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SubjectRe: [PATCH] spi-gpio: Sanitize MISO bitvalue
On Sun, 15 Feb 2009 16:30:41 +0100
Michael Buesch <mb@bu3sch.de> wrote:

> gpio_get_value() returns 0 or nonzero, but getmiso() expects 0 or 1.
> Sanitize the value to a 0/1 boolean.
>
> Signed-off-by: Michael Buesch <mb@bu3sch.de>
>
> ---
>
> Well, we could also change the bitbang helpers in linux/spi/spi_bitbang.h
> or change the way the gpio_get_value API is defined, but I personally think
> this patch is pretty good as is.
> In any case, it fixes a real bug on platforms like the bcm47xx which
> return 0 or nonzero for gpio_get_value.
>
> Index: linux-2.6/drivers/spi/spi_gpio.c
> ===================================================================
> --- linux-2.6.orig/drivers/spi/spi_gpio.c 2009-02-14 21:37:14.000000000 +0100
> +++ linux-2.6/drivers/spi/spi_gpio.c 2009-02-15 16:27:16.000000000 +0100
> @@ -114,7 +114,7 @@ static inline void setmosi(const struct
>
> static inline int getmiso(const struct spi_device *spi)
> {
> - return gpio_get_value(SPI_MISO_GPIO);
> + return !!gpio_get_value(SPI_MISO_GPIO);
> }
>
> #undef pdata
>

Seems somewhat pointless, really. It's a very common C idiom to treat
any non-zero value as true, and the above just adds a couple more
instructions which we didn't need to execute.

If this function is speed-critical (which is what David's comment
implies) then perhaps this should be "fixed" by tightening up the
(presently apparently undocumented) interface? And then speeding up
all the other getmiso() implementations?


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