netdev - Re: [PATCH v7 1/4] gpiolib: Pass bitmaps, not integer arrays, to get/set array

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Message-ID: <20180903043129.GA17856@bombadil.infradead.org>
Date:   Sun, 2 Sep 2018 21:31:29 -0700
From:   Matthew Wilcox <willy@...radead.org>
To:     Janusz Krzysztofik <jmkrzyszt@...il.com>
Cc:     Linus Walleij <linus.walleij@...aro.org>,
        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 Kroah-Hartman <gregkh@...uxfoundation.org>,
        Kishon Vijay Abraham I <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-Stadler <pmeerw@...erw.net>,
        Jiri Slaby <jslaby@...e.com>, Willy Tarreau <w@....eu>,
        Geert Uytterhoeven <geert@...ux-m68k.org>,
        linux-doc@...r.kernel.org, linux-i2c@...r.kernel.org,
        linux-mmc@...r.kernel.org, netdev@...r.kernel.org,
        linux-iio@...r.kernel.org, devel@...verdev.osuosl.org,
        linux-serial@...r.kernel.org, linux-gpio@...r.kernel.org,
        linux-kernel@...r.kernel.org,
        Sebastien Bourdelin <sebastien.bourdelin@...oirfairelinux.com>,
        Lukas Wunner <lukas@...ner.de>,
        Rojhalat Ibrahim <imr@...chenk.de>,
        Russell King <rmk+kernel@...linux.org.uk>,
        Tony Lindgren <tony@...mide.com>,
        Yegor Yefremov <yegorslists@...glemail.com>,
        Uwe Kleine-König 
        <u.kleine-koenig@...gutronix.de>, linuxppc-dev@...ts.ozlabs.org
Subject: Re: [PATCH v7 1/4] gpiolib: Pass bitmaps, not integer arrays, to
 get/set array

> +++ b/drivers/auxdisplay/hd44780.c
> @@ -62,17 +62,12 @@ static void hd44780_strobe_gpio(struct hd44780 *hd)
>  /* write to an LCD panel register in 8 bit GPIO mode */
>  static void hd44780_write_gpio8(struct hd44780 *hd, u8 val, unsigned int rs)
>  {
> -	int values[10];	/* for DATA[0-7], RS, RW */
> -	unsigned int i, n;
> -
> -	for (i = 0; i < 8; i++)
> -		values[PIN_DATA0 + i] = !!(val & BIT(i));
> -	values[PIN_CTRL_RS] = rs;
> -	n = 9;
> -	if (hd->pins[PIN_CTRL_RW]) {
> -		values[PIN_CTRL_RW] = 0;
> -		n++;
> -	}
> +	DECLARE_BITMAP(values, 10); /* for DATA[0-7], RS, RW */
> +	unsigned int n;
> +
> +	*values = val;
> +	__assign_bit(8, values, rs);
> +	n = hd->pins[PIN_CTRL_RW] ? 10 : 9;

Doesn't this assume little endian bitmaps?  Has anyone tested this on
big-endian machines?