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Date: Sun, 05 Oct 2014 17:07:36 -0700 From: John Fastabend <john.fastabend@...il.com> To: dborkman@...hat.com, fw@...len.de, gerlitz.or@...il.com, hannes@...essinduktion.org Cc: netdev@...r.kernel.org, john.ronciak@...el.com, amirv@...lanox.com, eric.dumazet@...il.com, danny.zhou@...el.com Subject: [net-next PATCH v1 3/3] net: packet: Document PACKET_DEV_QPAIR_SPLIT and friends This adds a section to the packet interface kernel documentation describing the set of socket options to get direct queue assignment working. Signed-off-by: John Fastabend <john.r.fastabend@...el.com> --- Documentation/networking/packet_mmap.txt | 44 ++++++++++++++++++++++++++++++ 1 file changed, 44 insertions(+) diff --git a/Documentation/networking/packet_mmap.txt b/Documentation/networking/packet_mmap.txt index a6d7cb9..ad26194 100644 --- a/Documentation/networking/packet_mmap.txt +++ b/Documentation/networking/packet_mmap.txt @@ -1047,6 +1047,50 @@ See include/linux/net_tstamp.h and Documentation/networking/timestamping for more information on hardware timestamps. ------------------------------------------------------------------------------- ++ PACKET_RXTX_QPAIRS_SPLIT and friends +------------------------------------------------------------------------------- + +The PACKET_RXTX_QPAIRS_SLIT setting allows direct access to the hardware +packet rings. If your NIC is capable of supporting hardware packet steering +and the driver has this feature enabled you can use the hardware to steer +packets directly to user mapped memory and use user space descriptor rings. + +The user space flow should be, + + bind(fd, &sockaddr, sizeof(sockaddr)); + + /* Get the device type and info */ + getsockopt(fd, SOL_PACKET, PACKET_DEV_DESC_INFO, &def_info, + &optlen); + + /* With device info we can look up descriptor format */ + + /* Get the layout of ring space offset, page_sz, cnt */ + getsockopt(fd, SOL_PACKET, PACKET_DEV_QPAIR_MAP_REGION_INFO, + &info, &optlen); + + /* request some queues from the driver */ + setsockopt(fd, SOL_PACKET, PACKET_RXTX_QPAIRS_SPLIT, + &qpairs_info, sizeof(qpairs_info)); + + /* if we let the driver pick us queues learn which queues + * we were given + */ + getsockopt(fd, SOL_PACKET, PACKET_RXTX_QPAIRS_SPLIT, + &qpairs_info, sizeof(qpairs_info)); + + /* And mmap queue pairs to user space */ + mmap(NULL, info.tp_dev_bar_sz, PROT_READ | PROT_WRITE, + MAP_SHARED, fd, 0); + + /* Now we have some user space queues to read/write to*/ + +After this user space can directly manipulate the drivers descriptor rings. +The descriptor rings use the native descriptor format of the hardware device. +The device specifics are returned from the PACKET_DEV_DESC_INFO call which +allows user space to determine the correct descriptor format to use. + +------------------------------------------------------------------------------- + Miscellaneous bits ------------------------------------------------------------------------------- -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
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