linux-kernel - Re: [PATCH v3 1/3] memory: tegra: Add devm_tegra_get_memory

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Date:   Wed, 30 Sep 2020 19:06:27 +0300
From:   Dmitry Osipenko <digetx@...il.com>
To:     Thierry Reding <thierry.reding@...il.com>
Cc:     Nicolin Chen <nicoleotsuka@...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 v3 1/3] memory: tegra: Add
 devm_tegra_get_memory_controller()

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@...il.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@...il.com>
>>>> Signed-off-by: Nicolin Chen <nicoleotsuka@...il.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().