[PATCH] leds-pca955x: Fix race condition while setting brightness on several LEDs

[PATCH] leds-pca955x: Fix race condition while setting brightness on several LEDs

[Alexander Stein]

When issuing the following command:
for I in 0 1 2 3 4 5 6 7; do
  echo 0 > /sys/class/leds/pca955x\:${I}/brightness;
done
It is possible that all the pca955x_read_ls calls are done sequentially
before any pca955x_write_ls call is done. This updates the LS only to the
last LED update in its set.
Fix this by using a global lock for the pca995x device during
pca955x_led_work. Also used a struct for shared data bewteen all LEDs.

Signed-off-by: Alexander Stein <alexander.stein@systec-electronic.com>
---
 drivers/leds/leds-pca955x.c |  105 ++++++++++++++++++++++++++-----------------
 1 files changed, 64 insertions(+), 41 deletions(-)

diff --git a/drivers/leds/leds-pca955x.c b/drivers/leds/leds-pca955x.c
index dcc3bc3..2980d8e 100644
--- a/drivers/leds/leds-pca955x.c
+++ b/drivers/leds/leds-pca955x.c
@@ -101,11 +101,16 @@ static const struct i2c_device_id pca955x_id[] = {
 };
 MODULE_DEVICE_TABLE(i2c, pca955x_id);
 
-struct pca955x_led {
+struct pca955x {
+	struct mutex lock;
+	struct pca955x_led *leds;
 	struct pca955x_chipdef	*chipdef;
 	struct i2c_client	*client;
+};
+
+struct pca955x_led {
+	struct pca955x	*pca955x;
 	struct work_struct	work;
-	spinlock_t		lock;
 	enum led_brightness	brightness;
 	struct led_classdev	led_cdev;
 	int			led_num;	/* 0 .. 15 potentially */
@@ -128,7 +133,7 @@ static inline int pca95xx_num_led_regs(int bits)
  * Return an LED selector register value based on an existing one, with
  * the appropriate 2-bit state value set for the given LED number (0-3).
  */
-static inline u8 pca955x_ledsel(u8 oldval, int led_num, int state)
+static inline u8 pca955x_ledel(u8 oldval, int led_num, int state)
 {
 	return (oldval & (~(0x3 << (led_num << 1)))) |
 		((state & 0x3) << (led_num << 1));
@@ -140,7 +145,7 @@ static inline u8 pca955x_ledsel(u8 oldval, int led_num, int state)
  */
 static void pca955x_write_psc(struct i2c_client *client, int n, u8 val)
 {
-	struct pca955x_led *pca955x = i2c_get_clientdata(client);
+	struct pca955x *pca955x = i2c_get_clientdata(client);
 
 	i2c_smbus_write_byte_data(client,
 		pca95xx_num_input_regs(pca955x->chipdef->bits) + 2*n,
@@ -156,7 +161,7 @@ static void pca955x_write_psc(struct i2c_client *client, int n, u8 val)
  */
 static void pca955x_write_pwm(struct i2c_client *client, int n, u8 val)
 {
-	struct pca955x_led *pca955x = i2c_get_clientdata(client);
+	struct pca955x *pca955x = i2c_get_clientdata(client);
 
 	i2c_smbus_write_byte_data(client,
 		pca95xx_num_input_regs(pca955x->chipdef->bits) + 1 + 2*n,
@@ -169,7 +174,7 @@ static void pca955x_write_pwm(struct i2c_client *client, int n, u8 val)
  */
 static void pca955x_write_ls(struct i2c_client *client, int n, u8 val)
 {
-	struct pca955x_led *pca955x = i2c_get_clientdata(client);
+	struct pca955x *pca955x = i2c_get_clientdata(client);
 
 	i2c_smbus_write_byte_data(client,
 		pca95xx_num_input_regs(pca955x->chipdef->bits) + 4 + n,
@@ -182,7 +187,7 @@ static void pca955x_write_ls(struct i2c_client *client, int n, u8 val)
  */
 static u8 pca955x_read_ls(struct i2c_client *client, int n)
 {
-	struct pca955x_led *pca955x = i2c_get_clientdata(client);
+	struct pca955x *pca955x = i2c_get_clientdata(client);
 
 	return (u8) i2c_smbus_read_byte_data(client,
 		pca95xx_num_input_regs(pca955x->chipdef->bits) + 4 + n);
@@ -190,26 +195,31 @@ static u8 pca955x_read_ls(struct i2c_client *client, int n)
 
 static void pca955x_led_work(struct work_struct *work)
 {
-	struct pca955x_led *pca955x;
+	struct pca955x_led *pca955x_led;
+	struct pca955x *pca955x;
 	u8 ls;
 	int chip_ls;	/* which LSx to use (0-3 potentially) */
 	int ls_led;	/* which set of bits within LSx to use (0-3) */
 
-	pca955x = container_of(work, struct pca955x_led, work);
-	chip_ls = pca955x->led_num / 4;
-	ls_led = pca955x->led_num % 4;
+	pca955x_led = container_of(work, struct pca955x_led, work);
+	pca955x = pca955x_led->pca955x;
+
+	chip_ls = pca955x_led->led_num / 4;
+	ls_led = pca955x_led->led_num % 4;
+
+	mutex_lock(&pca955x->lock);
 
 	ls = pca955x_read_ls(pca955x->client, chip_ls);
 
