Re: [PATCH v2] input/misc: PCF8574 I2C keypad input device driver

[Dmitry Torokhov <dmitry.torokhov@gmail.com>]

On Tue, Mar 09, 2010 at 04:01:53PM -0500, Mike Frysinger wrote:
> From: Bryan Wu <cooloney@kernel.org>
> 
> Signed-off-by: Bryan Wu <cooloney@kernel.org>
> Signed-off-by: Mike Frysinger <vapier@gentoo.org>
> ---
> v2
> 	- process all feedback from Dmitry except for threaded irqs; that'll have to be done later

Could I ask why? As it stands the remove() is racy WRT to a work
running. But if you simply add cancel_work_sync() you'll risk leaving
unbalanced enable_irq()/disable_irq().

A few more comments I missed first time around:

> 
>  drivers/input/misc/Kconfig          |   10 ++
>  drivers/input/misc/Makefile         |    1 +
>  drivers/input/misc/pcf8574_keypad.c |  251 +++++++++++++++++++++++++++++++++++
>  3 files changed, 262 insertions(+), 0 deletions(-)
>  create mode 100644 drivers/input/misc/pcf8574_keypad.c
> 
> diff --git a/drivers/input/misc/Kconfig b/drivers/input/misc/Kconfig
> index 49a31bd..fa97c58 100644
> --- a/drivers/input/misc/Kconfig
> +++ b/drivers/input/misc/Kconfig
> @@ -396,4 +396,14 @@ config INPUT_ADXL34X_SPI
>  	  To compile this driver as a module, choose M here: the
>  	  module will be called adxl34x-spi.
>  
> +config INPUT_PCF8574
> +	tristate "PCF8574 Keypad input device"
> +	depends on I2C && EXPERIMENTAL
> +	help
> +	  Say Y here if you want to support a keypad connetced via I2C
> +	  with a PCF8574.
> +
> +	  To compile this driver as a module, choose M here: the
> +	  module will be called pcf8574_keypad.
> +
>  endif
> diff --git a/drivers/input/misc/Makefile b/drivers/input/misc/Makefile
> index 775db74..8107c57 100644
> --- a/drivers/input/misc/Makefile
> +++ b/drivers/input/misc/Makefile
> @@ -9,6 +9,7 @@ obj-$(CONFIG_INPUT_AD714X)		+= ad714x.o
>  obj-$(CONFIG_INPUT_AD714X_I2C)		+= ad714x-i2c.o
>  obj-$(CONFIG_INPUT_AD714X_SPI)		+= ad714x-spi.o
>  obj-$(CONFIG_INPUT_APANEL)		+= apanel.o
> +obj-$(CONFIG_INPUT_PCF8574)		+= pcf8574_keypad.o
>  obj-$(CONFIG_INPUT_ATI_REMOTE)		+= ati_remote.o
>  obj-$(CONFIG_INPUT_ATI_REMOTE2)		+= ati_remote2.o
>  obj-$(CONFIG_INPUT_ATLAS_BTNS)		+= atlas_btns.o
> diff --git a/drivers/input/misc/pcf8574_keypad.c b/drivers/input/misc/pcf8574_keypad.c
> new file mode 100644
> index 0000000..8b52a7e
> --- /dev/null
> +++ b/drivers/input/misc/pcf8574_keypad.c
> @@ -0,0 +1,251 @@
> +/*
> + * Driver for a keypad w/16 buttons connected to a PCF8574 I2C I/O expander
> + *
> + * Copyright 2005-2008 Analog Devices Inc.
> + *
> + * Licensed under the GPL-2 or later.
> + */
> +
> +#include <linux/module.h>
> +#include <linux/init.h>
> +#include <linux/input.h>
> +#include <linux/interrupt.h>
> +#include <linux/i2c.h>
> +#include <linux/workqueue.h>
> +
> +#define DRV_NAME "pcf8574_keypad"
> +
> +static const unsigned char pcf8574_kp_btncode[] = {
> +	[0] = KEY_RESERVED,
> +	[1] = KEY_ENTER,
> +	[2] = KEY_BACKSLASH,
> +	[3] = KEY_0,
> +	[4] = KEY_RIGHTBRACE,
> +	[5] = KEY_C,
> +	[6] = KEY_9,
> +	[7] = KEY_8,
> +	[8] = KEY_7,
> +	[9] = KEY_B,
> +	[10] = KEY_6,
> +	[11] = KEY_5,
> +	[12] = KEY_4,
> +	[13] = KEY_A,
> +	[14] = KEY_3,
> +	[15] = KEY_2,
> +	[16] = KEY_1
> +};
> +
> +struct kp_data {
> +	unsigned char btncode[17];

Unsigned short here. Also ARRAY_SIZE(pcf8574_kp_btncode).

