Messages in this thread | | | Subject | Re: [PATCH v1 1/2] leds: rt4505: Add support for Richtek RT4505 flash led controller | From | Jacek Anaszewski <> | Date | Wed, 28 Oct 2020 12:07:04 +0100 |
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On 10/28/20 5:57 AM, ChiYuan Huang wrote: > Hi, > > Jacek Anaszewski <jacek.anaszewski@gmail.com> 於 2020年10月28日 週三 上午12:40寫道: >> >> Hi Pavel, ChiYuan, >> >> On 10/27/20 9:29 AM, Pavel Machek wrote: >>> Hi! >>> >>>> From: ChiYuan Huang <cy_huang@richtek.com> >>>> >>>> Add support for RT4505 flash led controller. It can support up to 1.5A >>>> flash current with hardware timeout and low input voltage >>>> protection. >>> >>> Please use upper-case "LED" everywhere. >>> >>> This should be 2nd in the series, after DT changes. >>> >>>> Signed-off-by: ChiYuan Huang <cy_huang@richtek.com> >>>> --- >>>> drivers/leds/Kconfig | 11 ++ >>>> drivers/leds/Makefile | 1 + >>>> drivers/leds/leds-rt4505.c | 397 +++++++++++++++++++++++++++++++++++++++++++++ >>>> 3 files changed, 409 insertions(+) >>>> create mode 100644 drivers/leds/leds-rt4505.c >> [...] >>>> +static int rt4505_torch_brightness_set(struct led_classdev *lcdev, enum led_brightness level) >>>> +{ >>> >>> 80 columns, where easy. >>> >>>> + struct rt4505_priv *priv = container_of(lcdev, struct rt4505_priv, flash.led_cdev); >>>> + u32 val = 0; >>>> + int ret; >>>> + >>>> + mutex_lock(&priv->lock); >>>> + >>>> + if (level != LED_OFF) { >>>> + ret = regmap_update_bits(priv->regmap, RT4505_REG_ILED, RT4505_ITORCH_MASK, >>>> + (level - 1) << RT4505_ITORCH_SHIFT); >>>> + if (ret) >>>> + goto unlock; >>>> + >>>> + val = RT4505_TORCH_SET; >>>> + } >>>> + >>>> + ret = regmap_update_bits(priv->regmap, RT4505_REG_ENABLE, RT4505_ENABLE_MASK, val); >>>> + >>>> +unlock: >>>> + mutex_unlock(&priv->lock); >>>> + return ret; >>>> +} >>> >>> Why is the locking needed? What will the /sys/class/leds interface >>> look like on system with your flash? >> >> The locking is needed since this can be called via led_set_brightness() >> from any place in the kernel, and especially from triggers. >>From this case, It means only led classdev > brihtness_get/brightness_set need to be protected. > I search led_flash_classdev, it only can be controlled via sysfs or V4l2. > Like as described in last mail, flash related operation is protected > by led access_lock and v4l2 framework. > I'll keep the locking only in led classdev brightness_get/brightness_set API. > If I misunderstand something, please help to point out.
Locking have to be used consistently for each access to the resource being protected with the lock. Otherwise you can end up in a situation when rt4505_torch_brightness_set and rt4505_flash_brightness_set will try concurrently alter hardware state. Regardless of how harmful could it be in case of this particular device it is certainly against programming rules.
-- Best regards, Jacek Anaszewski
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