-	switch (pca955x->brightness) {
+	switch (pca955x_led->brightness) {
 	case LED_FULL:
-		ls = pca955x_ledsel(ls, ls_led, PCA955X_LS_LED_ON);
+		ls = pca955x_ledel(ls, ls_led, PCA955X_LS_LED_ON);
 		break;
 	case LED_OFF:
-		ls = pca955x_ledsel(ls, ls_led, PCA955X_LS_LED_OFF);
+		ls = pca955x_ledel(ls, ls_led, PCA955X_LS_LED_OFF);
 		break;
 	case LED_HALF:
-		ls = pca955x_ledsel(ls, ls_led, PCA955X_LS_BLINK0);
+		ls = pca955x_ledel(ls, ls_led, PCA955X_LS_BLINK0);
 		break;
 	default:
 		/*
@@ -219,12 +229,15 @@ static void pca955x_led_work(struct work_struct *work)
 		 * OFF, HALF, or FULL.  But, this is probably better than
 		 * just turning off for all other values.
 		 */
-		pca955x_write_pwm(pca955x->client, 1, 255-pca955x->brightness);
-		ls = pca955x_ledsel(ls, ls_led, PCA955X_LS_BLINK1);
+		pca955x_write_pwm(pca955x->client, 1,
+				255 - pca955x_led->brightness);
+		ls = pca955x_ledel(ls, ls_led, PCA955X_LS_BLINK1);
 		break;
 	}
 
 	pca955x_write_ls(pca955x->client, chip_ls, ls);
+
+	mutex_unlock(&pca955x->lock);
 }
 
 static void pca955x_led_set(struct led_classdev *led_cdev, enum led_brightness value)
@@ -233,7 +246,6 @@ static void pca955x_led_set(struct led_classdev *led_cdev, enum led_brightness v
 
 	pca955x = container_of(led_cdev, struct pca955x_led, led_cdev);
 
-	spin_lock(&pca955x->lock);
 	pca955x->brightness = value;
 
 	/*
@@ -241,14 +253,13 @@ static void pca955x_led_set(struct led_classdev *led_cdev, enum led_brightness v
 	 * can sleep.
 	 */
 	schedule_work(&pca955x->work);
-
-	spin_unlock(&pca955x->lock);
 }
 
 static int __devinit pca955x_probe(struct i2c_client *client,
 					const struct i2c_device_id *id)
 {
-	struct pca955x_led *pca955x;
+	struct pca955x *pca955x;
+	struct pca955x_led *pca955x_led;
 	struct pca955x_chipdef *chip;
 	struct i2c_adapter *adapter;
 	struct led_platform_data *pdata;
@@ -282,39 +293,48 @@ static int __devinit pca955x_probe(struct i2c_client *client,
 		}
 	}
 
-	pca955x = kzalloc(sizeof(*pca955x) * chip->bits, GFP_KERNEL);
+	pca955x = kzalloc(sizeof(*pca955x), GFP_KERNEL);
 	if (!pca955x)
 		return -ENOMEM;
 
+	pca955x->leds = kzalloc(sizeof(*pca955x_led) * chip->bits, GFP_KERNEL);
+	if (!pca955x->leds) {
+		err = -ENOMEM;
+		goto exit_nomem;
+	}
+
 	i2c_set_clientdata(client, pca955x);
 
+	mutex_init(&pca955x->lock);
+	pca955x->client = client;
+	pca955x->chipdef = chip;
+
 	for (i = 0; i < chip->bits; i++) {
-		pca955x[i].chipdef = chip;
-		pca955x[i].client = client;
-		pca955x[i].led_num = i;
+		pca955x_led = &pca955x->leds[i];
+		pca955x_led->led_num = i;
+		pca955x_led->pca955x = pca955x;
 
 		/* Platform data can specify LED names and default triggers */
 		if (pdata) {
 			if (pdata->leds[i].name)
-				snprintf(pca955x[i].name,
-					 sizeof(pca955x[i].name), "pca955x:%s",
-					 pdata->leds[i].name);
+				snprintf(pca955x_led->name,
+					sizeof(pca955x_led->name), "pca955x:%s",
+					pdata->leds[i].name);
 			if (pdata->leds[i].default_trigger)
-				pca955x[i].led_cdev.default_trigger =
+				pca955x_led->led_cdev.default_trigger =
 					pdata->leds[i].default_trigger;
 		} else {
-			snprintf(pca955x[i].name, sizeof(pca955x[i].name),
+			snprintf(pca955x_led->name, sizeof(pca955x_led->name),
 				 "pca955x:%d", i);
 		}
 
-		spin_lock_init(&pca955x[i].lock);
-
-		pca955x[i].led_cdev.name = pca955x[i].name;
-		pca955x[i].led_cdev.brightness_set = pca955x_led_set;
+		pca955x_led->led_cdev.name = pca955x_led->name;
+		pca955x_led->led_cdev.brightness_set = pca955x_led_set;
 
-		INIT_WORK(&pca955x[i].work, pca955x_led_work);
+		INIT_WORK(&pca955x_led->work, pca955x_led_work);
 
-		err = led_classdev_register(&client->dev, &pca955x[i].led_cdev);
+		err = led_classdev_register(&client->dev,
+					&pca955x_led->led_cdev);
 		if (err < 0)
 			goto exit;
 	}
@@ -337,10 +357,12 @@ static int __devinit pca955x_probe(struct i2c_client *client,
 
 exit:
 	while (i--) {
-		led_classdev_unregister(&pca955x[i].led_cdev);
-		cancel_work_sync(&pca955x[i].work);
+		led_classdev_unregister(&pca955x->leds[i].led_cdev);
+		cancel_work_sync(&pca955x->leds[i].work);
 	}
 
