Date:	Sat, 7 Mar 2009 22:38:43 -0800
From:	Dmitry Torokhov <dmitry.torokhov@...il.com>
To:	Bryan Wu <cooloney@...nel.org>,
	Michael Hennerich <michael.hennerich@...log.com>
Cc:	akpm@...ux-foundation.org, linux-input@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/1] Input/Touchscreen Driver: add support AD7877
	touchscreen driver (try #5)

Hi Bryan, Michael,

On Fri, Oct 17, 2008 at 01:56:08AM +0800, Bryan Wu wrote:
> From: Michael Hennerich <michael.hennerich@...log.com>
> 
> [try #5]
>  - Fix indention
>  - Lock spi_async()
>  - Remove useless header comments
>  - Use strict_strtoul
>  - Use EDGE triggered interrupts ?\226?\128?\147 this simplifies some of the IRQ handling.
>  - Fix error cleanup path
>  - Remove duplicated code
>  - SPI access functions parameter use struct spi_device
> 

I looked at the latest version of the driver in Andrew's queue and I
think it needs the following changes:

- you can't have parts of bitfield updated from IRQ context and part from
  process context unless every field is protected by the same spinlock.

- You need more full mutual exclusion between enable and disable so you
  don't inadvertingly kill the timer if you disable and enable from
  different processes.

- I think you need serialization in various store() methods so that
  consistent values are written into chip's registers.

- There were coule of inverted logic errors in disabling chip code.

- Kay is trying to get rid of bus_id in devices, you need to use
  dev_name() instead.

Could you please try the patch below and let me know if the driver still
works so I can commit it. I also did some formatting changes, I hope you
don't mind. Thanks!

-- 
Dmitry

Input: ad7877 fixups

Signed-off-by: Dmitry Torokhov <dtor@...l.ru>
---

 drivers/input/touchscreen/ad7877.c |  226 ++++++++++++++++--------------------
 1 files changed, 99 insertions(+), 127 deletions(-)


diff --git a/drivers/input/touchscreen/ad7877.c b/drivers/input/touchscreen/ad7877.c
index 6615bcd..6702364 100644
--- a/drivers/input/touchscreen/ad7877.c
+++ b/drivers/input/touchscreen/ad7877.c
@@ -1,7 +1,7 @@
 /*
  * File:        drivers/input/touchscreen/ad7877.c
  *
- * Based on: 	ads7846.c
+ * Based on:	ads7846.c
  *
  *		Copyright (C) 2006-2008 Michael Hennerich, Analog Devices Inc.
  *
@@ -185,21 +185,24 @@ struct ad7877 {
 	u8			averaging;
 	u8			pen_down_acc_interval;
 
-	u16 			conversion_data[AD7877_NR_SENSE];
+	u16			conversion_data[AD7877_NR_SENSE];
 
 	struct spi_transfer	xfer[AD7877_NR_SENSE + 2];
 	struct spi_message	msg;
 
+	struct mutex		mutex;
+	unsigned		disabled:1;	/* P: mutex */
+	unsigned		gpio3:1;	/* P: mutex */
+	unsigned		gpio4:1;	/* P: mutex */
+
 	spinlock_t		lock;
 	struct timer_list	timer;		/* P: lock */
-	unsigned		pendown:1;	/* P: lock */
 	unsigned		pending:1;	/* P: lock */
-	unsigned		disabled:1;
-	unsigned		gpio3:1;
-	unsigned		gpio4:1;
 };
 
 static int gpio3;
+module_param(gpio3, int, 0);
+MODULE_PARM_DESC(gpio3, "If gpio3 is set to 1 AUX3 acts as GPIO3");
 
 /*
  * ad7877_read/write are only used for initial setup and for sysfs controls.
@@ -208,9 +211,10 @@ static int gpio3;
 
 static int ad7877_read(struct spi_device *spi, u16 reg)
 {
-	struct ser_req		*req = kzalloc(sizeof *req, GFP_KERNEL);
-	int			status, ret;
+	struct ser_req *req;
+	int status, ret;
 
+	req = kzalloc(sizeof *req, GFP_KERNEL);
 	if (!req)
 		return -ENOMEM;
 
@@ -228,11 +232,8 @@ static int ad7877_read(struct spi_device *spi, u16 reg)
 	spi_message_add_tail(&req->xfer[1], &req->msg);
 
 	status = spi_sync(spi, &req->msg);
+	ret = status ? : req->sample;
 
-	if (status == 0)
-		status = req->msg.status;
-
-	ret = status ? status : req->sample;
 	kfree(req);
 
 	return ret;
@@ -240,9 +241,10 @@ static int ad7877_read(struct spi_device *spi, u16 reg)
 
 static int ad7877_write(struct spi_device *spi, u16 reg, u16 val)
 {
-	struct ser_req		*req = kzalloc(sizeof *req, GFP_KERNEL);
-	int			status;
+	struct ser_req *req;
+	int status;
 
