linux-kernel - Re: serial driver cleanups v2

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Date:   Fri, 15 Mar 2019 20:11:18 +0200
From:   Andy Shevchenko <andy.shevchenko@...il.com>
To:     "Enrico Weigelt, metux IT consult" <lkml@...ux.net>
Cc:     "Enrico Weigelt, metux IT consult" <info@...ux.net>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Eric Anholt <eric@...olt.net>,
        Stefan Wahren <stefan.wahren@...e.com>,
        Florian Fainelli <f.fainelli@...il.com>,
        Ray Jui <rjui@...adcom.com>,
        Scott Branden <sbranden@...adcom.com>,
        bcm-kernel-feedback-list <bcm-kernel-feedback-list@...adcom.com>,
        Vladimir Zapolskiy <vz@...ia.com>,
        Matthias Brugger <matthias.bgg@...il.com>,
        Masahiro Yamada <yamada.masahiro@...ionext.com>,
        Tobias Klauser <tklauser@...tanz.ch>,
        Richard Genoud <richard.genoud@...il.com>,
        macro@...ux-mips.org,
        Uwe Kleine-König 
        <u.kleine-koenig@...gutronix.de>,
        Sascha Hauer <kernel@...gutronix.de>, slemieux.tyco@...il.com,
        Andy Gross <andy.gross@...aro.org>,
        David Brown <david.brown@...aro.org>,
        Shawn Guo <shawnguo@...nel.org>,
        Sascha Hauer <s.hauer@...gutronix.de>,
        Fabio Estevam <festevam@...il.com>,
        dl-linux-imx <linux-imx@....com>, baohua@...nel.org,
        Peter Korsgaard <jacmet@...site.dk>,
        "open list:SERIAL DRIVERS" <linux-serial@...r.kernel.org>,
        linux-arm-msm@...r.kernel.org,
        "open list:LINUX FOR POWERPC PA SEMI PWRFICIENT" 
        <linuxppc-dev@...ts.ozlabs.org>
Subject: Re: serial driver cleanups v2

On Fri, Mar 15, 2019 at 11:36:04AM +0100, Enrico Weigelt, metux IT consult wrote:
> On 15.03.19 10:12, Andy Shevchenko wrote:
> 
> >> Part II will be about moving the mmio range from mapbase and
> >> mapsize (which are used quite inconsistently) to a struct resource
> >> and using helpers for that. But this one isn't finished yet.
> >> (if somebody likes to have a look at it, I can send it, too)
> > 
> > Let's do that way you are preparing a branch somewhere and anounce
> > here as an RFC, since this was neither tested nor correct.
> 
> Okay, here it is:
> 
> I. https://github.com/metux/linux/tree/submit/serial-clean-v3
>    --> general cleanups, as basis for II
> 
> II. https://github.com/metux/linux/tree/wip/serial-res
>    --> moving towards using struct resource consistently
> 
> III. https://github.com/metux/linux/tree/hack/serial
>     --> the final steps, which are yet completely broken
>     (more a notepad for things still to do :o)
> 
> The actual goal is generalizing the whole iomem handling, so individual
> usually just need to call some helpers that do most of the things.
> Finally, I also wanted to have all io region information consolidated
> in struct resource.

That's should be a selling point, not just conversion per se.

> > And selling point for many of them is not true: it doesn't make any
> > difference in the size in code, but increases a time to run
> > (devm_ioremap_resource() does more than plain devm_iomap() call).
> 
> Okay, just seen it. Does the the runtime overhead cause any problems ?

You have to explain that in each commit message, that the change does bring a
possible new error message printed.

The performance side of the deal, you are lucky here, is not significant
because it's slow path.

-- 
With Best Regards,
Andy Shevchenko