Messages in this thread | | | Subject | RE: [PATCH v3 06/10] net/macb: clean up ring buffer logic | Date | Wed, 31 Oct 2012 08:57:43 -0000 | From | "David Laight" <> |
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> On Tue, Oct 30, 2012 at 4:12 AM, David Laight <David.Laight@aculab.com> wrote: > >> 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. > > ... > >> +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
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