+	req = kzalloc(sizeof *req, GFP_KERNEL);
 	if (!req)
 		return -ENOMEM;
 
@@ -256,9 +258,6 @@ static int ad7877_write(struct spi_device *spi, u16 reg, u16 val)
 
 	status = spi_sync(spi, &req->msg);
 
-	if (status == 0)
-		status = req->msg.status;
-
 	kfree(req);
 
 	return status;
@@ -266,12 +265,13 @@ static int ad7877_write(struct spi_device *spi, u16 reg, u16 val)
 
 static int ad7877_read_adc(struct spi_device *spi, unsigned command)
 {
-	struct ad7877 		*ts = dev_get_drvdata(&spi->dev);
-	struct ser_req		*req = kzalloc(sizeof *req, GFP_KERNEL);
-	int			status;
-	int			sample;
-	int			i;
+	struct ad7877 *ts = dev_get_drvdata(&spi->dev);
+	struct ser_req *req;
+	int status;
+	int sample;
+	int i;
 
+	req = kzalloc(sizeof *req, GFP_KERNEL);
 	if (!req)
 		return -ENOMEM;
 
@@ -314,21 +314,18 @@ static int ad7877_read_adc(struct spi_device *spi, unsigned command)
 		spi_message_add_tail(&req->xfer[i], &req->msg);
 
 	status = spi_sync(spi, &req->msg);
-
-	if (status == 0)
-		status = req->msg.status;
-
 	sample = req->sample;
 
 	kfree(req);
-	return status ? status : sample;
+
+	return status ? : sample;
 }
 
 static void ad7877_rx(struct ad7877 *ts)
 {
-	struct input_dev	*input_dev = ts->input;
-	unsigned		Rt;
-	u16			x, y, z1, z2;
+	struct input_dev *input_dev = ts->input;
+	unsigned Rt;
+	u16 x, y, z1, z2;
 
 	x = ts->conversion_data[AD7877_SEQ_XPOS] & MAX_12BIT;
 	y = ts->conversion_data[AD7877_SEQ_YPOS] & MAX_12BIT;
@@ -350,10 +347,7 @@ static void ad7877_rx(struct ad7877 *ts)
 		Rt = (z2 - z1) * x * ts->x_plate_ohms;
 		Rt /= z1;
 		Rt = (Rt + 2047) >> 12;
-	} else
-		Rt = 0;
 
-	if (Rt) {
 		input_report_abs(input_dev, ABS_X, x);
 		input_report_abs(input_dev, ABS_Y, y);
 		input_report_abs(input_dev, ABS_PRESSURE, Rt);
@@ -371,7 +365,7 @@ static inline void ad7877_ts_event_release(struct ad7877 *ts)
 
 static void ad7877_timer(unsigned long handle)
 {
-	struct ad7877	*ts = (void *)handle;
+	struct ad7877 *ts = (void *)handle;
 
 	ad7877_ts_event_release(ts);
 }
@@ -382,78 +376,72 @@ static irqreturn_t ad7877_irq(int irq, void *handle)
 	unsigned long flags;
 	int status;
 
-	/* The repeated conversion sequencer controlled by TMR kicked off too fast.
-	 * We ignore the last and process the sample sequence currently in the queue
-	 * It can't be older than 9.4ms, and we need to avoid that ts->msg
-	 * doesn't get issued twice while in work.
+	/*
+	 * The repeated conversion sequencer controlled by TMR kicked off
+	 * too fast. We ignore the last and process the sample sequence
+	 * currently in the queue. It can't be older than 9.4ms, and we
+	 * need to avoid that ts->msg doesn't get issued twice while in work.
 	 */
 
 	spin_lock_irqsave(&ts->lock, flags);
-	if (ts->pending) {
-		spin_unlock_irqrestore(&ts->lock, flags);
-		return IRQ_HANDLED;
+	if (!ts->pending) {
+		ts->pending = 1;
+
+		status = spi_async(ts->spi, &ts->msg);
+		if (status)
+			dev_err(&ts->spi->dev, "spi_sync --> %d\n", status);
 	}
-	ts->pending = 1;
 	spin_unlock_irqrestore(&ts->lock, flags);
 
-	status = spi_async(ts->spi, &ts->msg);
-
-	if (status)
-		dev_err(&ts->spi->dev, "spi_sync --> %d\n", status);
-
 	return IRQ_HANDLED;
 }
 
 static void ad7877_callback(void *_ts)
 {
 	struct ad7877 *ts = _ts;
-	unsigned long flags;
 
