netdev - Re: [PATCH net-next v4 1/4] ieee802154: add generic header handling routines

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Date:	Wed, 5 Mar 2014 20:15:56 +0100
From:	"Phoebe Buckheister" <phoebe.buckheister@...m.fraunhofer.de>
To:	"David Miller" <davem@...emloft.net>
Cc:	phoebe.buckheister@...m.fraunhofer.de, netdev@...r.kernel.org,
	linux-zigbee-devel@...ts.sourceforge.net
Subject: Re: [PATCH net-next v4 1/4] ieee802154: add generic header 
 handling routines

> From: Phoebe Buckheister <phoebe.buckheister@...m.fraunhofer.de>
> Date: Tue,  4 Mar 2014 15:34:45 +0100
>
>> +struct ieee802154_sechdr {
>> +	u8 sc;
>> +	u32 frame_ctr;
>> +	union {
>> +		struct {
>> +			u16 pan_id;
>> +			u16 short_addr;
>> +		} pan;
>> +		u8 hw[IEEE802154_ADDR_LEN];
>> +	} key_source;
>> +	u8 key_id;
>> +};
>> +
>> +struct ieee802154_hdr {
>> +	u16 fc;
>> +	u8 seq;
>> +	struct ieee802154_addr source;
>> +	struct ieee802154_addr dest;
>> +	struct ieee802154_sechdr sec;
>> +};
>
> You're going to have to address endianness both in these structure
> definitions and the code.
>
> For types larger than u8 you'll need to use __be16, __le16, __be32,
> __le32 etc. as appropriate.
>
> When setting/loading values, you'll need to use cpu_to_be16(),
> cpu_to_le16() etc.  as appropriate.

The fc field in struct ieee802154_hdr is a bitfield with many subfields,
the sc field of struct ieee802154_sec_hdr is also a bitfield. Would it be
acceptable to represent them as bitfields in the header struct? I expect
the code to be just as efficient in every respect, but more readable since
we wouldn't need explicit shifts and masks everywhere.

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