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Subject: RE: input: add mxc-keypad driver to support the keypad interface present in the mxc application processors family.
Date: Fri, 8 Jan 2010 15:33:12 -0500
Message-ID: <BD79186B4FD85F4B8E60E381CAEE190902089738@mi8nycmail19.Mi8.com>
In-Reply-To: <1262977099.2050.75.camel@climbing-alby>
Thread-Topic: input: add mxc-keypad driver to support the keypad interface present in the mxc application processors family.
Thread-Index: AcqQlMlC6Z7H4oMXQ9uC0Qn/PbEXqwACTu4g
References: <1262977099.2050.75.camel@climbing-alby>
From: "H Hartley Sweeten" <hartleys@visionengravers.com>
To: "Alberto Panizzo" <maramaopercheseimorto@gmail.com>,
       <linux-input@vger.kernel.org>
Cc: "linux-kernel" <linux-kernel@vger.kernel.org>,
       "Dmitry Torokhov" <dmitry.torokhov@gmail.com>,
       "linux-arm-kernel-infradead" <linux-arm-kernel@lists.infradead.org>,
       "Sascha linux-arm" <s.hauer@pengutronix.de>
Sender: linux-kernel-owner@vger.kernel.org
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Content-Length: 19725
Lines: 620

On Friday, January 08, 2010 11:58 AM, Alberto Panizzo wrote:
> The MXC family of Application Processors is shipped with a
> Keypad Port supported now by this driver.
> 
> The peripheral can control up to an 8x8 matrix key pad where
> all the scanning procedure is done via software. 
> 
> The hardware provide two interrupts: one for a key pressed (KDI)
> and one for all key releases (KRI). There is also a simple circuit for glitch 
> reduction (said for synchronization) made by two series of 3 D-latches
> that stabilize the interrupts sources.
> KDI and KRI are fired only if the respective conditions are maintained for 
> at last 4 keypad-clock cycle.
> 
> Those simple synchronization circuits are used also for multiple
> key pressures: between a KDI and a KRI the driver reset the 
> sync circuit and re-enable the KDI interrupt so after 3
> keypad-clock cycle another KDI is fired making possible to repeat
> the matrix scan operation.
> 
> This algorithm is done via a threaded management of the keypad
> interrupt source and delayed by a proper (and longer) debounce
> interval controlled by the platform initialization.
> If a key is pressed for a lot of time, the driver relaxes a bit
> the timings to not over load the cpu in a long time keypad interaction.
> 
> Key configuration is done via platform initialization in 
> a standard matrix_keypad manner.
> 
> This driver is tested for build in kernel or as a module
> and follow the specification of freescale i.MX 25 27 31 35 51
> especially it is tested in the mx31pdk board.
> 

You might consider using some of the matrix_keypad support already in
the kernel.  Specific's below.

> 
> Signed-off-by: Alberto Panizzo <maramaopercheseimorto@gmail.com>
> ---
>  arch/arm/plat-mxc/include/mach/mxc_keypad.h |   20 ++
>  drivers/input/keyboard/Kconfig              |    9 +
>  drivers/input/keyboard/Makefile             |    1 +
>  drivers/input/keyboard/mxc_keypad.c         |  485 +++++++++++++++++++++++++++
>  4 files changed, 515 insertions(+), 0 deletions(-)
>  create mode 100644 arch/arm/plat-mxc/include/mach/mxc_keypad.h
>  create mode 100644 drivers/input/keyboard/mxc_keypad.c
> 
> diff --git a/arch/arm/plat-mxc/include/mach/mxc_keypad.h b/arch/arm/plat-mxc/include/mach/mxc_keypad.h
> new file mode 100644
> index 0000000..1b05093
> --- /dev/null
> +++ b/arch/arm/plat-mxc/include/mach/mxc_keypad.h
> @@ -0,0 +1,20 @@
> +#ifndef __MACH_MXC_KEYPAD_H
> +#define __MACH_MXC_KEYPAD_H
> +
> +#define MAX_MATRIX_KEY_ROWS	(8)
> +#define MAX_MATRIX_KEY_COLS	(8)
> +#define MATRIX_ROW_SHIFT	(3)
> +
> +struct mxc_keypad_platform_data {
> +
> +	/* code map for the matrix keys */
> +	unsigned int	matrix_key_rows;
> +	unsigned int	matrix_key_cols;
> +	unsigned int	*matrix_key_map;
> +	int		matrix_key_map_size;
> +
> +	/* key debounce interval */
> +	unsigned int	debounce_ms;
> +};

