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 <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>

1 files 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[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;