linux-kernel - Re: [PATCH] spi: spi-gpio: Don't set MOSI as an input if not 3WIRE mode

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Message-ID: <Y5EzD8AaAj0EGnvH@sirena.org.uk>
Date:   Thu, 8 Dec 2022 00:42:55 +0000
From:   Mark Brown <broonie@...nel.org>
To:     Kris Bahnsen <kris@...eddedts.com>
Cc:     linux-spi@...r.kernel.org, linux-kernel@...r.kernel.org,
        mark@...eddedts.com
Subject: Re: [PATCH] spi: spi-gpio: Don't set MOSI as an input if not 3WIRE
 mode

On Wed, Dec 07, 2022 at 04:36:41PM -0800, Kris Bahnsen wrote:
> On Wed, 2022-12-07 at 23:44 +0000, Mark Brown wrote:

> > A cleaner fix which is probably marginally more performant would be to
> > make the setting of spi_gpio_set_direction() conditional on SPI_3WIRE -
> > then we won't call into the function at all when not doing 3 wire,
> > avoiding the issue entirely.

> That makes sense to me. I was operating under the assumption that 3WIRE
> mode could be switched in to at a later time via ioctl(), but with the
> death of spidev that is presumably no longer a concern.

Ugh, right, spidev.  Really even with spidev devices should probably
have the mode configured beforehand (I'm not sure pinmux will do the
right thing on most platforms...) but now I check it's part of the ABI
so we can't get rid of it and therefore your current patch probably is
what we need.  No need to reroll, sorry for the noise :/

I'm not sure why you think spidev is dying, it does still exist and
devices use it?

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