-	ad7877_rx(ts);
+	spin_lock_irq(&ts->lock);
 
-	spin_lock_irqsave(&ts->lock, flags);
+	ad7877_rx(ts);
 	ts->pending = 0;
 	mod_timer(&ts->timer, jiffies + TS_PEN_UP_TIMEOUT);
-	spin_unlock_irqrestore(&ts->lock, flags);
+
+	spin_unlock_irq(&ts->lock);
 }
 
 static void ad7877_disable(struct ad7877 *ts)
 {
-	unsigned long flags;
-
-	spin_lock_irqsave(&ts->lock, flags);
-	if (ts->disabled) {
-		spin_unlock_irqrestore(&ts->lock, flags);
-		return;
-	}
+	mutex_lock(&ts->mutex);
 
-	ts->disabled = 1;
-	disable_irq(ts->spi->irq);
-	spin_unlock_irqrestore(&ts->lock, flags);
+	if (!ts->disabled) {
+		ts->disabled = 1;
+		disable_irq(ts->spi->irq);
 
-	while (ts->pending) /* Wait for spi_async callback */
-		msleep(1);
+		/* Wait for spi_async callback */
+		while (ts->pending)
+			msleep(1);
 
-	if (del_timer_sync(&ts->timer))
-		ad7877_ts_event_release(ts);
+		if (del_timer_sync(&ts->timer))
+			ad7877_ts_event_release(ts);
+	}
 
 	/* we know the chip's in lowpower mode since we always
 	 * leave it that way after every request
 	 */
+
+	mutex_unlock(&ts->mutex);
 }
 
 static void ad7877_enable(struct ad7877 *ts)
 {
-	unsigned long flags;
+	mutex_lock(&ts->mutex);
 
-	spin_lock_irqsave(&ts->lock, flags);
 	if (ts->disabled) {
-		spin_unlock_irqrestore(&ts->lock, flags);
-		return;
+		ts->disabled = 0;
+		enable_irq(ts->spi->irq);
 	}
-	ts->disabled = 0;
-	enable_irq(ts->spi->irq);
-	spin_unlock_irqrestore(&ts->lock, flags);
+
+	mutex_unlock(&ts->mutex);
 }
 
 #define SHOW(name) static ssize_t \
@@ -490,12 +478,11 @@ static ssize_t ad7877_disable_store(struct device *dev,
 {
 	struct ad7877 *ts = dev_get_drvdata(dev);
 	unsigned long val;
-	int ret;
+	int error;
 
-	ret = strict_strtoul(buf, 10, &val);
-
-	if (ret)
-		return ret;
+	error = strict_strtoul(buf, 10, &val);
+	if (error)
+		return error;
 
 	if (val)
 		ad7877_disable(ts);
@@ -521,16 +508,16 @@ static ssize_t ad7877_dac_store(struct device *dev,
 {
 	struct ad7877 *ts = dev_get_drvdata(dev);
 	unsigned long val;
-	int ret;
-
-	ret = strict_strtoul(buf, 10, &val);
+	int error;
 
-	if (ret)
-		return ret;
+	error = strict_strtoul(buf, 10, &val);
+	if (error)
+		return error;
 
+	mutex_lock(&ts->mutex);
 	ts->dac = val & 0xFF;
-
 	ad7877_write(ts->spi, AD7877_REG_DAC, (ts->dac << 4) | AD7877_DAC_CONF);
+	mutex_unlock(&ts->mutex);
 
 	return count;
 }
@@ -551,16 +538,17 @@ static ssize_t ad7877_gpio3_store(struct device *dev,
 {
 	struct ad7877 *ts = dev_get_drvdata(dev);
 	unsigned long val;
-	int ret;
+	int error;
 
-	ret = strict_strtoul(buf, 10, &val);
-	if (ret)
-		return ret;
+	error = strict_strtoul(buf, 10, &val);
+	if (error)
+		return error;
 
+	mutex_lock(&ts->mutex);
 	ts->gpio3 = !!val;
-
 	ad7877_write(ts->spi, AD7877_REG_EXTWRITE, AD7877_EXTW_GPIO_DATA |
 		 (ts->gpio4 << 4) | (ts->gpio3 << 5));
+	mutex_unlock(&ts->mutex);
 
 	return count;
 }
@@ -581,16 +569,17 @@ static ssize_t ad7877_gpio4_store(struct device *dev,
 {
 	struct ad7877 *ts = dev_get_drvdata(dev);
 	unsigned long val;
-	int ret;
+	int error;
 
-	ret = strict_strtoul(buf, 10, &val);
-	if (ret)
-		return ret;
+	error = strict_strtoul(buf, 10, &val);
+	if (error)
+		return error;
 
