linux-kernel - Re: [PATCH 2/5] nvmem: mtk-efuse: use stack for nvmem

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Date:   Fri, 22 Sep 2017 11:59:47 +0800
From:   Sean Wang <sean.wang@...iatek.com>
To:     Masahiro Yamada <yamada.masahiro@...ionext.com>
CC:     Srinivas Kandagatla <srinivas.kandagatla@...aro.org>,
        Jassi Brar <jaswinder.singh@...aro.org>,
        Keiji Hayashibara <hayashibara.keiji@...ionext.com>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        "moderated list:ARM/Mediatek SoC support" 
        <linux-mediatek@...ts.infradead.org>,
        Masami Hiramatsu <mhiramat@...nel.org>,
        Matthias Brugger <matthias.bgg@...il.com>,
        linux-arm-kernel <linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCH 2/5] nvmem: mtk-efuse: use stack for nvmem_config
 instead of malloc'ing it

Hi, Masahiro

On Thu, 2017-09-21 at 11:09 +0900, Masahiro Yamada wrote:
> Hi Sean,
> 
> 
> 2017-09-21 1:32 GMT+09:00 Sean Wang <sean.wang@...iatek.com>:
> > Hi, Masahiro
> >
> > For maintainability, I felt it's better if we use the same way to
> > register nvmem as that most drivers does under nvmem usually using
> > static structure. Otherwise, they should also be changed to use the
> > one-time data in stack to avoid extra bytes to keep them.
> >
> >         Sean
> 
> 
> Srinivas and I discussed the best practice for allocating nvmem_config.
> https://lkml.org/lkml/2017/9/11/4
> 
> From the discussion, static structure is possible only when
> the system has one instance of the device.
> 

thank you for your detailed explanation

> If you know this is the case for mediatek,
> yes, you can turn it into static,
> but it is not always possible.
> For example, Socionext SoCs have
> two banks of efuse devices.
> 

there should be only one instance of nvmem for mediatek soc, currently


> So, if we want to align the coding style for consistency,
> nvmem in stack is safe and efficient, I think.
> 
> 
> Moving one-time data into stack slightly
> reduces the kernel image size.
> 
> 

agreed on those statements, indeed bigger struct uart_8250_port is still
used on stack for configuring in a lot 8250 driver, so 

Acked-by: Sean Wang <sean.wang@...iatek.com>