linux-kernel - Re: [V2, 2/6] tty: serial: lpuart: add little endian 32 bit register support

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Message-ID: <20170517070019.GG9913@b29396-OptiPlex-7040>
Date:   Wed, 17 May 2017 15:00:19 +0800
From:   Dong Aisheng <dongas86@...il.com>
To:     Nikita Yushchenko <nikita.yoush@...entembedded.com>
Cc:     "A.S. Dong" <aisheng.dong@....com>,
        "linux-serial@...r.kernel.org" <linux-serial@...r.kernel.org>,
        Andy Duan <fugang.duan@....com>,
        "gregkh@...uxfoundation.org" <gregkh@...uxfoundation.org>,
        "Y.B. Lu" <yangbo.lu@....com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "stefan@...er.ch" <stefan@...er.ch>,
        Mingkai Hu <mingkai.hu@....com>,
        "jslaby@...e.com" <jslaby@...e.com>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>
Subject: Re: [V2, 2/6] tty: serial: lpuart: add little endian 32 bit register
 support

On Wed, May 17, 2017 at 09:25:51AM +0300, Nikita Yushchenko wrote:
> >> Code should be consistent.
> >>
> > 
> > Yes.
> > 
> >> There is no good reason to have sport->lpuart32 inside sport, but
> >> lpuart_is_be outside of it. Both these values describe properties of
> >> particular device, and thus should be in per-device structure.
> >>
> > 
> > That's for special case, normally we wouldn't do that.
> 
> For me this "special case" looks like "let's break data structure
> consistency to reuse several lines of code".
> 
> With code snippets you show, it looks even worse: you assign same global
> variable in several places for different uses. 

If you mean lpuart_is_be, it's not for different uses.
The purpose is the same to align the correct endian but in two places.

> implicitly assuming that
> it is for same device. Which can be true in your current system, but not
> elsewhere (e.g. why not having lpuart programmed into fpga)?
> 

Sorry, What issues for fpga?

> Alternative solution could be - have separate write path for earlycon.

It looks to me having the same issue with a separate write patch
for earlycon as we still need distinguish Little or Big endian
for Layerscape and IMX.

> At a glance, it is dozen lines of code.

Would you please show some sample code?
Then we probably may understand better with each other.

Anyway, thanks for detailed review.

Regards
Dong Aisheng