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[Xen-devel] RE: [PATCH]enable PCI serial card usage

To: Keir Fraser <keir.fraser@xxxxxxxxxxxxx>, "xen-devel@xxxxxxxxxxxxxxxxxxx" <xen-devel@xxxxxxxxxxxxxxxxxxx>
Subject: [Xen-devel] RE: [PATCH]enable PCI serial card usage
From: "Wei, Gang" <gang.wei@xxxxxxxxx>
Date: Wed, 31 Mar 2010 17:19:57 +0800
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Thread-topic: [PATCH]enable PCI serial card usage
On Wednesday, 2010-3-31 5:09 PM, Keir Fraser wrote:
> On 31/03/2010 03:40, "Wei, Gang" <gang.wei@xxxxxxxxx> wrote:
>> +    int pb_bdf_enable:1;    /* if =1, pb-bdf effective, port behind
>> bridge */ +    int ps_bdf_enable:1;    /* if =1, ps_bdf effective,
>> port on pci card */ 
> Point of information for you: a signed integer N-bit bit field can
> take values in the range -2^(N-1) to 2^(N-1)-1. In this case N=1 and
> the allowed values are -1 and 0. Hence assigning value 1 to the above
> bit fields has undefined behaviour and some versions of gcc will not
> 'set the flag' as you expect! We've been bitten by it before.
> Generally your bit fields should be *unsigned* unless you
> specifically want signed-integer semantics. Even better here, we'll
> burn the extra bits and use xen_bool_t. 
> I will fix your patch in this case before applying.

Thanks for point it out. xen_bool_t would be safer for such case.

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