Subject: Re: [PATCH v4 2/9] ptp: Add generic ptp message type function

From: Kurt Kanzenbach <[email-masked]>
Date: Wed, 19 Aug 2020 07:50:25 +0200

On Tue Aug 18 2020, Russell King wrote:
> On Tue, Aug 18, 2020 at 12:32:44PM +0200, Kurt Kanzenbach wrote:
>> The message type is located at different offsets within the ptp header depending
>> on the ptp version (v1 or v2). Therefore, drivers which also deal with ptp v1
>> have some code for it.
>> 
>> Extract this into a helper function for drivers to be used.
>> 
>> Signed-off-by: Kurt Kanzenbach <[email-masked]>
>> Reviewed-by: Richard Cochran <[email-masked]>
>> Reviewed-by: Florian Fainelli <[email-masked]>
>> ---
>>  include/linux/ptp_classify.h | 25 +++++++++++++++++++++++++
>>  1 file changed, 25 insertions(+)
>> 
>> diff --git a/include/linux/ptp_classify.h b/include/linux/ptp_classify.h
>> index 996f31e8f35d..39bad015d1d6 100644
>> --- a/include/linux/ptp_classify.h
>> +++ b/include/linux/ptp_classify.h
>> @@ -96,6 +96,31 @@ unsigned int ptp_classify_raw(const struct sk_buff *skb);
>>   */
>>  struct ptp_header *ptp_parse_header(struct sk_buff *skb, unsigned int type);
>>  
>> +/**
>> + * ptp_get_msgtype - Extract ptp message type from given header
>> + * @hdr: ptp header
>> + * @type: type of the packet (see ptp_classify_raw())
>> + *
>> + * This function returns the message type for a given ptp header. It takes care
>> + * of the different ptp header versions (v1 or v2).
>> + *
>> + * Return: The message type
>> + */
>> +static inline u8 ptp_get_msgtype(const struct ptp_header *hdr,
>> +				 unsigned int type)
>> +{
>> +	u8 msgtype;
>> +
>> +	if (unlikely(type & PTP_CLASS_V1)) {
>> +		/* msg type is located at the control field for ptp v1 */
>> +		msgtype = hdr->control;
>> +	} else {
>> +		msgtype = hdr->tsmt & 0x0f;
>> +	}
>> +
>> +	return msgtype;
>> +}
>
> Are there 256 different message types in V1?

There are only a few messages in PTP V1. But, the control field which
indicates the message type is a byte whereas in PTP v2 it's a nibble.

Thanks,
Kurt