You could use struct matrix_keymap_data to hold your matrix_key_map and
matrix_key_map_size.  Take a look at include/linux/input/matrix_keypad.h.

> +
> +#endif /* __MACH_MXC_KEYPAD_H */
> diff --git a/drivers/input/keyboard/Kconfig b/drivers/input/keyboard/Kconfig
> index ee98b1b..eff32fe 100644
> --- a/drivers/input/keyboard/Kconfig
> +++ b/drivers/input/keyboard/Kconfig
> @@ -282,6 +282,15 @@ config KEYBOARD_MAX7359
>  	  To compile this driver as a module, choose M here: the
>  	  module will be called max7359_keypad.
>  
> +config KEYBOARD_MXC
> +	tristate "MXC keypad support"
> +	depends on ARCH_MXC
> +	help
> +	  Enable support for MXC keypad port.
> +
> +	  To compile this driver as a module, choose M here: the
> +	  module will be called mxc_keypad.
> +
>  config KEYBOARD_NEWTON
>  	tristate "Newton keyboard"
>  	select SERIO
> diff --git a/drivers/input/keyboard/Makefile b/drivers/input/keyboard/Makefile
> index babad5e..9c7133a 100644
> --- a/drivers/input/keyboard/Makefile
> +++ b/drivers/input/keyboard/Makefile
> @@ -23,6 +23,7 @@ obj-$(CONFIG_KEYBOARD_LOCOMO)		+= locomokbd.o
>  obj-$(CONFIG_KEYBOARD_MAPLE)		+= maple_keyb.o
>  obj-$(CONFIG_KEYBOARD_MATRIX)		+= matrix_keypad.o
>  obj-$(CONFIG_KEYBOARD_MAX7359)		+= max7359_keypad.o
> +obj-$(CONFIG_KEYBOARD_MXC)		+= mxc_keypad.o
>  obj-$(CONFIG_KEYBOARD_NEWTON)		+= newtonkbd.o
>  obj-$(CONFIG_KEYBOARD_OMAP)		+= omap-keypad.o
>  obj-$(CONFIG_KEYBOARD_OPENCORES)	+= opencores-kbd.o
> diff --git a/drivers/input/keyboard/mxc_keypad.c b/drivers/input/keyboard/mxc_keypad.c
> new file mode 100644
> index 0000000..4acd311
> --- /dev/null
> +++ b/drivers/input/keyboard/mxc_keypad.c
> @@ -0,0 +1,485 @@
> +/*
> + * linux/drivers/input/keyboard/mxc_keypad.c
> + *
> + * Driver for the MXC keypad port.
> + * Copyright (C) 2009 Alberto Panizzo <maramaopercheseimorto@gmail.com>
> + *  based on Rodolfo Giometti & others work in pxa27x_keypad.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.
> + *
> + * >>Power management need to be implemented<<.
> + */
> +
> +#include <linux/clk.h>
> +#include <linux/delay.h>
> +#include <linux/device.h>
> +#include <linux/err.h>
> +#include <linux/init.h>
> +#include <linux/input.h>
> +#include <linux/input/matrix_keypad.h>

