Re: [patch 2.6.22-rc2-git] spidev compiler warning gone

[Andrew Morton <akpm-de/tnXTf+JLsfHDXvbKv3WD2FQJk+8+b@public.gmane.org>]

On Fri, 25 May 2007 10:35:07 -0700
David Brownell <david-b-yBeKhBN/0LDR7s880joybQ@public.gmane.org> wrote:

> Get rid of annoying GCC warning on 32-bit platforms.  The trick is to
> add an extra cast using "ptrdiff_t" to convert the u64 to the correct
> size integer, and only then casting it into a "void *" pointer.
> 
> Signed-off-by: David Brownell <dbrownell-Rn4VEauK+AKRv+LV9MX5uipxlwaOVQ5f@public.gmane.org>
> ---
>  drivers/spi/spidev.c |    6 ++++--
>  1 file changed, 4 insertions(+), 2 deletions(-)
> 
> --- g26.orig/drivers/spi/spidev.c	2007-05-24 12:04:46.000000000 -0700
> +++ g26/drivers/spi/spidev.c	2007-05-25 10:31:56.000000000 -0700
> @@ -181,7 +181,8 @@ static int spidev_message(struct spidev_
>  		}
>  		if (u_tmp->tx_buf) {
>  			k_tmp->tx_buf = buf;
> -			if (copy_from_user(buf, (const u8 __user *)u_tmp->tx_buf,
> +			if (copy_from_user(buf, (const u8 __user *)
> +						(ptrdiff_t) u_tmp->tx_buf,
>  					u_tmp->len))
>  				goto done;
>  		}
> @@ -213,7 +214,8 @@ static int spidev_message(struct spidev_
>  	buf = spidev->buffer;
>  	for (n = n_xfers, u_tmp = u_xfers; n; n--, u_tmp++) {
>  		if (u_tmp->rx_buf) {
> -			if (__copy_to_user((u8 __user *)u_tmp->rx_buf, buf,
> +			if (__copy_to_user((u8 __user *)
> +					(ptrdiff_t) u_tmp->rx_buf, buf,
>  					u_tmp->len)) {
>  				status = -EFAULT;
>  				goto done;

This seems overly tricky.  The way we normally squish that warning is
via a (long) cast.

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