Now that I'm playing with patch 14, I took more interest in this code.
On Thu, 27 Feb 2020 16:19:59 +0200
"Tzvetomir Stoyanov (VMware)" <tz.stoyanov@xxxxxxxxx> wrote:
> +
> +#define PROTO_MASK_SIZE (sizeof(char))
Hmm, this is the size in bytes of the mask, not bits. You may need both.
#define PROTO_MASK_BITS (PROTO_MASK_SIZE * 8)
Because we can have up to 8 protocols per mask size (8 bits in a byte).
> +/**
> + * tracecmd_tsync_proto_select - Select time sync protocol, to be used for
> + * timestamp synchronization with a peer
> + *
> + * @proto_mask: bitmask array of time sync protocols, supported by the peer
> + * @length: size of the @protos array
> + *
> + * Retuns Id of a time sync protocol, that can be used with the peer, or 0
> + * in case there is no match with supported protocols
> + */
> +unsigned int tracecmd_tsync_proto_select(char *proto_mask, int length)
> +{
> + struct tsync_proto *selected = NULL;
> + struct tsync_proto *proto;
> + int word;
> + int id;
> +
> + for (word = 0; word < length; word++) {
> + for (proto = tsync_proto_list; proto; proto = proto->next) {
> + if (proto->proto_id < word * PROTO_MASK_SIZE)
> + continue;
The above should be: proto->proto_id < word * PROTO_MASK_BITS
Because what you have currently is:
proto->proto_id < word * 1
> +
> + id = proto->proto_id - word * PROTO_MASK_SIZE;
And here you want PROTO_MASK_BITS, otherwise if we have a proto_id of 2
(which would fit as a bit in a char), this would become:
id = 2 - 0 * 1 = 1
> + if (id >= PROTO_MASK_SIZE)
Then this is: 2 >= 1 which would skip it.
Hmm, maybe you don't even need PROTO_MASK_SIZE and only need
PROTO_MASK_BITS.
-- Steve
> + continue;
> +
> + if ((1 << id) & proto_mask[word]) {
> + if (selected) {
> + if (selected->weight < proto->weight)
> + selected = proto;
> + } else
> + selected = proto;
> + }
> + }
> + }
> +
> + if (selected)
> + return selected->proto_id;
> +
> + return 0;
> +}
> +
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