Commit e7e11d8b authored by Alexander Stein's avatar Alexander Stein Committed by Linus Torvalds
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drivers/leds/leds-pca955x.c: fix race condition while setting brightness on several LEDs 



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 betreen all LEDs.

[akpm@linux-foundation.org: revert unintentional rename of pca955x_ledsel()]
Signed-off-by: default avatarAlexander Stein <alexander.stein@systec-electronic.com>
Cc: Richard Purdie <rpurdie@rpsys.net>
Cc: Bryan Wu <bryan.wu@canonical.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 44e1e9f8

drivers/leds/leds-pca955x.c

+59 −36
Original line number Diff line number Diff line
@@ -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 */
@@ -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);
@@ -190,18 +195,23 @@ 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);

		break;
@@ -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);

		pca955x_write_pwm(pca955x->client, 1,

				255 - pca955x_led->brightness);

		ls = pca955x_ledsel(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",

				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;

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