* usbnet with NAPI
@ 2011-04-15 13:05 Michael Riesch
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From: Michael Riesch @ 2011-04-15 13:05 UTC (permalink / raw)
To: netdev; +Cc: David Miller
Habidere,
it looks like the usbnet (on which asix.c bases -> I am still working
on the driver for the Asix AX88172A[1]) does not use NAPI. It
processes the data it receives via netif_rx(). The NAPI way would be
netif_receive_skb in a poll function. Now I would like to check
whether the incoming packets are PTP status frames. My problem is that
skb_defer_rx_timestamp (the PTP check is executed there -
net/core/timestamping.c) is called by netif_receive_skb, but it is not
called by netif_rx(). So the crude hack would be to call
skb_defer_rx_timestamp from the netif_rx() in usbnet.
(It caused the whole system to hang after a few minutes of operation,
so I declared it crude. Haven't found the exact reason for this
behaviour, though...)
The nicer way would probably be enabling usbnet to use NAPI. Now:
- Is or was there some thinking about usbnet going NAPI? In case of
the latter, what was the reason that it was not done? (I could not
find any discussion about that topic)
- Do you see problems doing so? I have read some documentation about
NAPI [2], the requirements seem to be a DMA ring and the ability to
turn off interrupts/events that send packets up the stack.
- Who is going to maintain usbnet in the future?
Looking forward to your comments/ideas,
Michael
[1] http://marc.info/?l=linux-netdev&m=130167000017199&w=2
[2] http://www.linuxfoundation.org/collaborate/workgroups/networking/napi
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