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

From: Alexander Stein
Date: Tue May 08 2012 - 02:52:03 EST

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Any news/feedback on this?

Regards,
Alexander

On Tuesday 20 March 2012 14:03:11, Alexander Stein wrote:
> 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@xxxxxxxxxxxxxxxxxxxxx>
> > ---
> >
> > 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@xxxxxxxxxxxxxxxxxxxxx
Internet: http://www.systec-electronic.com

Managing Director: Dipl.-Phys. Siegmar Schmidt
Commercial registry: Amtsgericht Jena, HRB 205563
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Next message: Dave Airlie: "Re: [PATCH] mm: Work around Intel SNB GTT bug with some physical pages."
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