+	kfree(pca955x->leds);
+exit_nomem:
 	kfree(pca955x);
 
 	return err;
@@ -348,14 +370,15 @@ exit:
 
 static int __devexit pca955x_remove(struct i2c_client *client)
 {
-	struct pca955x_led *pca955x = i2c_get_clientdata(client);
+	struct pca955x *pca955x = i2c_get_clientdata(client);
 	int i;
 
 	for (i = 0; i < pca955x->chipdef->bits; i++) {
-		led_classdev_unregister(&pca955x[i].led_cdev);
-		cancel_work_sync(&pca955x[i].work);
+		led_classdev_unregister(&pca955x->leds[i].led_cdev);
+		cancel_work_sync(&pca955x->leds[i].work);
 	}
 
+	kfree(pca955x->leds);
 	kfree(pca955x);
 
 	return 0;
-- 
1.7.3.4

Re: [PATCH] leds-pca955x: Fix race condition while setting brightness on several LEDs

[Alexander Stein]

Any news/feedback on this?

Regards,
Alexander

Am Mittwoch, 8. Februar 2012, 13:44:08 schrieb Alexander Stein:
> When issuing the following command:
> for I in 0 1 2 3 4 5 6 7; do
>   echo 0 > /sys/class/leds/pca955x\:${I}/brightness;
> done
> It is possible that all the pca955x_read_ls calls are done sequentially
> before any pca955x_write_ls call is done. This updates the LS only to the
> last LED update in its set.
> Fix this by using a global lock for the pca995x device during
> pca955x_led_work. Also used a struct for shared data bewteen all LEDs.
> 
> Signed-off-by: Alexander Stein <alexander.stein@systec-electronic.com>
> ---
>  drivers/leds/leds-pca955x.c |  105
> ++++++++++++++++++++++++++----------------- 1 files changed, 64
> insertions(+), 41 deletions(-)
> 
> diff --git a/drivers/leds/leds-pca955x.c b/drivers/leds/leds-pca955x.c
> index dcc3bc3..2980d8e 100644
> --- a/drivers/leds/leds-pca955x.c
> +++ b/drivers/leds/leds-pca955x.c
> @@ -101,11 +101,16 @@ static const struct i2c_device_id pca955x_id[] = {
>  };
>  MODULE_DEVICE_TABLE(i2c, pca955x_id);
> 
> -struct pca955x_led {
> +struct pca955x {
> +	struct mutex lock;
> +	struct pca955x_led *leds;
>  	struct pca955x_chipdef	*chipdef;
>  	struct i2c_client	*client;
> +};
> +
> +struct pca955x_led {
> +	struct pca955x	*pca955x;
>  	struct work_struct	work;
> -	spinlock_t		lock;
>  	enum led_brightness	brightness;
>  	struct led_classdev	led_cdev;
>  	int			led_num;	/* 0 .. 15 potentially */
> @@ -128,7 +133,7 @@ static inline int pca95xx_num_led_regs(int bits)
>   * Return an LED selector register value based on an existing one, with
>   * the appropriate 2-bit state value set for the given LED number (0-3).
>   */
> -static inline u8 pca955x_ledsel(u8 oldval, int led_num, int state)
> +static inline u8 pca955x_ledel(u8 oldval, int led_num, int state)
>  {
>  	return (oldval & (~(0x3 << (led_num << 1)))) |
>  		((state & 0x3) << (led_num << 1));
> @@ -140,7 +145,7 @@ static inline u8 pca955x_ledsel(u8 oldval, int led_num,
> int state) */
>  static void pca955x_write_psc(struct i2c_client *client, int n, u8 val)
>  {
> -	struct pca955x_led *pca955x = i2c_get_clientdata(client);
> +	struct pca955x *pca955x = i2c_get_clientdata(client);
> 
>  	i2c_smbus_write_byte_data(client,
>  		pca95xx_num_input_regs(pca955x->chipdef->bits) + 2*n,
> @@ -156,7 +161,7 @@ static void pca955x_write_psc(struct i2c_client *client,
> int n, u8 val) */
>  static void pca955x_write_pwm(struct i2c_client *client, int n, u8 val)
>  {
> -	struct pca955x_led *pca955x = i2c_get_clientdata(client);
> +	struct pca955x *pca955x = i2c_get_clientdata(client);
> 
>  	i2c_smbus_write_byte_data(client,
>  		pca95xx_num_input_regs(pca955x->chipdef->bits) + 1 + 2*n,
> @@ -169,7 +174,7 @@ static void pca955x_write_pwm(struct i2c_client *client,
> int n, u8 val) */
>  static void pca955x_write_ls(struct i2c_client *client, int n, u8 val)
>  {
> -	struct pca955x_led *pca955x = i2c_get_clientdata(client);
> +	struct pca955x *pca955x = i2c_get_clientdata(client);
> 
>  	i2c_smbus_write_byte_data(client,
>  		pca95xx_num_input_regs(pca955x->chipdef->bits) + 4 + n,
> @@ -182,7 +187,7 @@ static void pca955x_write_ls(struct i2c_client *client,
> int n, u8 val) */
>  static u8 pca955x_read_ls(struct i2c_client *client, int n)
>  {
> -	struct pca955x_led *pca955x = i2c_get_clientdata(client);
> +	struct pca955x *pca955x = i2c_get_clientdata(client);
> 
>  	return (u8) i2c_smbus_read_byte_data(client,
>  		pca95xx_num_input_regs(pca955x->chipdef->bits) + 4 + n);
> @@ -190,26 +195,31 @@ static u8 pca955x_read_ls(struct i2c_client *client,
> int n)
> 
>  static void pca955x_led_work(struct work_struct *work)
>  {
> -	struct pca955x_led *pca955x;
> +	struct pca955x_led *pca955x_led;
> +	struct pca955x *pca955x;
>  	u8 ls;
>  	int chip_ls;	/* which LSx to use (0-3 potentially) */
>  	int ls_led;	/* which set of bits within LSx to use (0-3) */
> 
> -	pca955x = container_of(work, struct pca955x_led, work);
> -	chip_ls = pca955x->led_num / 4;
> -	ls_led = pca955x->led_num % 4;
> +	pca955x_led = container_of(work, struct pca955x_led, work);
> +	pca955x = pca955x_led->pca955x;
> +
> +	chip_ls = pca955x_led->led_num / 4;
> +	ls_led = pca955x_led->led_num % 4;
> +
> +	mutex_lock(&pca955x->lock);
> 
>  	ls = pca955x_read_ls(pca955x->client, chip_ls);
