linux-kernel - Re: I need help with a sparse warning

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Date:	Thu, 11 Sep 2008 19:32:37 -0700
From:	"Steven Noonan" <steven@...inklabs.net>
To:	"Larry Finger" <Larry.Finger@...inger.net>
Cc:	LKML <linux-kernel@...r.kernel.org>,
	wireless <linux-wireless@...r.kernel.org>
Subject: Re: I need help with a sparse warning

On Thu, Sep 11, 2008 at 7:13 PM, Larry Finger <Larry.Finger@...inger.net> wrote:
> In file drivers/net/wireless/p54/p54common.c, the statement
>
>       priv->rx_mtu = (size_t) le16_to_cpu((__le16)bootrec->data[10]);
>
> generates the sparse warning
>
> .../p54common.c:185:29: warning: cast to restricted __le16
>
> where bootrec->data is u32, and priv->rx_mtu is u16.
>

(Whoops, didn't CC the mailing lists. Sorry about the double-message, Larry.)

If priv->rx_mtu is u16, I'm surprised it doesn't get noisy about the
size_t cast. Unless the machine it's being compiled on is 16-bit, that
should throw a truncation warning, because size_t should be a 32-bit
integer on 32-bit machines (typically).

I think if you change the (__le16) cast to (__le16 __force) it will
stop warning you about that particular issue.

- Steven
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