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

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Date:   Tue, 27 Oct 2020 17:40:45 +0100
From:   Jacek Anaszewski <jacek.anaszewski@...il.com>
To:     Pavel Machek <pavel@....cz>, cy_huang <u0084500@...il.com>
Cc:     dmurphy@...com, robh+dt@...nel.org, linux-leds@...r.kernel.org,
        linux-kernel@...r.kernel.org, cy_huang@...htek.com,
        devicetree@...r.kernel.org
Subject: Re: [PATCH v1 1/2] leds: rt4505: Add support for Richtek RT4505 flash
 led controller

Hi Pavel, ChiYuan,

On 10/27/20 9:29 AM, Pavel Machek wrote:
> Hi!
> 
>> From: ChiYuan Huang <cy_huang@...htek.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@...htek.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.

-- 
Best regards,
Jacek Anaszewski