input.h is not needed if you are including matrix_keypad.h

> +#include <linux/interrupt.h>
> +#include <linux/io.h>
> +#include <linux/kernel.h>
> +#include <linux/module.h>
> +#include <linux/platform_device.h>
> +
> +#include <mach/mxc_keypad.h>
> +
> +/*
> + * Keypad Controller registers (halfword)
> + */
> +#define KPCR		0x00 /* Keypad Control Register */
> +
> +#define KPSR		0x02 /* Keypad Status Register */
> +#define KBD_STAT_KPKD	(0x1 << 0) /* Key Press Interrupt Status bit */
> +#define KBD_STAT_KPKR	(0x1 << 1) /* Key Release Interrupt Status bit */
> +#define KBD_STAT_KDSC	(0x1 << 2) /* Key Depress Synch Chain Status bit */
> +#define KBD_STAT_KRSS	(0x1 << 3) /* Key Release Synch Status bit */
> +#define KBD_STAT_KDIE	(0x1 << 8) /* Key Depress Interrupt Enable Status bit */
> +#define KBD_STAT_KRIE	(0x1 << 9) /* Key Release Interrupt Enable */
> +#define KBD_STAT_KPPEN	(0x1 << 10) /* Keypad Clock Enable */
> +
> +#define KDDR		0x04 /* Keypad Data Direction Register */
> +#define KPDR		0x06 /* Keypad Data Register */
> +
> +#define keypad_readw(off)	__raw_readw(keypad->mmio_base + (off))
> +#define keypad_writew(off, v)	__raw_writew((v), keypad->mmio_base + (off))

Please make the above macros inline functions.
See Documentation/CodingStyle, Chapter 12.

> +
> +#define MAX_MATRIX_KEY_NUM	(MAX_MATRIX_KEY_ROWS * MAX_MATRIX_KEY_COLS)
> +
> +struct mxc_keypad {
> +	struct mxc_keypad_platform_data *pdata;
> +
> +	struct clk *clk;
> +	struct input_dev *input_dev;
> +	void __iomem *mmio_base;
> +
> +	int			irq;
> +
> +#define MXC_IRQ_DEPRESS		1
> +#define MXC_IRQ_RELEASE		2
> +	unsigned int		irq_type;
> +
> +	int 			irq_since_last_change;
> +
> +	unsigned short 		keycodes[MAX_MATRIX_KEY_NUM];
> +
> +	/* state row bits of each column scan */
> +	unsigned short 		matrix_key_state[MAX_MATRIX_KEY_COLS];
> +};
> +
> +static void mxc_keypad_build_keycode(struct mxc_keypad *keypad)
> +{
> +	struct mxc_keypad_platform_data *pdata = keypad->pdata;
> +	struct input_dev *input_dev = keypad->input_dev;
> +	unsigned short keycode;
> +	int i;
> +
> +	for (i = 0; i < pdata->matrix_key_map_size; i++) {
> +		unsigned int key = pdata->matrix_key_map[i];
> +		unsigned int row = KEY_ROW(key);
> +		unsigned int col = KEY_COL(key);
> +		unsigned int scancode = MATRIX_SCAN_CODE(row, col,
> +							 MATRIX_ROW_SHIFT);
> +
> +		keycode = KEY_VAL(key);
> +		keypad->keycodes[scancode] = keycode;
> +		__set_bit(keycode, input_dev->keybit);
> +	}
> +
> +	__clear_bit(KEY_RESERVED, input_dev->keybit);
> +}

You should be able to use matrix_keypad_build_keymap() if you use
struct matrix_keymap_data as mentioned above.