> 
> -	switch (pca955x->brightness) {
> +	switch (pca955x_led->brightness) {
>  	case LED_FULL:
> -		ls = pca955x_ledsel(ls, ls_led, PCA955X_LS_LED_ON);
> +		ls = pca955x_ledel(ls, ls_led, PCA955X_LS_LED_ON);
>  		break;
>  	case LED_OFF:
> -		ls = pca955x_ledsel(ls, ls_led, PCA955X_LS_LED_OFF);
> +		ls = pca955x_ledel(ls, ls_led, PCA955X_LS_LED_OFF);
>  		break;
>  	case LED_HALF:
> -		ls = pca955x_ledsel(ls, ls_led, PCA955X_LS_BLINK0);
> +		ls = pca955x_ledel(ls, ls_led, PCA955X_LS_BLINK0);
>  		break;
>  	default:
>  		/*
> @@ -219,12 +229,15 @@ static void pca955x_led_work(struct work_struct *work)
> * OFF, HALF, or FULL.  But, this is probably better than
>  		 * just turning off for all other values.
>  		 */
> -		pca955x_write_pwm(pca955x->client, 1, 255-pca955x->brightness);
> -		ls = pca955x_ledsel(ls, ls_led, PCA955X_LS_BLINK1);
> +		pca955x_write_pwm(pca955x->client, 1,
> +				255 - pca955x_led->brightness);
> +		ls = pca955x_ledel(ls, ls_led, PCA955X_LS_BLINK1);
>  		break;
>  	}
> 
>  	pca955x_write_ls(pca955x->client, chip_ls, ls);
> +
> +	mutex_unlock(&pca955x->lock);
>  }
> 
>  static void pca955x_led_set(struct led_classdev *led_cdev, enum
> led_brightness value) @@ -233,7 +246,6 @@ static void
> pca955x_led_set(struct led_classdev *led_cdev, enum led_brightness v
> 
>  	pca955x = container_of(led_cdev, struct pca955x_led, led_cdev);
> 
> -	spin_lock(&pca955x->lock);
>  	pca955x->brightness = value;
> 
>  	/*
> @@ -241,14 +253,13 @@ static void pca955x_led_set(struct led_classdev
> *led_cdev, enum led_brightness v * can sleep.
>  	 */
>  	schedule_work(&pca955x->work);
> -
> -	spin_unlock(&pca955x->lock);
>  }
> 
>  static int __devinit pca955x_probe(struct i2c_client *client,
>  					const struct i2c_device_id *id)
>  {
> -	struct pca955x_led *pca955x;
> +	struct pca955x *pca955x;
> +	struct pca955x_led *pca955x_led;
>  	struct pca955x_chipdef *chip;
>  	struct i2c_adapter *adapter;
>  	struct led_platform_data *pdata;
> @@ -282,39 +293,48 @@ static int __devinit pca955x_probe(struct i2c_client
> *client, }
>  	}
> 
> -	pca955x = kzalloc(sizeof(*pca955x) * chip->bits, GFP_KERNEL);
> +	pca955x = kzalloc(sizeof(*pca955x), GFP_KERNEL);
>  	if (!pca955x)
>  		return -ENOMEM;
> 
> +	pca955x->leds = kzalloc(sizeof(*pca955x_led) * chip->bits, GFP_KERNEL);
> +	if (!pca955x->leds) {
> +		err = -ENOMEM;
> +		goto exit_nomem;
> +	}
> +
>  	i2c_set_clientdata(client, pca955x);
> 
> +	mutex_init(&pca955x->lock);
> +	pca955x->client = client;
> +	pca955x->chipdef = chip;
> +
>  	for (i = 0; i < chip->bits; i++) {
> -		pca955x[i].chipdef = chip;
> -		pca955x[i].client = client;
> -		pca955x[i].led_num = i;
> +		pca955x_led = &pca955x->leds[i];
> +		pca955x_led->led_num = i;
> +		pca955x_led->pca955x = pca955x;
> 
>  		/* Platform data can specify LED names and default triggers */
>  		if (pdata) {
>  			if (pdata->leds[i].name)
> -				snprintf(pca955x[i].name,
> -					 sizeof(pca955x[i].name), "pca955x:%s",
> -					 pdata->leds[i].name);
> +				snprintf(pca955x_led->name,
> +					sizeof(pca955x_led->name), "pca955x:%s",
> +					pdata->leds[i].name);
>  			if (pdata->leds[i].default_trigger)
> -				pca955x[i].led_cdev.default_trigger =
> +				pca955x_led->led_cdev.default_trigger =
>  					pdata->leds[i].default_trigger;
>  		} else {
> -			snprintf(pca955x[i].name, sizeof(pca955x[i].name),
> +			snprintf(pca955x_led->name, sizeof(pca955x_led->name),
>  				 "pca955x:%d", i);
>  		}
> 
> -		spin_lock_init(&pca955x[i].lock);
> -
> -		pca955x[i].led_cdev.name = pca955x[i].name;
> -		pca955x[i].led_cdev.brightness_set = pca955x_led_set;
> +		pca955x_led->led_cdev.name = pca955x_led->name;
> +		pca955x_led->led_cdev.brightness_set = pca955x_led_set;
> 
> -		INIT_WORK(&pca955x[i].work, pca955x_led_work);
> +		INIT_WORK(&pca955x_led->work, pca955x_led_work);
> 
> -		err = led_classdev_register(&client->dev, &pca955x[i].led_cdev);
> +		err = led_classdev_register(&client->dev,
> +					&pca955x_led->led_cdev);
>  		if (err < 0)
>  			goto exit;
>  	}
> @@ -337,10 +357,12 @@ static int __devinit pca955x_probe(struct i2c_client
> *client,
> 
>  exit:
>  	while (i--) {
> -		led_classdev_unregister(&pca955x[i].led_cdev);
> -		cancel_work_sync(&pca955x[i].work);
> +		led_classdev_unregister(&pca955x->leds[i].led_cdev);
> +		cancel_work_sync(&pca955x->leds[i].work);
>  	}
> 
> +	kfree(pca955x->leds);
> +exit_nomem:
>  	kfree(pca955x);
> 
>  	return err;
> @@ -348,14 +370,15 @@ exit:
> 
>  static int __devexit pca955x_remove(struct i2c_client *client)
>  {
> -	struct pca955x_led *pca955x = i2c_get_clientdata(client);
> +	struct pca955x *pca955x = i2c_get_clientdata(client);
>  	int i;
> 
>  	for (i = 0; i < pca955x->chipdef->bits; i++) {
> -		led_classdev_unregister(&pca955x[i].led_cdev);
> -		cancel_work_sync(&pca955x[i].work);
> +		led_classdev_unregister(&pca955x->leds[i].led_cdev);
> +		cancel_work_sync(&pca955x->leds[i].work);
>  	}
> 
> +	kfree(pca955x->leds);
>  	kfree(pca955x);
> 
>  	return 0;
-- 
Dipl.-Inf. Alexander Stein

