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


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