From e7e11d8ba807d451857b5c68abe249c7fc2b980f Mon Sep 17 00:00:00 2001 From: Alexander Stein Date: Tue, 29 May 2012 15:07:30 -0700 Subject: [PATCH] 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: Alexander Stein Cc: Richard Purdie Cc: Bryan Wu Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- drivers/leds/leds-pca955x.c | 95 +++++++++++++++++++++++-------------- 1 file changed, 59 insertions(+), 36 deletions(-) diff --git a/drivers/leds/leds-pca955x.c b/drivers/leds/leds-pca955x.c index dcc3bc3d38db..5f462dbf0dbb 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 */ @@ -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", - 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_led->led_cdev.name = pca955x_led->name; + pca955x_led->led_cdev.brightness_set = pca955x_led_set; - pca955x[i].led_cdev.name = pca955x[i].name; - pca955x[i].led_cdev.brightness_set = pca955x_led_set; + INIT_WORK(&pca955x_led->work, pca955x_led_work); - INIT_WORK(&pca955x[i].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;