+	mutex_lock(&ts->mutex);
 	ts->gpio4 = !!val;
-
 	ad7877_write(ts->spi, AD7877_REG_EXTWRITE, AD7877_EXTW_GPIO_DATA |
-		 (ts->gpio4 << 4) | (ts->gpio3 << 5));
+		     (ts->gpio4 << 4) | (ts->gpio3 << 5));
+	mutex_unlock(&ts->mutex);
 
 	return count;
 }
@@ -685,14 +674,10 @@ static int __devinit ad7877_probe(struct spi_device *spi)
 	}
 
 	ts = kzalloc(sizeof(struct ad7877), GFP_KERNEL);
-	if (!ts)
-		return -ENOMEM;
-
-
 	input_dev = input_allocate_device();
-	if (!input_dev) {
-		kfree(ts);
-		return -ENOMEM;
+	if (!ts || !input_dev) {
+		err = -ENOMEM;
+		goto err_free_mem;
 	}
 
 	dev_set_drvdata(&spi->dev, ts);
@@ -700,6 +685,7 @@ static int __devinit ad7877_probe(struct spi_device *spi)
 	ts->input = input_dev;
 
 	setup_timer(&ts->timer, ad7877_timer, (unsigned long) ts);
+	mutex_init(&ts->mutex);
 	spin_lock_init(&ts->lock);
 
 	ts->model = pdata->model ? : 7877;
@@ -713,7 +699,7 @@ static int __devinit ad7877_probe(struct spi_device *spi)
 	ts->averaging = pdata->averaging;
 	ts->pen_down_acc_interval = pdata->pen_down_acc_interval;
 
-	snprintf(ts->phys, sizeof(ts->phys), "%s/inputX", spi->dev.bus_id);
+	snprintf(ts->phys, sizeof(ts->phys), "%s/input0", dev_name(&spi->dev));
 
 	input_dev->name = "AD7877 Touchscreen";
 	input_dev->phys = ts->phys;
@@ -761,30 +747,25 @@ static int __devinit ad7877_probe(struct spi_device *spi)
 	}
 
 	err = sysfs_create_group(&spi->dev.kobj, &ad7877_attr_group);
-
-	if (gpio3)
-		err |= device_create_file(&spi->dev, &dev_attr_gpio3);
-	else
-		err |= device_create_file(&spi->dev, &dev_attr_aux3);
-
 	if (err)
 		goto err_free_irq;
 
+	err = device_create_file(&spi->dev,
+				 gpio3 ? &dev_attr_gpio3 : &dev_attr_aux3);
+	if (err)
+		goto err_remove_attr_group;
+
 	err = input_register_device(input_dev);
 	if (err)
 		goto err_remove_attr;
 
-	dev_info(&spi->dev, "touchscreen, irq %d\n", spi->irq);
-
 	return 0;
 
 err_remove_attr:
+	device_remove_file(&spi->dev,
+			   gpio3 ? &dev_attr_gpio3 : &dev_attr_aux3);
+err_remove_attr_group:
 	sysfs_remove_group(&spi->dev.kobj, &ad7877_attr_group);
-
-	if (gpio3)
-		device_remove_file(&spi->dev, &dev_attr_gpio3);
-	else
-		device_remove_file(&spi->dev, &dev_attr_aux3);
 err_free_irq:
 	free_irq(spi->irq, ts);
 err_free_mem:
@@ -798,19 +779,14 @@ static int __devexit ad7877_remove(struct spi_device *spi)
 {
 	struct ad7877		*ts = dev_get_drvdata(&spi->dev);
 
-	ad7877_disable(ts);
-
 	sysfs_remove_group(&spi->dev.kobj, &ad7877_attr_group);
+	device_remove_file(&spi->dev,
+			   gpio3 ? &dev_attr_gpio3 : &dev_attr_aux3);
 
-	if (gpio3)
-		device_remove_file(&spi->dev, &dev_attr_gpio3);
-	else
-		device_remove_file(&spi->dev, &dev_attr_aux3);
-
+	ad7877_disable(ts);
 	free_irq(ts->spi->irq, ts);
 
 	input_unregister_device(ts->input);
-
 	kfree(ts);
 
 	dev_dbg(&spi->dev, "unregistered touchscreen\n");
@@ -866,10 +842,6 @@ static void __exit ad7877_exit(void)
 }
 module_exit(ad7877_exit);
 
-module_param(gpio3, int, 0);
-MODULE_PARM_DESC(gpio3,
-	"If gpio3 is set to 1 AUX3 acts as GPIO3");
-
 MODULE_AUTHOR("Michael Hennerich <hennerich@...ckfin.uclinux.org>");
 MODULE_DESCRIPTION("AD7877 touchscreen Driver");
 MODULE_LICENSE("GPL");
--
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