_JOYSTICK_WARRIOR)		+= warrior.o
> +obj-$(CONFIG_JOYSTICK_WIICHUCK)		+= wiichuck.o
>  obj-$(CONFIG_JOYSTICK_XPAD)		+= xpad.o
>  obj-$(CONFIG_JOYSTICK_ZHENHUA)		+= zhenhua.o
>  obj-$(CONFIG_JOYSTICK_WALKERA0701)	+= walkera0701.o
> diff --git a/drivers/input/joystick/wiichuck.c b/drivers/input/joystick/wiichuck.c
> new file mode 100644
> index 0000000..2afc274
> --- /dev/null
> +++ b/drivers/input/joystick/wiichuck.c
> @@ -0,0 +1,225 @@
> +/*
> + * Nintendo Nunchuck driver for i2c connection.
> + *
> + * Copyright (c) 2011 Secret Lab Technologies Ltd.
> + *
> + * This program is free software; you can redistribute it and/or modify
> + * it under the terms of the GNU General Public License as published by
> + * the Free Software Foundation; either version 2 of the License, or
> + * (at your option) any later version.
> + *
> + * This program is distributed in the hope that it will be useful,
> + * but WITHOUT ANY WARRANTY; without even the implied warranty of
> + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
> + * GNU General Public License for more details.
> + *
> + * You should have received a copy of the GNU General Public License
> + * along with this program; if not, write to the Free Software
> + * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
> + *
> + */
> +
> +#include <linux/delay.h>
> +#include <linux/i2c.h>
> +#include <linux/interrupt.h>
> +#include <linux/input.h>
> +#include <linux/input-polldev.h>
> +#include <linux/mod_devicetable.h>
> +#include <linux/slab.h>
> +
> +MODULE_AUTHOR("Grant Likely <grant.likely@...retlab.ca>");
> +MODULE_DESCRIPTION("Nintendo Nunchuck driver");
> +MODULE_LICENSE("GPL");
> +
> +#define WIICHUCK_JOY_MAX_AXIS	220
> +#define WIICHUCK_JOY_MIN_AXIS	30
> +#define WIICHUCK_JOY_FUZZ	4
> +#define WIICHUCK_JOY_FLAT	8
> +
> +struct wiichuck_device {
> +	struct input_polled_dev *poll_dev;
> +	struct i2c_client *i2c_client;
> +	int state;
> +};
> +
> +static void wiichuck_poll(struct input_polled_dev *poll_dev)
> +{
> +	struct wiichuck_device *wiichuck = poll_dev->private;
> +	struct i2c_client *i2c = wiichuck->i2c_client;
> +	static uint8_t cmd_byte = 0;
> +	struct i2c_msg cmd_msg =
> +		{ .addr = i2c->addr, .len = 1, .buf = &cmd_byte };
> +	uint8_t b[6];

As mentioned by others these buffers should not be on stack.

> +	struct i2c_msg data_msg =
> +		{ .addr = i2c->addr, .flags = I2C_M_RD, .len = 6, .buf = b };
> +	int jx, jy, ax, ay, az;
> +	bool c, z;
> +
> +	switch (wiichuck->state) {
> +	case 0:
> +		i2c_transfer(i2c->adapter, &cmd_msg, 1);
> +		wiichuck->state = 1;

Do you really need to have a state machine here? Why not do both
transfers in one poll invocation?

