Dan Williams wrote:
> On Fri, 2007-12-07 at 18:12 -0800, David Miller wrote:
>> From: Dan Williams <dcbw-H+wXaHxf7aLQT0dZR+AlfA@xxxxxxxxxxxxxxxx>
>> Date: Fri, 07 Dec 2007 19:22:46 -0500
>>
>>> @@ -1040,6 +1049,16 @@ struct iw_range
>>> * because each entry contain its channel index */
>>>
>>> __u32 enc_capa; /* IW_ENC_CAPA_* bit field */
>>> +
>>> + /* Do *NOT* use those fields, they are just used as padding to get
>>> + * proper alignement with user space */
>>> + __s32 reserved1;
>>> + __s32 reserved2;
>>> + __u16 reserved3;
>>> + __s32 reserved4;
>>> + __u32 reserved5;
>>> +
>>> + __u32 scan_capa; /* IW_SCAN_CAPA_* bit field */
>>> };
>>>
>>> /*
>> Major NACK. These datastructure usages are complete wrong, and
>> we have to stop spreading this problem instead of continuing on
>> with it as if it's OK.
>
> There's not too much we can do here. We need a better way to support
> driver/card capabilities in WEXT right _now_, in parallel with
> cfg80211/nl80211. The other alternative here is to have a 64-bit
> generic capabilities field-to-end-all-fields and add more bitfield
> position constants to that without extending the structure any more.
>
> Is there a better way you'd propose to do this _in_WEXT_?
Since iw_range is not packed, there are a few locations where there is some padding. You could quite easily shoehorn an 8 bit bitmask into the existing structure without impacting backward compatibility (unless userspace is using the padding for something). For example:
--- a/include/linux/wireless.h
+++ b/include/linux/wireless.h
@@ -1035,6 +1035,7 @@ struct iw_range
/* Frequency */
__u16 num_channels; /* Number of channels [0; num - 1] */
__u8 num_frequency; /* Number of entry in the list */
+ __u8 scan_capa; /* scan capabilities */
struct iw_freq freq[IW_MAX_FREQUENCIES]; /* list */
/* Note : this frequency list doesn't need to fit channel numbers,
* because each entry contain its channel index */
Other candidate blocks are Old Frequency, Rates, Encoder stuff, Transmit power.
Dave.
> I don't really forsee any more extending of this structure, since I
> think scan capabilities are the last thing we really need to know about.
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