> +
> +/* Return 0 if no changes are detected in matrix */
> +static int mxc_keypad_scan_matrix(struct mxc_keypad *keypad)
> +{
> +	struct mxc_keypad_platform_data *pdata = keypad->pdata;
> +	struct input_dev *input_dev = keypad->input_dev;
> +	int row, col, changed = 0;
> +	unsigned short new_state[MAX_MATRIX_KEY_COLS];
> +	unsigned short reg_val;
> +
> +	memset(new_state, 0, sizeof(new_state));
> +
> +	for (col = 0; col < pdata->matrix_key_cols; col++) {
> +		/* Discharge keypad capacitance:
> +		 * 2. write 1s on column data.
> +		 * 3. configure columns as totem-pole to discharge capacitance.
> +		 * 4. configure columns as open-drain.*/
> +		reg_val = keypad_readw(KPDR);
> +		reg_val |= 0xff00;
> +		keypad_writew(KPDR, reg_val);
> +
> +		reg_val = keypad_readw(KPCR);
> +		reg_val &= ~(((1 << pdata->matrix_key_cols) - 1) << 8);
> +		keypad_writew(KPCR, reg_val);
> +
> +		udelay(2);
> +
> +		reg_val = keypad_readw(KPCR);
> +		reg_val |= ((1 << pdata->matrix_key_cols) - 1) << 8;
> +		keypad_writew(KPCR, reg_val);
> +
> +		/*
> +		 * 5. Write a single column to 0, others to 1.
> +		 * 6. Sample row inputs and save data.
> +		 * 7. Repeat steps 2 - 6 for remaining columns.
> +		 */
> +		reg_val = keypad_readw(KPDR);
> +		reg_val &= ~(1 << (8 + col));
> +		keypad_writew(KPDR, reg_val);
> +
> +		/* Delay added to avoid propagating the 0 from column to row
> +		 * when scanning. */
> +		udelay(5);
> +
> +		/* 1s in state detect a key pressure */
> +		new_state[col] = (~keypad_readw(KPDR)) & 0x00ff;
> +	}
> +
> +	/* Test the state changes */
> +	for (col = 0; col < pdata->matrix_key_cols; col++) {
> +		unsigned short bits_changed;
> +		int code;
> +
> +		bits_changed = keypad->matrix_key_state[col] ^ new_state[col];
> +		if (bits_changed == 0)
> +			continue;
> +
> +		changed = 1;
> +		for (row = 0; row < pdata->matrix_key_rows; row++) {
> +			if ((bits_changed & (1 << row)) == 0)
> +				continue;
> +
> +			code = MATRIX_SCAN_CODE(row, col, MATRIX_ROW_SHIFT);
> +			input_event(input_dev, EV_MSC, MSC_SCAN, code);
> +			input_report_key(input_dev, keypad->keycodes[code],
> +					 new_state[col] & (1 << row));
> +			dev_dbg(&input_dev->dev, "Event code: %d, val: %d",
> +					keypad->keycodes[code],
> +					new_state[col] & (1 << row));
> +		}
> +	}
> +	input_sync(input_dev);
> +	memcpy(keypad->matrix_key_state, new_state, sizeof(new_state));
> +
> +	/* Return in standby mode:
> +	 * 9. write 0s to columns */
> +	reg_val = keypad_readw(KPDR);
> +	reg_val &= 0x00ff;
> +	keypad_writew(KPDR, reg_val);
> +
> +	return changed;
> +}
> +
> +static irqreturn_t mxc_keypad_irq_handler_thread(int irq, void *dev_id)
> +{
> +	struct mxc_keypad *keypad = dev_id;
> +	struct mxc_keypad_platform_data *pdata = keypad->pdata;
> +	struct input_dev *idev = keypad->input_dev;
> +	unsigned short reg_val;
> +
> +	dev_dbg(&idev->dev, "Handling Interrupt of type %x\n",
> +						keypad->irq_type);
> +
> +	/* Wait till debounce */
> +	msleep(pdata->debounce_ms);
> +
> +	/* Do the scan routine and Keep track for how many time we got
> +	 * interrupt that make no change */
> +	if (mxc_keypad_scan_matrix(keypad))
> +		keypad->irq_since_last_change = 0;
> +	else
> +		keypad->irq_since_last_change++;
> +
> +	/* If the key is pressed since too many time, relax the update period */
> +	if (keypad->irq_since_last_change > 2)
> +		msleep(100);
> +
> +	/* 10. Clear KPKD and KPKR status bits
> +	 *     Set the KPKR sync chain and clear the KPKD sync chain */
