linux-kernel - Re: [PATCH] leds: tlc591xx: update the maximum brightness

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Date:   Mon, 14 Oct 2019 12:37:53 +0200
From:   Jean-Jacques Hiblot <jjhiblot@...com>
To:     Jacek Anaszewski <jacek.anaszewski@...il.com>,
        Pavel Machek <pavel@....cz>
CC:     <dmurphy@...com>, <linux-leds@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>, Andrew Lunn <andrew@...n.ch>
Subject: Re: [PATCH] leds: tlc591xx: update the maximum brightness


On 13/10/2019 18:36, Jacek Anaszewski wrote:
> On 10/13/19 1:45 PM, Pavel Machek wrote:
>> Hi!
>>
>>>> @@ -112,11 +113,11 @@ tlc591xx_brightness_set(struct led_classdev *led_cdev,
>>>>   	struct tlc591xx_priv *priv = led->priv;
>>>>   	int err;
>>>>   
>>>> -	switch (brightness) {
>>>> +	switch ((int)brightness) {
>>>>   	case 0:
>> Can we get a rid of the cast here? Do we need to move away from the
>> enum for the brightness?
> I at first also wanted to ask for dropping the cast but first tried
> to do it myself. Then I found out compiler (or sparse, I don't recall
> exactly) complains about TLC591XX_MAX_BRIGHTNESS not being a value of
> enum led_brighteess type. That's the reason for the cast Jean added,
> I presume.

Indeed that cast is to fix the warning.

JJ

>>> Added tag:
>>>
>>> Fixes: e370d010a5fe ("leds: tlc591xx: Driver for the TI 8/16 Channel i2c
>>> LED driver")
>>>
>>> and applied to the for-5.5 branch.
>> Actually, careful with the Fixes tag. -stable people will want to
>> apply it, and it may not be a good idea in this case. Maximum
>> brightness of 256 is pretty unusual, so I'd call this "a bit risky".
> I entirely disagree. Not seeing anything risky in that since
> max_brightness is also initialized to this value. If userspace properly
> uses the ABI, then it will be safe.
>
>> Best regards,
>> 									Pavel
>>