> +	struct input_dev *idev;
> +	struct i2c_client *client;
> +	char name[64];
> +	char phys[32];
> +	unsigned char laststate;
> +	unsigned char statechanged;
> +	unsigned long events_sent;
> +	struct work_struct pcf8574_kp_work;
> +};
> +
> +static short read_state(struct kp_data *lp)
> +{
> +	unsigned char x, y, a, b;
> +
> +	if (lp->client) {

No need for this check - I do not see how we can end up with lp->client
being NULL here.

> +		i2c_smbus_write_byte(lp->client, 240);
> +		x = 0xF & (~(i2c_smbus_read_byte(lp->client) >> 4));
> +
> +		i2c_smbus_write_byte(lp->client, 15);
> +		y = 0xF & (~i2c_smbus_read_byte(lp->client));
> +
> +		for (a = 0; x > 0; a++)
> +			x = x >> 1;
> +		for (b = 0; y > 0; b++)
> +			y = y >> 1;
> +
> +		return ((a - 1) * 4) + b;
> +	}
> +
> +	return -1;
> +}
> +
> +static void check_and_notify(struct work_struct *work)
> +{
> +	struct kp_data *lp =
> +	    container_of(work, struct kp_data, pcf8574_kp_work);
> +	unsigned char nextstate = read_state(lp);
> +
> +	lp->statechanged = lp->laststate ^ nextstate;
> +
> +	if (lp->statechanged)

Hmm, why is it in lp? Local variable (or even lp->laststate ^ nextstate
expression) would work just fine.

> +		input_report_key(lp->idev,
> +				 nextstate > 17 ? lp->btncode[lp->laststate] :
> +				 lp->btncode[nextstate],
> +				 nextstate > 17 ? 0 : 1);
> +	lp->laststate = nextstate;
> +
> +	input_sync(lp->idev);
> +	enable_irq(lp->client->irq);
> +}
> +
> +static irqreturn_t pcf8574_kp_irq_handler(int irq, void *dev_id)
> +{
> +	struct kp_data *lp = dev_id;
> +
> +	disable_irq_nosync(lp->client->irq);
> +	schedule_work(&lp->pcf8574_kp_work);
> +
> +	return IRQ_HANDLED;
> +}
> +
> +static int __devinit pcf8574_kp_probe(struct i2c_client *client, const struct i2c_device_id *id)
> +{
> +	int i, ret;
> +	struct input_dev *idev;
> +	struct kp_data *lp;
> +
> +	if (i2c_smbus_write_byte(client, 240) < 0) {
> +		dev_err(&client->dev, "probe: write fail\n");
> +		return -ENODEV;
> +	}
> +
> +	lp = kzalloc(sizeof(*lp), GFP_KERNEL);
> +	if (!lp)
> +		return -ENOMEM;
> +	lp->client = client;
> +
> +	idev = input_allocate_device();
> +	if (!idev) {
> +		dev_err(&client->dev, "Can't allocate input device\n");
> +		ret = -ENOMEM;
> +		goto fail_allocate;
> +	}
> +
> +	lp->idev = idev;
> +	memcpy(lp->btncode, pcf8574_kp_btncode, sizeof(pcf8574_kp_btncode));
> +
> +	idev->evbit[0] = 0;
> +
> +	idev->evbit[0] |= BIT_MASK(EV_KEY);
> +	idev->keycode = lp->btncode;
> +	idev->keycodesize = sizeof(pcf8574_kp_btncode);

Umm 17 bytes is a bit too much ;) sizeof(lp->btncode[0]); is more
appropriate.

