Re: [ath9k-devel] [PATCH v2] ath9k: collect statistics about Rx-Dup and Rx-STBC packets

[Felix Fietkau <nbd@openwrt.org>]

On 2013-04-27 9:06 PM, Adrian Chadd wrote:
> On 27 April 2013 11:53, Oleksij Rempel <linux@rempel-privat.de> wrote:
> 
>>> (And then go and re-align things inside that struct so you don't waste
>>> space.)
>>
>>
>> hmm.. what do you mean here?
> 
> Structure alignment? Well, you typically want to have everything be
> dword aligned (32 bits) or word (16 bits) aligned. Otherwise the
> compiler may insert extra padding between fields in order to meet
> alignment requirements on platforms that need it (MIPS, older ARM) or
> platforms that perform slower (newer ARM.)
I think in struct ath_rx_status alignment does not matter much, it's
only kept on the stack anyway. But yes, in other cases it makes sense to
pay attention to padding to keep structs small. I also agree that making
rs_flags u16 is a good idea.

> Now, i don't know what 'bool' is, whether it's a byte, word or dword.
bool is a byte.

> That "is_mybeacon" field should probably be just another flag in
> rx_status, then just extend 'rs_flags' to 16 bits and include it. That
> way the alignment is easy to see - all the fields in rx_status and the
> htc rx_status structs have explicit sizes. :-)
> 
> Felix, what do you think?
Sounds good :)

- Felix