linux-kernel - Re: [PATCH 2/2] gpiolib: Fix array members of same chip processed separately

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Message-ID: <CACRpkdbF=Yda3Wqii6dkDjqPzuh43Vb4nvPVrxLet3MYo0qUrw@mail.gmail.com>
Date:   Mon, 24 Sep 2018 10:13:02 +0200
From:   Linus Walleij <linus.walleij@...aro.org>
To:     Janusz Krzysztofik <jmkrzyszt@...il.com>
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>,
        Greg KH <gregkh@...uxfoundation.org>, 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>,
        Jiri Slaby <jslaby@...e.com>, Willy Tarreau <w@....eu>,
        Geert Uytterhoeven <geert@...ux-m68k.org>,
        Sebastien Bourdelin <sebastien.bourdelin@...oirfairelinux.com>,
        Lukas Wunner <lukas@...ner.de>,
        Rojhalat Ibrahim <imr@...chenk.de>,
        Russell King <rmk+kernel@...linux.org.uk>,
        ext Tony Lindgren <tony@...mide.com>,
        Yegor Yefremov <yegorslists@...glemail.com>,
        Uwe Kleine-König 
        <u.kleine-koenig@...gutronix.de>, 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,
        "open list:GPIO SUBSYSTEM" <linux-gpio@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Marek Szyprowski <m.szyprowski@...sung.com>,
        Krzysztof Kozlowski <krzk@...nel.org>,
        linux-samsung-soc <linux-samsung-soc@...r.kernel.org>
Subject: Re: [PATCH 2/2] gpiolib: Fix array members of same chip processed separately

On Mon, Sep 24, 2018 at 1:52 AM Janusz Krzysztofik <jmkrzyszt@...il.com> wrote:

> New code introduced by commit bf9346f5d47b ("gpiolib: Identify arrays
> matching GPIO hardware") forcibly tries to find an array member which
> has its array index number equal to its hardware pin number and set
> up an array info for possible fast bitmap processing of all arrray
> pins belonging to that chip which also satisfy that numbering rule.
>
> Depending on array content, it may happen that consecutive array
> members which belong to the same chip but don't have array indexes
> equal to their pin hardware numbers will be split into groups, some of
> them processed together via the fast bitmap path, and rest of them
> separetely.  However, applications may expect all those pins being
> processed together with a single call to .set_multiple() chip callback,
> like that was done before the change.
>
> Limit applicability of fast bitmap processing path to cases where all
> pins of consecutive array members starting from 0 which belong to the
> same chip have their hardware numbers equal to their corresponding
> array indexes.  That should still speed up processing of applications
> using whole GPIO banks as I/O ports, while not breaking simultaneous
> manipulation of consecutive pins of the same chip which don't follow
> the equal numbering rule.
>
> Cc: Jonathan Corbet <corbet@....net>
> Signed-off-by: Janusz Krzysztofik <jmkrzyszt@...il.com>

Patch applied!

Yours,
Linus Walleij