Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18;
Subject: Re: [PATCH v3 1/3] memory: tegra: Add
 devm_tegra_get_memory_controller()
To:     Thierry Reding <thierry.reding@gmail.com>
Cc:     Nicolin Chen <nicoleotsuka@gmail.com>, joro@8bytes.org,
        krzk@kernel.org, vdumpa@nvidia.com, jonathanh@nvidia.com,
        linux-tegra@vger.kernel.org, iommu@lists.linux-foundation.org,
        linux-kernel@vger.kernel.org
References: <20200930084258.25493-1-nicoleotsuka@gmail.com>
 <20200930084258.25493-2-nicoleotsuka@gmail.com>
 <20200930152320.GA3833404@ulmo>
 <ed7b4375-d06e-2750-e6fa-603ef2b60d36@gmail.com>
 <20200930160355.GC3833404@ulmo>
From:   Dmitry Osipenko <digetx@gmail.com>
Message-ID: <839df5d6-513f-3d77-ba5f-a1afe5d0883a@gmail.com>
Date:   Wed, 30 Sep 2020 19:06:27 +0300
User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101
 Thunderbird/68.10.0
MIME-Version: 1.0
In-Reply-To: <20200930160355.GC3833404@ulmo>
Content-Type: text/plain; charset=utf-8
Content-Language: en-US
Content-Transfer-Encoding: 8bit
Precedence: bulk

30.09.2020 19:03, Thierry Reding пишет:
> On Wed, Sep 30, 2020 at 06:53:06PM +0300, Dmitry Osipenko wrote:
>> 30.09.2020 18:23, Thierry Reding пишет:
>>> On Wed, Sep 30, 2020 at 01:42:56AM -0700, Nicolin Chen wrote:
>>>> From: Dmitry Osipenko <digetx@gmail.com>
>>>>
>>>> Multiple Tegra drivers need to retrieve Memory Controller and hence there
>>>> is quite some duplication of the retrieval code among the drivers. Let's
>>>> add a new common helper for the retrieval of the MC.
>>>>
>>>> Signed-off-by: Dmitry Osipenko <digetx@gmail.com>
>>>> Signed-off-by: Nicolin Chen <nicoleotsuka@gmail.com>
>>>> ---
>>>>
>>>> Changelog
>>>> v2->v3:
>>>>  * Replaced with Dimtry's devm_tegra_get_memory_controller()
>>>> v1->v2:
>>>>  * N/A
>>>>
>>>>  drivers/memory/tegra/mc.c | 39 +++++++++++++++++++++++++++++++++++++++
>>>>  include/soc/tegra/mc.h    | 17 +++++++++++++++++
>>>>  2 files changed, 56 insertions(+)
>>>
>>> Let's not add this helper, please. If a device needs a reference to the
>>> memory controller, it should have a phandle to the memory controller in
>>> device tree so that it can be looked up explicitly.
>>>
>>> Adding this helper is officially sanctioning that it's okay not to have
>>> that reference and that's a bad idea.
>>
>> And please explain why it's a bad idea, I don't see anything bad here at
>> all.
> 
> Well, you said yourself in a recent comment that we should avoid global
> variables. devm_tegra_get_memory_controller() is nothing but a glorified
> global variable.

This is not a variable, but a common helper function which will remove
the duplicated code and will help to avoid common mistakes like a missed
put_device().