linux-kernel - Re: [PATCH v5] gpio: sim: fix an invalid _

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Date:   Thu, 21 Sep 2023 01:12:16 -0700
From:   Bartosz Golaszewski <brgl@...ev.pl>
To:     Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
Cc:     Linus Walleij <linus.walleij@...aro.org>,
        Kent Gibson <warthog618@...il.com>,
        Alexey Dobriyan <adobriyan@...il.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        akpm@...ux-foundation.org, linux-gpio@...r.kernel.org,
        linux-kernel@...r.kernel.org,
        Bartosz Golaszewski <bartosz.golaszewski@...aro.org>,
        Bartosz Golaszewski <brgl@...ev.pl>
Subject: Re: [PATCH v5] gpio: sim: fix an invalid __free() usage

On Wed, 20 Sep 2023 15:43:47 +0200, Andy Shevchenko
<andriy.shevchenko@...ux.intel.com> said:
> On Wed, Sep 20, 2023 at 09:32:53AM +0200, Bartosz Golaszewski wrote:
>> From: Bartosz Golaszewski <bartosz.golaszewski@...aro.org>
>>
>> gpio_sim_make_line_names() returns NULL or ERR_PTR() so we must not use
>> __free(kfree) on the returned address. Split this function into two, one
>> that determines the size of the "gpio-line-names" array to allocate and
>> one that actually sets the names at correct offsets. The allocation and
>> assignment of the managed pointer happens in between.
>
> ...
>
>>  	list_for_each_entry(line, &bank->line_list, siblings) {
>> -		if (line->offset >= bank->num_lines)
>> +		if (!line->name || (line->offset >= bank->num_lines))
>>  			continue;
>>
>> -		if (line->name) {
>> -			if (line->offset > max_offset)
>> -				max_offset = line->offset;
>> -
>> -			/*
>> -			 * max_offset can stay at 0 so it's not an indicator
>> -			 * of whether line names were configured at all.
>> -			 */
>> -			has_line_names = true;
>> -		}
>> +		size = max(size, line->offset + 1);
>>  	}
>
> As for the material to be backported it's fine, but I'm wondering if we
> actually can add the entries in a sorted manner, so we would need the exact
> what I mentioned in previous review round, just search backwards to the first
> satisfying entry. I don't believe the adding an entry to the list is a
> hot-path, so would be fine to call list_sort().
>

Given the need for the callback function, this would result in bigger code.

Also calling:

    list_add_tail();
    list_sort();

is not very elegant. I would possibly go for adding list_add_sorted() but
that's a separate change for the future.

Bart