SYS TEC electronic GmbH
August-Bebel-Str. 29
D-07973 Greiz

Tel: +49-3661-6279-0, Fax: +49-3661-6279-99
eMail:    Alexander.Stein@systec-electronic.com
Internet: http://www.systec-electronic.com

Managing Director: Dipl.-Phys. Siegmar Schmidt
Commercial registry: Amtsgericht Jena, HRB 205563

Re: [PATCH] leds-pca955x: Fix race condition while setting brightness on several LEDs

[Alexander Stein]

Any news/feedback on this?

Regards,
Alexander

On Tuesday 20 March 2012 14:03:11, Alexander Stein wrote:
> Any news/feedback on this?
> 
> Regards,
> Alexander
> 
> Am Mittwoch, 8. Februar 2012, 13:44:08 schrieb Alexander Stein:
> > When issuing the following command:
> > for I in 0 1 2 3 4 5 6 7; do
> > 
> >   echo 0 > /sys/class/leds/pca955x\:${I}/brightness;
> > 
> > done
> > It is possible that all the pca955x_read_ls calls are done sequentially
> > before any pca955x_write_ls call is done. This updates the LS only to the
> > last LED update in its set.
> > Fix this by using a global lock for the pca995x device during
> > pca955x_led_work. Also used a struct for shared data bewteen all LEDs.
> > 
> > Signed-off-by: Alexander Stein <alexander.stein@systec-electronic.com>
> > ---
> > 
> >  drivers/leds/leds-pca955x.c |  105
> > 
> > ++++++++++++++++++++++++++----------------- 1 files changed, 64
> > insertions(+), 41 deletions(-)
> > 
> > diff --git a/drivers/leds/leds-pca955x.c b/drivers/leds/leds-pca955x.c
> > index dcc3bc3..2980d8e 100644
> > --- a/drivers/leds/leds-pca955x.c
> > +++ b/drivers/leds/leds-pca955x.c
> > @@ -101,11 +101,16 @@ static const struct i2c_device_id pca955x_id[] = {
> > 
> >  };
> >  MODULE_DEVICE_TABLE(i2c, pca955x_id);
> > 
> > -struct pca955x_led {
> > +struct pca955x {
> > +	struct mutex lock;
> > +	struct pca955x_led *leds;
> > 
> >  	struct pca955x_chipdef	*chipdef;
> >  	struct i2c_client	*client;
> > 
> > +};
> > +
> > +struct pca955x_led {
> > +	struct pca955x	*pca955x;
> > 
> >  	struct work_struct	work;
> > 
> > -	spinlock_t		lock;
> > 
> >  	enum led_brightness	brightness;
> >  	struct led_classdev	led_cdev;
> >  	int			led_num;	/* 0 .. 15 potentially */
> > 
> > @@ -128,7 +133,7 @@ static inline int pca95xx_num_led_regs(int bits)
> > 
> >   * Return an LED selector register value based on an existing one, with
> >   * the appropriate 2-bit state value set for the given LED number (0-3).
> >   */
> > 
> > -static inline u8 pca955x_ledsel(u8 oldval, int led_num, int state)
> > +static inline u8 pca955x_ledel(u8 oldval, int led_num, int state)
> > 
> >  {
> >  
> >  	return (oldval & (~(0x3 << (led_num << 1)))) |
> >  	
> >  		((state & 0x3) << (led_num << 1));
> > 
> > @@ -140,7 +145,7 @@ static inline u8 pca955x_ledsel(u8 oldval, int
> > led_num,
> > int state) */
> > 
> >  static void pca955x_write_psc(struct i2c_client *client, int n, u8 val)
> >  {
> > 
> > -	struct pca955x_led *pca955x = i2c_get_clientdata(client);
> > +	struct pca955x *pca955x = i2c_get_clientdata(client);
> > 
> >  	i2c_smbus_write_byte_data(client,
> >  	
> >  		pca95xx_num_input_regs(pca955x->chipdef->bits) + 2*n,
> > 
> > @@ -156,7 +161,7 @@ static void pca955x_write_psc(struct i2c_client
> > *client, int n, u8 val) */
> > 
> >  static void pca955x_write_pwm(struct i2c_client *client, int n, u8 val)
> >  {
> > 
> > -	struct pca955x_led *pca955x = i2c_get_clientdata(client);
> > +	struct pca955x *pca955x = i2c_get_clientdata(client);
> > 
> >  	i2c_smbus_write_byte_data(client,
> >  	
> >  		pca95xx_num_input_regs(pca955x->chipdef->bits) + 1 + 2*n,
> > 
> > @@ -169,7 +174,7 @@ static void pca955x_write_pwm(struct i2c_client
> > *client, int n, u8 val) */
> > 
