drivers/leds/leds-pca955x.c: fix race condition while setting brightness on several...

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 <alexander.stein@systec-electronic.com>
Cc: Richard Purdie <rpurdie@rpsys.net>
Cc: Bryan Wu <bryan.wu@canonical.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/drivers/leds/leds-pca955x.c b/drivers/leds/leds-pca955x.c
index dcc3bc3d38db8cac7384c65009965967bc026f24..5f462dbf0dbbf4920bfc281c6ad69cfc8486ed5d 100644 (file)
--- 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[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;