linux-kernel - Re: [PATCH v4 07/23] ata: libahci_platform: Convert to using devm bulk clocks API

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Date:   Thu, 16 Jun 2022 09:23:28 +0900
From:   Damien Le Moal <damien.lemoal@...nsource.wdc.com>
To:     Serge Semin <fancer.lancer@...il.com>
Cc:     Serge Semin <Sergey.Semin@...kalelectronics.ru>,
        Hans de Goede <hdegoede@...hat.com>,
        Jens Axboe <axboe@...nel.dk>, Hannes Reinecke <hare@...e.de>,
        Alexey Malahov <Alexey.Malahov@...kalelectronics.ru>,
        Pavel Parkhomenko <Pavel.Parkhomenko@...kalelectronics.ru>,
        Rob Herring <robh+dt@...nel.org>, linux-ide@...r.kernel.org,
        linux-kernel@...r.kernel.org, devicetree@...r.kernel.org
Subject: Re: [PATCH v4 07/23] ata: libahci_platform: Convert to using devm
 bulk clocks API

On 2022/06/16 5:45, Serge Semin wrote:
[...]
>>> +		hpriv->clks = devm_kzalloc(dev, sizeof(*hpriv->clks), GFP_KERNEL);
>>> +		if (!hpriv->clks) {
>>> +			rc = -ENOMEM;
>>> +			goto err_out;
>>> +		}
>>> +		hpriv->clks->clk = devm_clk_get_optional(dev, NULL);
> 
>>> +		if (IS_ERR(hpriv->clks->clk)) {
>>> +			rc = PTR_ERR(hpriv->clks->clk);
>>> +			goto err_out;
>>> +		} else if (hpriv->clks->clk) {
>>
>> Nit: the else is not needed here.
> 
> Well, it depends on what you see behind it. I see many reasons to keep
> it and only one tiny reason to drop it. Keeping it will improve the
> code readability and maintainability like having a more natural
> execution flow representation, thus clearer read-flow (else part as
> exception to the if part), less modifications should the goto part is
> changed/removed, a more exact program flow representation can be used
> by the compiler for some internal optimizations, it's one line shorter
> than the case we no 'else' here. On the other hand indeed we can drop
> it since if the conditional statement is true, the code afterwards
> won't be executed due to the goto operator. But as I see it dropping
> the else operator won't improve anything, but vise-versa will worsen
> the code instead. So if I get to miss something please justify why you
> want it being dropped, otherwise I would rather preserve it.

An else after a goto or return is never necessary and in my opinion makes the
code harder to read. I am not interested in debating this in general anyway. For
this particular case, the code would be:

		hpriv->clks->clk = devm_clk_get_optional(dev, NULL);
		if (IS_ERR(hpriv->clks->clk)) {
			/* Error path */
			rc = PTR_ERR(hpriv->clks->clk);
			goto err_out;
		}

		/* Normal path */
		if (hpriv->clks->clk) {
			...
		}

Which in my opinion is a lot easier to understand compared to having to parse
the if/else if and figure out which case in that sequence is normal vs error.

As noted, this is a nit. If you really insist, keep that else if.

> 
> -Sergey
> 
>>
>>> +			hpriv->clks->id = __clk_get_name(hpriv->clks->clk);
>>> +			hpriv->n_clks = 1;
>>>  		}
>>> -		hpriv->clks[i] = clk;
>>>  	}
>>>  
>>>  	hpriv->ahci_regulator = devm_regulator_get(dev, "ahci");
>>
>>
>> -- 
>> Damien Le Moal
>> Western Digital Research


-- 
Damien Le Moal
Western Digital Research