Re: [RFC 04/25] spi: gpio: Implement LSB First bitbang support

From: Mark Brown <broonie@kernel.org>
To: "Andreas Färber" <afaerber@suse.de>
Cc: Geert Uytterhoeven <geert@linux-m68k.org>,
	linux-realtek-soc@lists.infradead.org,
	linux-leds@vger.kernel.org,
	Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
	linux-spi <linux-spi@vger.kernel.org>,
	Jacek Anaszewski <jacek.anaszewski@gmail.com>,
	Pavel Machek <pavel@ucw.cz>,
	Linux ARM <linux-arm-kernel@lists.infradead.org>,
	Dan Murphy <dmurphy@ti.com>
Subject: Re: [RFC 04/25] spi: gpio: Implement LSB First bitbang support
Date: Thu, 12 Dec 2019 17:19:22 +0000	[thread overview]
Message-ID: <20191212171922.GM4310@sirena.org.uk> (raw)
In-Reply-To: <9b4b6287-c1d9-1b41-88a8-7ac9fe222642@suse.de>

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On Thu, Dec 12, 2019 at 04:14:59PM +0100, Andreas Färber wrote:
> Am 12.12.19 um 09:40 schrieb Geert Uytterhoeven:
> > On Thu, Dec 12, 2019 at 4:41 AM Andreas Färber <afaerber@suse.de> wrote:
> >> Add support for slave DT property spi-lsb-first, i.e., SPI_LSB_FIRST mode.

> >> Duplicate the inline helpers bitbang_txrx_be_cpha{0,1} as LE versions.
> >> Make checkpatch.pl happy by changing "unsigned" to "unsigned int".

Separate patch for this?

> So from that angle I don't see a better way than either duplicating the
> functions or using some macro magic to #include the header twice. If we
> wanted to go down that path, we could probably de-duplicate the existing
> two functions, too, but I was trying to err on the cautious side, since
> I don't have setups to test all four code paths myself (and a ton of
> more relevant but less fun patches to flush out ;)).

Yeah, I don't think there's any great options here with the potential
performance issues - probably the nicest thing would be to autogenerate
lots of variants but I think that's far more trouble than it's worth.

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