> +	reg_val = keypad_readw(KPSR);
> +	reg_val |= KBD_STAT_KPKD | KBD_STAT_KPKR |
> +		   KBD_STAT_KDSC | KBD_STAT_KRSS;
> +	keypad_writew(KPSR, reg_val);
> +
> +	/* Re enable interrupts and clear sync reset bits.
> +	 * Next KDI is used for detect multiple pressures. */
> +	reg_val = keypad_readw(KPSR);
> +	reg_val &= ~(KBD_STAT_KDSC | KBD_STAT_KRSS);
> +	keypad_writew(KPSR, reg_val);
> +
> +	reg_val |= KBD_STAT_KDIE | KBD_STAT_KRIE;
> +	if (keypad->irq_type == MXC_IRQ_RELEASE)
> +		reg_val &= ~KBD_STAT_KRIE;
> +	keypad_writew(KPSR, reg_val);
> +
> +	return IRQ_HANDLED;
> +}
> +static irqreturn_t mxc_keypad_irq_handler(int irq, void *dev_id)
> +{
> +	struct mxc_keypad *keypad = dev_id;
> +	unsigned short reg_val;
> +
> +	/* Disable every interrupt */
> +	reg_val = keypad_readw(KPSR);
> +	reg_val &= ~(KBD_STAT_KRIE | KBD_STAT_KDIE);
> +	keypad_writew(KPSR, reg_val);
> +
> +	keypad->irq_type = reg_val & KBD_STAT_KPKD ?
> +			   MXC_IRQ_DEPRESS : MXC_IRQ_RELEASE;
> +
> +	return IRQ_WAKE_THREAD;
> +}
> +
> +static void mxc_keypad_config(struct mxc_keypad *keypad)
> +{
> +	struct mxc_keypad_platform_data *pdata = keypad->pdata;
> +	unsigned short reg_val;
> +
> +	/* Enable number of rows in keypad (KPCR[7:0])
> +	 * Configure keypad columns as open-drain (KPCR[15:8])
> +	 */
> +	reg_val = keypad_readw(KPCR);
> +	reg_val |= (1 << pdata->matrix_key_rows) - 1;		/* LSB */
> +	reg_val |= ((1 << pdata->matrix_key_cols) - 1) << 8;	/* MSB */
> +	keypad_writew(KPCR, reg_val);
> +
> +	/* Write 0's to KPDR[15:8] (Colums)*/
> +	reg_val = keypad_readw(KPDR);
> +	reg_val &= 0x00ff;
> +	keypad_writew(KPDR, reg_val);
> +
> +	/* Configure columns as output, rows as input (KDDR[15:0]) */
> +	reg_val = keypad_readw(KDDR);
> +	reg_val |= 0xff00;
> +	reg_val &= 0xff00;
> +	keypad_writew(KDDR, reg_val);
> +
> +	/* Clear Key Depress and Key Release status bit.
> +	 * Clear synchronizer chain.
> +	 * */
> +	reg_val = keypad_readw(KPSR);
> +	reg_val |= KBD_STAT_KPKR | KBD_STAT_KPKD |
> +		   KBD_STAT_KDSC | KBD_STAT_KRSS;
> +	keypad_writew(KPSR, reg_val);
> +
> +	/* Set the KDIE control bit, and clear the KRIE control bit
> +	 * (avoid false release events). */
> +	reg_val |= KBD_STAT_KDIE;
> +	reg_val &= ~KBD_STAT_KRIE;
> +	keypad_writew(KPSR, reg_val);
> +}
> +
> +static void mxc_keypad_inhibit(struct mxc_keypad *keypad)
> +{
> +	unsigned short reg_val;
> +
> +	/* Colums as open drain and disable rows */
> +	keypad_writew(KPCR, 0xff00);
> +
> +	/* Clear the KPKD status flag and synchronizer chain.
> +	 * Clear KDIE control bit and KRIE control bit.
> +	 */
> +	reg_val = keypad_readw(KPSR);
> +	reg_val |= KBD_STAT_KPKD | KBD_STAT_KDSC;
> +	reg_val &= ~(KBD_STAT_KRIE | KBD_STAT_KDIE);
> +	keypad_writew(KPSR, reg_val);
> +}
> +
> +static int mxc_keypad_open(struct input_dev *dev)
> +{
> +	struct mxc_keypad *keypad = input_get_drvdata(dev);
> +	struct mxc_keypad_platform_data *pdata = keypad->pdata;
> +
> +	dev_dbg(&dev->dev, "%s\n", __func__);
> +
> +	/* Enable unit clock */
> +	clk_enable(keypad->clk);
> +	mxc_keypad_config(keypad);
> +
> +	/* Sanity control, not all the rows must be to 0s now. */
> +	if ((keypad_readw(KPDR) & ((1 << pdata->matrix_key_rows) - 1)) == 0) {
> +		dev_err(&dev->dev, "Too much keys pressed for now. "
> +				"Control pins initialisation.\n");
> +		goto open_err;
> +	}
> +
> +	return 0;
> +
> +open_err:
> +	mxc_keypad_inhibit(keypad);
> +	return -EIO;
> +}
> +
> +static void mxc_keypad_close(struct input_dev *dev)
> +{