> >  static void pca955x_write_ls(struct i2c_client *client, int n, u8 val)
> >  {
> > 
> > -	struct pca955x_led *pca955x = i2c_get_clientdata(client);
> > +	struct pca955x *pca955x = i2c_get_clientdata(client);
> > 
> >  	i2c_smbus_write_byte_data(client,
> >  	
> >  		pca95xx_num_input_regs(pca955x->chipdef->bits) + 4 + n,
> > 
> > @@ -182,7 +187,7 @@ static void pca955x_write_ls(struct i2c_client
> > *client,
> > int n, u8 val) */
> > 
> >  static u8 pca955x_read_ls(struct i2c_client *client, int n)
> >  {
> > 
> > -	struct pca955x_led *pca955x = i2c_get_clientdata(client);
> > +	struct pca955x *pca955x = i2c_get_clientdata(client);
> > 
> >  	return (u8) i2c_smbus_read_byte_data(client,
> >  	
> >  		pca95xx_num_input_regs(pca955x->chipdef->bits) + 4 + n);
> > 
> > @@ -190,26 +195,31 @@ static u8 pca955x_read_ls(struct i2c_client *client,
> > int n)
> > 
> >  static void pca955x_led_work(struct work_struct *work)
> >  {
> > 
> > -	struct pca955x_led *pca955x;
> > +	struct pca955x_led *pca955x_led;
> > +	struct pca955x *pca955x;
> > 
> >  	u8 ls;
> >  	int chip_ls;	/* which LSx to use (0-3 potentially) */
> >  	int ls_led;	/* which set of bits within LSx to use (0-3) */
> > 
> > -	pca955x = container_of(work, struct pca955x_led, work);
> > -	chip_ls = pca955x->led_num / 4;
> > -	ls_led = pca955x->led_num % 4;
> > +	pca955x_led = container_of(work, struct pca955x_led, work);
> > +	pca955x = pca955x_led->pca955x;
> > +
> > +	chip_ls = pca955x_led->led_num / 4;
> > +	ls_led = pca955x_led->led_num % 4;
> > +
> > +	mutex_lock(&pca955x->lock);
> > 
> >  	ls = pca955x_read_ls(pca955x->client, chip_ls);
> > 
> > -	switch (pca955x->brightness) {
> > +	switch (pca955x_led->brightness) {
> > 
> >  	case LED_FULL:
> > -		ls = pca955x_ledsel(ls, ls_led, PCA955X_LS_LED_ON);
> > +		ls = pca955x_ledel(ls, ls_led, PCA955X_LS_LED_ON);
> > 
> >  		break;
> >  	
> >  	case LED_OFF:
> > -		ls = pca955x_ledsel(ls, ls_led, PCA955X_LS_LED_OFF);
> > +		ls = pca955x_ledel(ls, ls_led, PCA955X_LS_LED_OFF);
> > 
> >  		break;
> >  	
> >  	case LED_HALF:
> > -		ls = pca955x_ledsel(ls, ls_led, PCA955X_LS_BLINK0);
> > +		ls = pca955x_ledel(ls, ls_led, PCA955X_LS_BLINK0);
> > 
> >  		break;
> >  	
> >  	default:
> >  		/*
> > 
> > @@ -219,12 +229,15 @@ static void pca955x_led_work(struct work_struct
> > *work) * OFF, HALF, or FULL.  But, this is probably better than
> > 
> >  		 * just turning off for all other values.
> >  		 */
> > 
> > -		pca955x_write_pwm(pca955x->client, 1, 255-pca955x->brightness);
> > -		ls = pca955x_ledsel(ls, ls_led, PCA955X_LS_BLINK1);
> > +		pca955x_write_pwm(pca955x->client, 1,
> > +				255 - pca955x_led->brightness);
> > +		ls = pca955x_ledel(ls, ls_led, PCA955X_LS_BLINK1);
> > 
> >  		break;
> >  	
> >  	}
> >  	
> >  	pca955x_write_ls(pca955x->client, chip_ls, ls);
> > 
> > +
> > +	mutex_unlock(&pca955x->lock);
> > 
> >  }
> >  
> >  static void pca955x_led_set(struct led_classdev *led_cdev, enum
> > 
> > led_brightness value) @@ -233,7 +246,6 @@ static void
> > pca955x_led_set(struct led_classdev *led_cdev, enum led_brightness v
> > 
> >  	pca955x = container_of(led_cdev, struct pca955x_led, led_cdev);
> > 
> > -	spin_lock(&pca955x->lock);
> > 
> >  	pca955x->brightness = value;
> >  	
> >  	/*
> > 
> > @@ -241,14 +253,13 @@ static void pca955x_led_set(struct led_classdev
> > *led_cdev, enum led_brightness v * can sleep.
> > 
> >  	 */
> >  	
> >  	schedule_work(&pca955x->work);
> > 
> > -
> > -	spin_unlock(&pca955x->lock);
> > 
> >  }
> >  
> >  static int __devinit pca955x_probe(struct i2c_client *client,
> >  
> >  					const struct i2c_device_id *id)
> >  
> >  {
