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SubjectRe: [PATCH 2/2] spi: devicetree: add support for loopback mode
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On Wed, 12 Dec 2012 10:46:00 +0200, Felipe Balbi <balbi@ti.com> wrote:
> there are a few spi master drivers which make
> use of that flag but there is no way to pass it
> through devicetree.
>
> This patch just creates a way to pass SPI_LOOP
> via devicetree.

I don't understand how this would be useful since loopback mode is
really just a test feature. Is there any reason to do loopback for
something other than test?

I think it would be better to add a sysfs or debugfs property to
manipulate the SPI_LOOP flag from userspace. What do you think?

g.

>
> Signed-off-by: Felipe Balbi <balbi@ti.com>
> ---
> Documentation/devicetree/bindings/spi/spi-bus.txt | 2 ++
> drivers/spi/spi.c | 2 ++
> 2 files changed, 4 insertions(+)
>
> diff --git a/Documentation/devicetree/bindings/spi/spi-bus.txt b/Documentation/devicetree/bindings/spi/spi-bus.txt
> index 296015e..1949586 100644
> --- a/Documentation/devicetree/bindings/spi/spi-bus.txt
> +++ b/Documentation/devicetree/bindings/spi/spi-bus.txt
> @@ -55,6 +55,8 @@ contain the following properties.
> chip select active high
> - spi-3wire - (optional) Empty property indicating device requires
> 3-wire mode.
> +- spi-loopback - (optional) Empty property indicating device requires
> + loopback mode.
>
> If a gpio chipselect is used for the SPI slave the gpio number will be passed
> via the cs_gpio
> diff --git a/drivers/spi/spi.c b/drivers/spi/spi.c
> index 3f1b9ee..6bcdc03 100644
> --- a/drivers/spi/spi.c
> +++ b/drivers/spi/spi.c
> @@ -868,6 +868,8 @@ static void of_register_spi_devices(struct spi_master *master)
> spi->mode |= SPI_CS_HIGH;
> if (of_find_property(nc, "spi-3wire", NULL))
> spi->mode |= SPI_3WIRE;
> + if (of_find_property(nc, "spi-loopback", NULL))
> + spi->mode |= SPI_LOOP;
>
> /* Device speed */
> prop = of_get_property(nc, "spi-max-frequency", &len);
> --
> 1.8.1.rc1.5.g7e0651a
>

--
Grant Likely, B.Sc, P.Eng.
Secret Lab Technologies, Ltd.


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