> +		break;
> +
> +	case 1:
> +		i2c_transfer(i2c->adapter, &data_msg, 1);
> +
> +		jx = b[0];
> +		jy = b[1];
> +		ax = (b[2] << 2) & ((b[5] >> 2) & 0x3);
> +		ay = (b[3] << 2) & ((b[5] >> 4) & 0x3);
> +		az = (b[4] << 2) & ((b[5] >> 6) & 0x3);
> +		z = !(b[5] & 1);
> +		c = !(b[5] & 2);
> +
> +		input_report_abs(poll_dev->input, ABS_X, jx);
> +		input_report_abs(poll_dev->input, ABS_Y, jy);
> +		input_report_abs(poll_dev->input, ABS_RX, ax);
> +		input_report_abs(poll_dev->input, ABS_RY, ax);
> +		input_report_abs(poll_dev->input, ABS_RZ, ay);
> +		input_report_key(poll_dev->input, BTN_C, c);
> +		input_report_key(poll_dev->input, BTN_Z, z);
> +		input_sync(poll_dev->input);
> +
> +		wiichuck->state = 0;
> +		dev_dbg(&i2c->dev, "wiichuck: j=%.3i,%.3i a=%.3x,%.3x,%.3x %c%c\n",
> +			jx,jy, ax,ay,az, c ? 'C' : 'c', z ? 'Z' : 'z');
> +		break;
> +
> +	default:
> +		wiichuck->state = 0;
> +	}
> +}
> +
> +static void wiichuck_open(struct input_polled_dev *poll_dev)
> +{
> +	struct wiichuck_device *wiichuck = poll_dev->private;
> +	struct i2c_client *i2c = wiichuck->i2c_client;
> +	static uint8_t data1[2] = { 0xf0, 0x55 };
> +	static uint8_t data2[2] = { 0xfb, 0x00 };
> +	struct i2c_msg msg1 = { .addr = i2c->addr, .len = 2, .buf = data1 };
> +	struct i2c_msg msg2 = { .addr = i2c->addr, .len = 2, .buf = data2 };
> +
> +	i2c_transfer(i2c->adapter, &msg1, 1);
> +	i2c_transfer(i2c->adapter, &msg2, 1);
> +	wiichuck->state = 0;
> +
> +	dev_dbg(&i2c->dev, "wiichuck open()\n");
> +}
> +
> +static int __devinit wiichuck_probe(struct i2c_client *client,
> +				const struct i2c_device_id *id)
> +{
> +	struct wiichuck_device *wiichuck;
> +	struct input_polled_dev *poll_dev;
> +	struct input_dev *input_dev;
> +	int rc;
> +
> +	wiichuck = kzalloc(sizeof(*wiichuck), GFP_KERNEL);
> +	if (!wiichuck)
> +		return -ENOMEM;
> +
> +	poll_dev = input_allocate_polled_device();
> +	if (!poll_dev) {
> +		rc = -ENOMEM;
> +		goto err_alloc;
> +	}
> +
> +	wiichuck->i2c_client = client;
> +	wiichuck->poll_dev = poll_dev;
> +
> +	poll_dev->private = wiichuck;
> +	poll_dev->poll = wiichuck_poll;
> +	poll_dev->poll_interval = 50; /* Poll every 50ms */
> +	poll_dev->open = wiichuck_open;
> +
> +	input_dev = poll_dev->input;
> +	input_dev->name = "Nintendo Nunchuck";
> +	input_dev->id.bustype = BUS_I2C;
> +	input_dev->dev.parent = &client->dev;
> +
> +	/* Declare the events generated by this driver */
> +	set_bit(EV_ABS, input_dev->evbit);
> +	set_bit(ABS_X, input_dev->absbit); /* joystick */
> +	set_bit(ABS_Y, input_dev->absbit);
> +	set_bit(ABS_RX, input_dev->absbit); /* accelerometer */
> +	set_bit(ABS_RY, input_dev->absbit);
> +	set_bit(ABS_RZ, input_dev->absbit);
> +
> +	set_bit(EV_KEY, input_dev->evbit);
> +	set_bit(BTN_C, input_dev->keybit); /* buttons */
> +	set_bit(BTN_Z, input_dev->keybit);

I prefer __set_bit() here since there is no concurrency.

> +
> +	input_set_abs_params(input_dev, ABS_X, 30, 220, 4, 8);
> +	input_set_abs_params(input_dev, ABS_Y, 40, 200, 4, 8);
> +	input_set_abs_params(input_dev, ABS_RX, 0, 0x3ff, 4, 8);
> +	input_set_abs_params(input_dev, ABS_RY, 0, 0x3ff, 4, 8);
> +	input_set_abs_params(input_dev, ABS_RZ, 0, 0x3ff, 4, 8);
> +
> +	rc = input_register_polled_device(wiichuck->poll_dev);
> +	if (rc) {
> +		dev_err(&client->dev, "Failed to register input device\n");
> +		goto err_register;
> +	}
> +
> +	i2c_set_clientdata(client, wiichuck);
> +
> +	return 0;
> +
> + err_register:
> +	input_free_polled_device(poll_dev);
> + err_alloc:
> +	kfree(wiichuck);
> +
> +	return rc;
> +}
> +
> +static int __devexit wiichuck_remove(struct i2c_client *client)
> +{
> +	struct wiichuck_device *wiichuck = i2c_get_clientdata(client);
> +
> +	i2c_set_clientdata(client, NULL);
> +	input_unregister_polled_device(wiichuck->poll_dev);
> +	input_free_polled_device(wiichuck->poll_dev);
> +	kfree(wiichuck);
> +
> +	return 0;
> +}
> +
> +static const struct i2c_device_id wiichuck_id[] = {
> +	{ "nunchuck", 0 },
> +	{ }
> +};
> +MODULE_DEVICE_TABLE(i2c, wiichuck_id);
> +
> +#ifdef CONFIG_OF
> +static struct of_device_id wiichuck_match_table[] __devinitdata = {
> +	{ .compatible = "nintendo,nunchuck", },
> +	{ }
> +};
> +#else
> +#define wiichuck_match_table NULL
> +#endif
> +
> +static struct i2c_driver wiichuck_driver = {
> +	.driver = {
> +		.name = "nunchuck",
> +		.owner = THIS_MODULE,
> +		.of_match_table = wiichuck_match_table,
> +	},
> +	.probe		= wiichuck_probe,
> +	.remove		= __devexit_p(wiichuck_remove),
> +	.id_table	= wiichuck_id,
> +};
> +
> +static int __init wiichuck_init(void)
> +{
> +	return i2c_add_driver(&wiichuck_driver);
> +}
> +module_init(wiichuck_init);
> +
> +static void __exit wiichuck_exit(void)
> +{
> +	i2c_del_driver(&wiichuck_driver);
> +}
> +module_exit(wiichuck_exit);
> 

Thanks.

-- 
Dmitry
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