linux-kernel - Re: [PATCH] spi-gpio: Sanitize MISO bitvalue

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Message-Id: <200902161158.48890.david-b@pacbell.net>
Date:	Mon, 16 Feb 2009 11:58:48 -0800
From:	David Brownell <david-b@...bell.net>
To:	Michael Buesch <mb@...sch.de>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	linux-kernel@...r.kernel.org, openwrt-devel@...ts.openwrt.org
Subject: Re: [PATCH] spi-gpio: Sanitize MISO bitvalue

On Sunday 15 February 2009, Michael Buesch 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@...sch.de>

Acked-by: David Brownell <dbrownell@...rs.sourceforge.net>


> ---
> 
> Well, we could also change the bitbang helpers in linux/spi/spi_bitbang.h

That would be the main alternate fix to consider, and
it's worth updating the docs there to specify that getmiso()
needs to return 0/1 ... 

> or change the way the gpio_get_value API is defined,

Not an option.  The more instructions thrown in these
inner loops, the harder it is to get even inlined code to
clock over 1 MHz.


> 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
> 
> -- 
> Greetings, Michael.
> 
> 



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