linux-kernel - Re: [RFC RFT PATCH 0/4] gpiolib: speed up GPIO array processing

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Message-ID: <1595423.PPW7Q1vFt0@z50>
Date:   Wed, 29 Aug 2018 20:16:20 +0200
From:   Janusz Krzysztofik <jmkrzyszt@...il.com>
To:     Linus Walleij <linus.walleij@...aro.org>
Cc:     Jonathan Corbet <corbet@....net>,
        Miguel Ojeda Sandonis <miguel.ojeda.sandonis@...il.com>,
        Peter Korsgaard <peter.korsgaard@...co.com>,
        Peter Rosin <peda@...ntia.se>,
        Ulf Hansson <ulf.hansson@...aro.org>,
        Andrew Lunn <andrew@...n.ch>,
        Florian Fainelli <f.fainelli@...il.com>,
        "David S. Miller" <davem@...emloft.net>,
        Dominik Brodowski <linux@...inikbrodowski.net>, kishon@...com,
        Lars-Peter Clausen <lars@...afoo.de>,
        Michael Hennerich <Michael.Hennerich@...log.com>,
        Jonathan Cameron <jic23@...nel.org>,
        Hartmut Knaack <knaack.h@....de>,
        Peter Meerwald <pmeerw@...erw.net>,
        Greg KH <gregkh@...uxfoundation.org>,
        Jiri Slaby <jslaby@...e.com>,
        "open list:GPIO SUBSYSTEM" <linux-gpio@...r.kernel.org>,
        linux-doc@...r.kernel.org, linux-i2c@...r.kernel.org,
        linux-mmc <linux-mmc@...r.kernel.org>,
        netdev <netdev@...r.kernel.org>, linux-iio@...r.kernel.org,
        devel@...verdev.osuosl.org, linux-serial@...r.kernel.org,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Janusz Krzysztofik <jmkrzyszt@...il.com>
Subject: Re: [RFC RFT PATCH 0/4] gpiolib: speed up GPIO array processing

Hi Linus,

On Wednesday, August 29, 2018 11:06:21 AM CEST Linus Walleij wrote:
> On Tue, Aug 21, 2018 at 1:42 AM Janusz Krzysztofik <jmkrzyszt@...il.com> 
wrote:
> 
> > This series is a follow up of the former "mtd: rawnand: ams-delta: Use
> > gpio-omap accessors for data I/O" which already contained some changes
> > to gpiolib.  Those previous attempts were commented by Borris Brezillon
> > who suggested using GPIO API modified to accept bitmaps, and by Linus
> > Walleij who suggested still more great ideas for further immprovement
> > of the proposed API changes - thanks!
> >
> > The goal is to boost performans of get/set array functions while
> > processing GPIO arrays which represent pins of a signle chip in
> > hardware order.  If resulting performance is close to PIO, GPIO API
> > can be used for data I/O without much loss of speed.
> 
> Hands down, this is a very pretty patch set. I'm a big fan already.
> 
> This is mainly because it fulfills the requirement for libraries
> to be narrow and deep, which is what we want.
> This refers to John Ousterhouts software design philosophy,
> here is a great lecture if you haven't seen it already:
> https://www.youtube.com/watch?v=bmSAYlu0NcY
> 
> Let's get this into v1 and get some testing and merge it for v4.20
> ASAP

Please hold on for a while, I'm going to resubmit soon, with the comment from 
Peter Rosin on i2c-mux-gpio addressed and the error discovered by Miguel Ojeda 
in hd44780 fixed.

Thanks,
Janusz

> so we get some proper testing before the v4.20 merge
> window. It would be excellent if some of the current users of
> the array API could provide tested-by's or at least ACKs.
> 
> For example ts-nbus.c must be a big benefactor.
> 
> Yours,
> Linus Walleij
>