> +	idev->keycodemax = ARRAY_SIZE(pcf8574_kp_btncode);
> +
> +	for (i = 0; i < ARRAY_SIZE(pcf8574_kp_btncode); ++i)
> +		__set_bit(lp->btncode[i] & KEY_MAX, idev->keybit);
> +
> +	__clear_bit(KEY_RESERVED, idev->keybit);
> +
> +	sprintf(lp->name, DRV_NAME);
> +	sprintf(lp->phys, "kp_data/input0");
> +
> +	idev->name = lp->name;
> +	idev->phys = lp->phys;
> +	idev->id.bustype = BUS_I2C;
> +	idev->id.vendor = 0x0001;
> +	idev->id.product = 0x0001;
> +	idev->id.version = 0x0100;
> +
> +	input_set_drvdata(idev, lp);
> +
> +	ret = input_register_device(idev);
> +	if (ret) {
> +		dev_err(&client->dev, "input_register_device() failed\n");
> +		goto fail_register;
> +	}
> +
> +	lp->statechanged = 0x0;
> +
> +	lp->laststate = read_state(lp);
> +
> +	/* Set up our workqueue. */
> +	INIT_WORK(&lp->pcf8574_kp_work, check_and_notify);
> +
> +	i2c_set_clientdata(client, lp);
> +
> +	ret = request_irq(client->irq, pcf8574_kp_irq_handler,
> +		IRQF_TRIGGER_LOW, DRV_NAME, lp);
> +	if (ret) {
> +		dev_err(&client->dev, "IRQ %d is not free\n", client->irq);
> +		goto fail_irq;
> +	}
> +
> +	return 0;
> +
> + fail_irq:
> +	input_unregister_device(idev);

You need "idev = NULL;" here.

> + fail_register:
> +	input_set_drvdata(idev, NULL);
> +	input_free_device(idev);
> + fail_allocate:
> +	kfree(lp);
> +
> +	return ret;
> +}
> +
> +static int __devexit pcf8574_kp_remove(struct i2c_client *client)
> +{
> +	struct kp_data *lp = i2c_get_clientdata(client);
> +
> +	if (client->irq > 0)

No need for this check.

> +		free_irq(client->irq, lp);
> +
> +	input_set_drvdata(lp->idev, NULL);
> +	input_unregister_device(lp->idev);
> +	kfree(lp);
> +
> +	i2c_set_clientdata(client, NULL);
> +
> +	return 0;
> +}
> +
> +#ifdef CONFIG_PM
> +static int pcf8574_kp_resume(struct i2c_client *client)
> +{
> +	enable_irq(client->irq);
> +	return 0;
> +}
> +
> +static int pcf8574_kp_suspend(struct i2c_client *client, pm_message_t mesg)
> +{
> +	disable_irq(client->irq);
> +	return 0;
> +}
> +#else
> +# define pcf8574_kp_resume  NULL
> +# define pcf8574_kp_suspend NULL
> +#endif
> +
> +static const struct i2c_device_id pcf8574_kp_id[] = {
> +	{ DRV_NAME, 0 },
> +	{ }
> +};
> +MODULE_DEVICE_TABLE(i2c, pcf8574_kp_id);
> +
> +static struct i2c_driver pcf8574_kp_driver = {
> +	.driver = {
> +		.name  = DRV_NAME,
> +		.owner = THIS_MODULE
> +	},
> +	.probe    = pcf8574_kp_probe,
> +	.remove   = __devexit_p(pcf8574_kp_remove),
> +	.suspend  = pcf8574_kp_suspend,
> +	.resume   = pcf8574_kp_resume,
> +	.id_table = pcf8574_kp_id,
> +};
> +
> +static int __init pcf8574_kp_init(void)
> +{
> +	return i2c_add_driver(&pcf8574_kp_driver);
> +}
> +module_init(pcf8574_kp_init);
> +
> +static void __exit pcf8574_kp_exit(void)
> +{
> +	i2c_del_driver(&pcf8574_kp_driver);
> +}
> +module_exit(pcf8574_kp_exit);
> +
> +MODULE_AUTHOR("Michael Hennerich");
> +MODULE_DESCRIPTION("Keypad input driver for 16 keys connected to PCF8574");
> +MODULE_LICENSE("GPL");
> -- 
> 1.7.0.2
> 

-- 
Dmitry