> +	struct mxc_keypad *keypad = input_get_drvdata(dev);
> +
> +	mxc_keypad_inhibit(keypad);
> +
> +	/* Disable clock unit */
> +	clk_disable(keypad->clk);
> +}
> +
> +static int __devinit mxc_keypad_probe(struct platform_device *pdev)
> +{
> +	struct mxc_keypad_platform_data *pdata = pdev->dev.platform_data;
> +	struct mxc_keypad *keypad;
> +	struct input_dev *input_dev;
> +	struct resource *res;
> +	int irq, error;
> +
> +	if (pdata == NULL) {
> +		dev_err(&pdev->dev, "no platform data defined\n");
> +		return -EINVAL;
> +	}
> +
> +	irq = platform_get_irq(pdev, 0);
> +	if (irq < 0) {
> +		dev_err(&pdev->dev, "failed to get keypad irq\n");
> +		return -ENXIO;
> +	}
> +
> +	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
> +	if (res == NULL) {
> +		dev_err(&pdev->dev, "failed to get I/O memory\n");
> +		return -ENXIO;
> +	}
> +
> +	keypad = kzalloc(sizeof(struct mxc_keypad), GFP_KERNEL);
> +	input_dev = input_allocate_device();
> +	if (!keypad || !input_dev) {
> +		dev_err(&pdev->dev, "failed to allocate memory\n");
> +		error = -ENOMEM;
> +		goto failed_free;
> +	}
> +
> +	keypad->pdata = pdata;
> +	keypad->input_dev = input_dev;
> +	keypad->irq = irq;
> +
> +	res = request_mem_region(res->start, resource_size(res), pdev->name);
> +	if (res == NULL) {
> +		dev_err(&pdev->dev, "failed to request I/O memory\n");
> +		error = -EBUSY;
> +		goto failed_free;
> +	}
> +
> +	keypad->mmio_base = ioremap(res->start, resource_size(res));
> +	if (keypad->mmio_base == NULL) {
> +		dev_err(&pdev->dev, "failed to remap I/O memory\n");
> +		error = -ENXIO;
> +		goto failed_free_mem;
> +	}
> +
> +	keypad->clk = clk_get(NULL, "kpp");
> +	if (IS_ERR(keypad->clk)) {
> +		dev_err(&pdev->dev, "failed to get keypad clock\n");
> +		error = PTR_ERR(keypad->clk);
> +		goto failed_free_io;
> +	}
> +
> +	input_dev->name = pdev->name;
> +	input_dev->id.bustype = BUS_HOST;
> +	input_dev->open = mxc_keypad_open;
> +	input_dev->close = mxc_keypad_close;
> +	input_dev->dev.parent = &pdev->dev;
> +
> +	input_dev->keycode = keypad->keycodes;
> +	input_dev->keycodesize = sizeof(keypad->keycodes[0]);
> +	input_dev->keycodemax = ARRAY_SIZE(keypad->keycodes);
> +
> +	input_set_drvdata(input_dev, keypad);
> +
> +	input_dev->evbit[0] = BIT_MASK(EV_KEY) | BIT_MASK(EV_REP);
> +	input_set_capability(input_dev, EV_MSC, MSC_SCAN);
> +
> +	mxc_keypad_build_keycode(keypad);
> +
> +	error = request_threaded_irq(irq, mxc_keypad_irq_handler,
> +			mxc_keypad_irq_handler_thread, IRQF_DISABLED,
> +			pdev->name, keypad);
> +	if (error) {
> +		dev_err(&pdev->dev, "failed to request IRQ\n");
> +		goto failed_put_clk;
> +	}
> +
> +	/* Register the input device */
> +	error = input_register_device(input_dev);
> +	if (error) {
> +		dev_err(&pdev->dev, "failed to register input device\n");
> +		goto failed_free_irq;
> +	}
> +
> +	platform_set_drvdata(pdev, keypad);
> +	device_init_wakeup(&pdev->dev, 1);
> +
> +	dev_info(&pdev->dev, "device probed.\n");
> +
> +	return 0;
> +
> +failed_free_irq:
> +	free_irq(irq, pdev);
> +failed_put_clk:
> +	clk_put(keypad->clk);
> +failed_free_io:
> +	iounmap(keypad->mmio_base);
> +failed_free_mem:
> +	release_mem_region(res->start, resource_size(res));
> +failed_free:
> +	input_free_device(input_dev);
> +	kfree(keypad);
> +	return error;
> +}
> +
> +static int __devexit mxc_keypad_remove(struct platform_device *pdev)
> +{
> +	struct mxc_keypad *keypad = platform_get_drvdata(pdev);
> +	struct resource *res;
> +
> +	free_irq(keypad->irq, keypad);

