RE: [PATCH v3 06/10] net/macb: clean up ring buffer logic

On Tue, Oct 30, 2012 at 4:12 AM, David Laight [off-list ref] wrote:

quoted

quoted

Instead of masking head and tail every time we increment them, just let them
wrap through UINT_MAX and mask them when subscripting. Add simple accessor
functions to do the subscripting properly to minimize the chances of messing
this up.

...

quoted

+static unsigned int macb_tx_ring_avail(struct macb *bp)
+{
+     return TX_RING_SIZE - (bp->tx_head - bp->tx_tail);
+}

That one doesn't look quite right to me.
Surely it should be masking with 'TX_RING_SIZE - 1'

Why is that? head and tail can never be more than TX_RING_SIZE apart,
so it shouldn't make any difference.

It's a ring buffer (I presume) the pointers can be in either order.

	David