linux-kernel - Re: [PATCH v6 2/2] leds: lm3601x: Introduce the lm3601x LED driver

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Date:   Wed, 16 May 2018 23:02:34 +0200
From:   Jacek Anaszewski <jacek.anaszewski@...il.com>
To:     Andy Shevchenko <andy.shevchenko@...il.com>,
        Dan Murphy <dmurphy@...com>
Cc:     Rob Herring <robh+dt@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Pavel Machek <pavel@....cz>,
        devicetree <devicetree@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Linux LED Subsystem <linux-leds@...r.kernel.org>
Subject: Re: [PATCH v6 2/2] leds: lm3601x: Introduce the lm3601x LED driver

Hi Andy and Dan,

On 05/16/2018 12:24 AM, Andy Shevchenko wrote:
> On Wed, May 16, 2018 at 1:08 AM, Dan Murphy <dmurphy@...com> wrote:
>> On 05/15/2018 04:56 PM, Andy Shevchenko wrote:
>>> On Tue, May 15, 2018 at 6:43 PM, Dan Murphy <dmurphy@...com> wrote:
> 
>>>> +       depends on LEDS_CLASS && I2C && OF
>>>
>>> What is OF specific in this driver?
>>
>> as3645a_led_class_setup has a "of" dependency
> 
> So what? Is it called from this driver or?
> 
> 
>>>> +static const struct lm3601x_max_timeouts strobe_timeouts[] = {
>>>> +       { 40000, 0x00 },
>>>> +       { 80000, 0x01 },
>>>> +       { 120000, 0x02 },
>>>> +       { 160000, 0x03 },
>>>> +       { 200000, 0x04 },
>>>> +       { 240000, 0x05 },
>>>> +       { 280000, 0x06 },
>>>> +       { 320000, 0x07 },
>>>> +       { 360000, 0x08 },
>>>> +       { 400000, 0x09 },
>>>> +       { 600000, 0x0a },
>>>> +       { 800000, 0x0b },
>>>> +       { 1000000, 0x0c },
>>>> +       { 1200000, 0x0d },
>>>> +       { 1400000, 0x0e },
>>>> +       { 1600000, 0x0f },
>>>
>>> Huh?!
>>
>> Please give comments that actually mean something other wise I will opt to ignore them.
> 
> I did below.
> 
>>> strobe_timeout = (x + 1) * 40 * MSECS_IN_SEC;
>>
>> Not sure what equation you are trying to point out here.  But if you are trying to apply
>> a timeout step you cannot do this with this part.  As pointed out in the DT doc the timeout
>> step is not linear.
> 
> Yeah, I know people are more than often too lazy to think.
> 
> if (x < 9)
>   strobe_timeout = (x + 1) * 40 * MSECS_IN_SEC;
> else
>   strobe_timeout = (400 + (x - 9) * 200) * MSECS_IN_SEC;
> 

I like the idea.

>>>> +               brightness_val = (brightness/2);
>>>
>>> Spaces.
>>
>> Not sure what this means checkpatch was clean
> 
> Even besides missed whispaces it has redundant parens.
> 
> checkpatch is not a silver bullet to get your code clean and nice.
> 
>>> This is return led_...();
>>
>> That is a preference.  It does not have to be that way.

I missed that. Dan, please follow Andy's advise.

> 
> What do you mean? We do not appreciate +LOCs for no (or even nagative!) benefit.
> 
>>>> +               ret = of_property_read_string(led->led_node, "label", &name);
>>>
>>> device_property_...();
>>
>> It can be if the maintainer is requesting this.
> 
> Jacek, if you need rationale behind this comment it's here: the driver
> has nothing DT specific and getting rid of OF centric programming
> allows to reuse the driver on non-DT platforms w/o touching a source
> code.

It has an added value, so yes, let's use it as a standard approach
from now on.

>> Is the trend to move to these functions?
> 
> See above.
> 
>> Most drivers use the "of" calls.
> 
> So what?
> 
> 
>>>> +               if (!ret)
>>>
>>> if (ret) sounds more natural. And better just to split
>>>
>>>> +                       snprintf(led->led_name, sizeof(led->led_name),
>>>> +                               "%s:%s", led->led_node->name, name);
>>>> +               else
>>>> +                       snprintf(led->led_name, sizeof(led->led_name),
>>>> +                               "%s:torch", led->led_node->name);
>>>
>>> const char *tmp;
>>>
>>> ret = device_property_read_...(&tmp);
>>> if (ret)
>>>   tmp = ...
>>> sprintf(...);

We're no longer taking devicename section of a LED class device name
from DT, so it will look differently anyway.

> No comments on this?
> 
>>>> +       led = devm_kzalloc(&client->dev,
>>>> +                           sizeof(struct lm3601x_led), GFP_KERNEL);
>>>
>>> sizeof(*led) and one line in the result
> 
> And this?

Ack.

> 
>>>> +       { },
>>>
>>> Terminators better w/o comma.
>>
>> Looking at other drivers adding comma's on the sentinel is accepted.  See the as3645a driver
> 
> So what?
> 
> Terminator at compile time even better.
> 
>>>> +       {},
>>>
>>> Ditto.
>>
>> See above
> 
> See above.
> 

-- 
Best regards,
Jacek Anaszewski