You might want to move the platform_set_drvdata(pdev, NULL) to prevent
any race conditions.

> +	clk_put(keypad->clk);
> +
> +	input_unregister_device(keypad->input_dev);
> +	input_free_device(keypad->input_dev);

input_free_device is unnecessary for already registered devices.

> +
> +	iounmap(keypad->mmio_base);
> +
> +	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
> +	release_mem_region(res->start, resource_size(res));
> +
> +	platform_set_drvdata(pdev, NULL);
> +	kfree(keypad);
> +
> +	return 0;
> +}
> +
> +static struct platform_driver mxc_keypad_driver = {
> +	.driver		= {
> +		.name	= "mxc-keypad",
> +		.owner	= THIS_MODULE,
> +	},
> +	.probe		= mxc_keypad_probe,
> +	.remove		= __devexit_p(mxc_keypad_remove),
> +};
> +
> +static int __init mxc_keypad_init(void)
> +{
> +	return platform_driver_register(&mxc_keypad_driver);
> +}
> +
> +static void __exit mxc_keypad_exit(void)
> +{
> +	platform_driver_unregister(&mxc_keypad_driver);
> +}
> +
> +module_init(mxc_keypad_init);
> +module_exit(mxc_keypad_exit);
> +
> +MODULE_AUTHOR("Alberto Panizzo <maramaopercheseimorto@gmail.com>");
> +MODULE_DESCRIPTION("MXC Keypad Port Driver");
> +MODULE_LICENSE("GPL v2");
> +MODULE_ALIAS("platform:mxc-keypad");
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