On 10/28/20 5:57 AM, ChiYuan Huang wrote:
Hi,
Jacek Anaszewski <jacek.anaszewski@xxxxxxxxx> 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@xxxxxxxxxxx>
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@xxxxxxxxxxx>
---
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