> > 
> > -	struct pca955x_led *pca955x;
> > +	struct pca955x *pca955x;
> > +	struct pca955x_led *pca955x_led;
> > 
> >  	struct pca955x_chipdef *chip;
> >  	struct i2c_adapter *adapter;
> >  	struct led_platform_data *pdata;
> > 
> > @@ -282,39 +293,48 @@ static int __devinit pca955x_probe(struct i2c_client
> > *client, }
> > 
> >  	}
> > 
> > -	pca955x = kzalloc(sizeof(*pca955x) * chip->bits, GFP_KERNEL);
> > +	pca955x = kzalloc(sizeof(*pca955x), GFP_KERNEL);
> > 
> >  	if (!pca955x)
> >  	
> >  		return -ENOMEM;
> > 
> > +	pca955x->leds = kzalloc(sizeof(*pca955x_led) * chip->bits, 
GFP_KERNEL);
> > +	if (!pca955x->leds) {
> > +		err = -ENOMEM;
> > +		goto exit_nomem;
> > +	}
> > +
> > 
> >  	i2c_set_clientdata(client, pca955x);
> > 
> > +	mutex_init(&pca955x->lock);
> > +	pca955x->client = client;
> > +	pca955x->chipdef = chip;
> > +
> > 
> >  	for (i = 0; i < chip->bits; i++) {
> > 
> > -		pca955x[i].chipdef = chip;
> > -		pca955x[i].client = client;
> > -		pca955x[i].led_num = i;
> > +		pca955x_led = &pca955x->leds[i];
> > +		pca955x_led->led_num = i;
> > +		pca955x_led->pca955x = pca955x;
> > 
> >  		/* Platform data can specify LED names and default triggers */
> >  		if (pdata) {
> >  		
> >  			if (pdata->leds[i].name)
> > 
> > -				snprintf(pca955x[i].name,
> > -					 sizeof(pca955x[i].name), "pca955x:%s",
> > -					 pdata->leds[i].name);
> > +				snprintf(pca955x_led->name,
> > +					sizeof(pca955x_led->name), "pca955x:%s",
> > +					pdata->leds[i].name);
> > 
> >  			if (pdata->leds[i].default_trigger)
> > 
> > -				pca955x[i].led_cdev.default_trigger =
> > +				pca955x_led->led_cdev.default_trigger =
> > 
> >  					pdata->leds[i].default_trigger;
> >  		
> >  		} else {
> > 
> > -			snprintf(pca955x[i].name, sizeof(pca955x[i].name),
> > +			snprintf(pca955x_led->name, sizeof(pca955x_led->name),
> > 
> >  				 "pca955x:%d", i);
> >  		
> >  		}
> > 
> > -		spin_lock_init(&pca955x[i].lock);
> > -
> > -		pca955x[i].led_cdev.name = pca955x[i].name;
> > -		pca955x[i].led_cdev.brightness_set = pca955x_led_set;
> > +		pca955x_led->led_cdev.name = pca955x_led->name;
> > +		pca955x_led->led_cdev.brightness_set = pca955x_led_set;
> > 
> > -		INIT_WORK(&pca955x[i].work, pca955x_led_work);
> > +		INIT_WORK(&pca955x_led->work, pca955x_led_work);
> > 
> > -		err = led_classdev_register(&client->dev, &pca955x[i].led_cdev);
> > +		err = led_classdev_register(&client->dev,
> > +					&pca955x_led->led_cdev);
> > 
> >  		if (err < 0)
> >  		
> >  			goto exit;
> >  	
> >  	}
> > 
> > @@ -337,10 +357,12 @@ static int __devinit pca955x_probe(struct i2c_client
> > *client,
> > 
> >  exit:
> >  	while (i--) {
> > 
> > -		led_classdev_unregister(&pca955x[i].led_cdev);
> > -		cancel_work_sync(&pca955x[i].work);
> > +		led_classdev_unregister(&pca955x->leds[i].led_cdev);
> > +		cancel_work_sync(&pca955x->leds[i].work);
> > 
> >  	}
> > 
> > +	kfree(pca955x->leds);
> > 
> > +exit_nomem:
> >  	kfree(pca955x);
> >  	
> >  	return err;
> > 
> > @@ -348,14 +370,15 @@ exit:
> >  static int __devexit pca955x_remove(struct i2c_client *client)
> >  {
> > 
> > -	struct pca955x_led *pca955x = i2c_get_clientdata(client);
> > +	struct pca955x *pca955x = i2c_get_clientdata(client);
> > 
> >  	int i;
> >  	
> >  	for (i = 0; i < pca955x->chipdef->bits; i++) {
> > 
> > -		led_classdev_unregister(&pca955x[i].led_cdev);
> > -		cancel_work_sync(&pca955x[i].work);
> > +		led_classdev_unregister(&pca955x->leds[i].led_cdev);
> > +		cancel_work_sync(&pca955x->leds[i].work);
> > 
> >  	}
> > 
> > +	kfree(pca955x->leds);
> > 
> >  	kfree(pca955x);
> >  	
> >  	return 0;
-- 
Dipl.-Inf. Alexander Stein

