Messages in this thread | | | From | Alexander Stein <> | Subject | Re: [PATCH] leds-pca955x: Fix race condition while setting brightness on several LEDs | Date | Tue, 20 Mar 2012 14:03:11 +0100 |
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Any news/feedback on this?
Regards, Alexander
Am Mittwoch, 8. Februar 2012, 13:44:08 schrieb Alexander Stein: > 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; -- Dipl.-Inf. Alexander Stein
SYS TEC electronic GmbH August-Bebel-Str. 29 D-07973 Greiz
Tel: +49-3661-6279-0, Fax: +49-3661-6279-99 eMail: Alexander.Stein@systec-electronic.com Internet: http://www.systec-electronic.com
Managing Director: Dipl.-Phys. Siegmar Schmidt Commercial registry: Amtsgericht Jena, HRB 205563
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