Re: [PATCH v1 1/2] leds: rt4505: Add support for Richtek RT4505 flash led controller

Hi,

Jacek Anaszewski [off-list ref] 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:

quoted

Hi!

quoted

From: ChiYuan Huang <redacted>

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.

quoted

Signed-off-by: ChiYuan Huang <redacted>
---
  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

[...]

quoted

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+static int rt4505_torch_brightness_set(struct led_classdev *lcdev, enum led_brightness level)
+{

80 columns, where easy.

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+    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.
Thx.

--
Best regards,
Jacek Anaszewski