linux-kernel - Re: [PATCH v2 2/3] iommu/tegra-smmu: Rework .probe_device and .attach

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Date:   Wed, 30 Sep 2020 09:10:38 +0300
From:   Dmitry Osipenko <digetx@...il.com>
To:     Nicolin Chen <nicoleotsuka@...il.com>
Cc:     thierry.reding@...il.com, joro@...tes.org, krzk@...nel.org,
        vdumpa@...dia.com, jonathanh@...dia.com,
        linux-tegra@...r.kernel.org, iommu@...ts.linux-foundation.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 2/3] iommu/tegra-smmu: Rework .probe_device and
 .attach_dev

30.09.2020 08:49, Nicolin Chen пишет:
> On Wed, Sep 30, 2020 at 08:11:52AM +0300, Dmitry Osipenko wrote:
>> 30.09.2020 03:30, Nicolin Chen пишет:
>>> +	/* An invalid mc pointer means mc and smmu drivers are not ready */
>>> +	if (IS_ERR_OR_NULL(mc))
>>
>> tegra_get_memory_controller() doesn't return NULL.
> 
> Well, I don't want to assume that it'd do that forever, and the
> NULL check of IS_ERR_OR_NULL is marked "unlikely" so it doesn't
> hurt to have.
> 

I don't see any reasons why it won't do that forever.

Secondly, public function can't be changed randomly without updating all
the callers.

Hence there is no need to handle cases that can't ever happen and it
hurts readability of the code + original error code is missed.