RE: [md-accel PATCH 16/19] dmaengine: driver for the iop32x, iop33x, and iop13xx raid engines

Williams, Dan J
2007-08-27T19:31:37Z

> From: saeed bishara [mailto:saeed.bishara@gmail.com]
> Hi Dan,
> I think you have a bug in this function, the list_splice_init adds the
> new slots in the head of the chain_node, but you get the
> old_chain_tail (latest descriptor) from the tail of the chain!!
>
> > +static dma_cookie_t
> > +iop_adma_tx_submit(struct dma_async_tx_descriptor *tx)
> > +{
> > +
> > + old_chain_tail = list_entry(iop_chan->chain.prev,
> > + struct iop_adma_desc_slot, chain_node);
> > + list_splice_init(&sw_desc->group_list, &old_chain_tail-
> >chain_node);
> > +
> > + /* fix up the hardware chain */
> > + iop_desc_set_next_desc(old_chain_tail, grp_start->phys);
> > +
[ dropped akpm, davem, jeff, and chris from the cc ]

This looks ok to me. &sw_desc->group_list is the head of a new list of
descriptors to be added to the chain. old_chain_tail is youngest
descriptor at the end of the current channel chain.

Before list_splice_init:
old_chain_tail->next = channel_chain_head
channel_chain_head->prev = old_chain_tail
new_chain_start->prev = sw_desc->group_list;
new_chain_end->next = sw_desc->group_list;

After list_splice_init:
new_chain_start->prev = old_chain_tail
old_chain_tail->next = new_chain_start
new_chain_end->next = channel_chain_head
channel_chain_head->prev = new_chain_end

sw_desc->group_list is empty

--
Dan