linux-kernel - Re: [PATCH v2 1/4] spi: spidev: Restore all SPI mode flags on ioctl failure

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Date:	Thu, 27 Feb 2014 09:59:42 +0100
From:	Geert Uytterhoeven <geert@...ux-m68k.org>
To:	Mark Brown <broonie@...nel.org>
Cc:	linux-spi <linux-spi@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Geert Uytterhoeven <geert+renesas@...ux-m68k.org>
Subject: Re: [PATCH v2 1/4] spi: spidev: Restore all SPI mode flags on ioctl failure

Hi Mark,

On Thu, Feb 27, 2014 at 5:50 AM, Mark Brown <broonie@...nel.org> wrote:
> > In commit f477b7fb13df2b843997559ff34e87d054ba6538 ("spi: DUAL and QUAD
> > support"), spi_device.mode was enlarged from 8 to 16 bits.
>
> Applied, thanks.

Thanks a lot!

>> For SPI_IOC_WR_MODE this is probably not so important, as it doesn't allow
>> setting Quad or Dual mode anyway, but SPI_IOC_WR_LSB_FIRST is used to just
>> set or clear a single bit.
>
> Since there's no API for it at present I'd not expect somethng that is
> using spidev to be able to have enabled any of the high mode bits.
> Unless I'm missing some path for this?

No, you're right.

While Quad mode could have been enabled in board info or DT, you can't use
it without setting [rt]x_nbits, and you can't share an SPI slave between spidev
and another driver[*]. I forgot about the latter.

[*] It would be a nice feature for debugging, though. In fact I'm
doing it, as the
    RSPI driver currently ignores the chip select number, so I have 3 m25p80
    drivers (in single, dual, resp. quad mode), and an spidev driver,
all talking to
    the same SPI FLASH.

Gr{oetje,eeting}s,

                        Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@...ux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds
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