linux-kernel - Re: [PATCH v1 1/5] gpio: max77620: Initialize interrupts state

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Date:   Wed, 8 Jul 2020 12:41:46 +0300
From:   Dmitry Osipenko <digetx@...il.com>
To:     Andy Shevchenko <andy.shevchenko@...il.com>
Cc:     Thierry Reding <thierry.reding@...il.com>,
        Jonathan Hunter <jonathanh@...dia.com>,
        Laxman Dewangan <ldewangan@...dia.com>,
        Bartosz Golaszewski <bgolaszewski@...libre.com>,
        Linus Walleij <linus.walleij@...aro.org>,
        linux-tegra@...r.kernel.org,
        "open list:GPIO SUBSYSTEM" <linux-gpio@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v1 1/5] gpio: max77620: Initialize interrupts state

08.07.2020 11:51, Andy Shevchenko пишет:
> On Wed, Jul 8, 2020 at 11:29 AM Dmitry Osipenko <digetx@...il.com> wrote:
>>
>> I noticed on Nexus 7 that after rebooting from downstream kernel to
>> upstream, the GPIO interrupt is triggering non-stop despite of interrupts
>> being disabled for all of GPIOs. This happens because Nexus 7 uses a
>> soft-reboot, meaning that bootloader should take care of resetting
>> hardware, but bootloader doesn't do it well. In a result, GPIO interrupt
>> may be left ON at a boot time. Let's mask all GPIO interrupts at the
>> driver's probe time in order to resolve the issue.
> 
> ...
> 
>> +               err = regmap_update_bits(mgpio->rmap, GPIO_REG_ADDR(i),
>> +                                        MAX77620_CNFG_GPIO_INT_MASK, 0);
>> +               if (err < 0)
> 
> Does ' < 0' meaningful here?

Not really, although [1] explicitly says that regmap_update_bits()
returns either 0 or a negative error code. The positive value will be an
unexpected return code here.

[1]
https://elixir.bootlin.com/linux/v5.8-rc3/source/drivers/base/regmap/regmap.c#L2910

This variant of ' < 0' is consistent with all other similar occurrences
in the driver's code, so should be better to keep it as-is, IMO.

>> +                       dev_err(mgpio->dev, "failed to disable interrupt: %d\n",
>> +                               err);
> 
> One line.

This will make this line inconsistent with the rest of the driver's code.

Secondly, this line won't fit to display using my multi-file view-edit
setup.

I know that 80 chars isn't warned by checkpatch anymore, but still it's
a preferred width for all cases where it doesn't hurt readability, which
is the case here, IMO.