SYS TEC electronic GmbH
August-Bebel-Str. 29
D-07973 Greiz

Tel: +49-3661-6279-0, Fax: +49-3661-6279-99
eMail:    Alexander.Stein@systec-electronic.com
Internet: http://www.systec-electronic.com

Managing Director: Dipl.-Phys. Siegmar Schmidt
Commercial registry: Amtsgericht Jena, HRB 205563

Re: [PATCH] leds-pca955x: Fix race condition while setting brightness on several LEDs

[Andrew Morton]

On Wed,  8 Feb 2012 13:44:08 +0100
Alexander Stein <alexander.stein@systec-electronic.com> wrote:

> When issuing the following command:
> for I in 0 1 2 3 4 5 6 7; do
>   echo 0 > /sys/class/leds/pca955x\:${I}/brightness;
> done
> It is possible that all the pca955x_read_ls calls are done sequentially
> before any pca955x_write_ls call is done. This updates the LS only to the
> last LED update in its set.
> Fix this by using a global lock for the pca995x device during
> pca955x_led_work.

There's the bugfix.

> Also used a struct for shared data bewteen all LEDs.

And there's an apparently unrelated change whcih created a *lot* of
noise in the patch.  It would be good to separate these things, with
the bugfix being the first change.

> ...
>
> -static inline u8 pca955x_ledsel(u8 oldval, int led_num, int state)
> +static inline u8 pca955x_ledel(u8 oldval, int led_num, int state)

Why was this function renamed, and what does "ledel" mean?

Re: [PATCH] leds-pca955x: Fix race condition while setting brightness on several LEDs

[Alexander Stein]

Am Donnerstag, 10. Mai 2012, 14:40:16 schrieb Andrew Morton:
> On Wed,  8 Feb 2012 13:44:08 +0100
> 
> Alexander Stein <alexander.stein@systec-electronic.com> wrote:
> > When issuing the following command:
> > for I in 0 1 2 3 4 5 6 7; do
> > 
> >   echo 0 > /sys/class/leds/pca955x\:${I}/brightness;
> > 
> > done
> > It is possible that all the pca955x_read_ls calls are done sequentially
> > before any pca955x_write_ls call is done. This updates the LS only to the
> > last LED update in its set.
> > Fix this by using a global lock for the pca995x device during
> > pca955x_led_work.
> 
> There's the bugfix.
> 
> > Also used a struct for shared data bewteen all LEDs.
> 
> And there's an apparently unrelated change whcih created a *lot* of
> noise in the patch.  It would be good to separate these things, with
> the bugfix being the first change.

This doesn't work. A problem was that each LED had it's own lock used upon 
scheduling it's own workqueue. No synchronization betwen all LEDs on this 
chip.

> > ...
> > 
> > -static inline u8 pca955x_ledsel(u8 oldval, int led_num, int state)
> > +static inline u8 pca955x_ledel(u8 oldval, int led_num, int state)
> 
> Why was this function renamed, and what does "ledel" mean?

Whoops, my mistake. This wasn't intended. I will gladly send a new patch with 
the last function name change reverted. Unless someone objects against the 
synchronizaton.

Regards,
Alexander
-- 
Dipl.-Inf. Alexander Stein

SYS TEC electronic GmbH
August-Bebel-Str. 29
D-07973 Greiz

Tel: +49-3661-6279-0, Fax: +49-3661-6279-99
eMail:    Alexander.Stein@systec-electronic.com
Internet: http://www.systec-electronic.com

Managing Director: Dipl.-Phys. Siegmar Schmidt
Commercial registry: Amtsgericht Jena, HRB 205563