€•D      Œsphinx.addnodes”Œdocument”“”)”}”(Œ	rawsource”Œ ”Œchildren”]”(Œtranslations”ŒLanguagesNode”“”)”}”(hhh]”(h Œpending_xref”“”)”}”(hhh]”Œdocutils.nodes”ŒText”“”ŒChinese (Simplified)”…””}”Œparent”hsbaŒ
attributes”}”(Œids”]”Œclasses”]”Œnames”]”Œdupnames”]”Œbackrefs”]”Œ	refdomain”Œstd”Œreftype”Œdoc”Œ	reftarget”Œ%/translations/zh_CN/networking/driver”Œmodname”NŒ	classname”NŒrefexplicit”ˆuŒtagname”hhhubh)”}”(hhh]”hŒChinese (Traditional)”…””}”hh2sbah}”(h]”h ]”h"]”h$]”h&]”Œ	refdomain”h)Œreftype”h+Œ	reftarget”Œ%/translations/zh_TW/networking/driver”Œmodname”NŒ	classname”NŒrefexplicit”ˆuh1hhhubh)”}”(hhh]”hŒItalian”…””}”hhFsbah}”(h]”h ]”h"]”h$]”h&]”Œ	refdomain”h)Œreftype”h+Œ	reftarget”Œ%/translations/it_IT/networking/driver”Œmodname”NŒ	classname”NŒrefexplicit”ˆuh1hhhubh)”}”(hhh]”hŒJapanese”…””}”hhZsbah}”(h]”h ]”h"]”h$]”h&]”Œ	refdomain”h)Œreftype”h+Œ	reftarget”Œ%/translations/ja_JP/networking/driver”Œmodname”NŒ	classname”NŒrefexplicit”ˆuh1hhhubh)”}”(hhh]”hŒKorean”…””}”hhnsbah}”(h]”h ]”h"]”h$]”h&]”Œ	refdomain”h)Œreftype”h+Œ	reftarget”Œ%/translations/ko_KR/networking/driver”Œmodname”NŒ	classname”NŒrefexplicit”ˆuh1hhhubh)”}”(hhh]”hŒPortuguese (Brazilian)”…””}”hh‚sbah}”(h]”h ]”h"]”h$]”h&]”Œ	refdomain”h)Œreftype”h+Œ	reftarget”Œ%/translations/pt_BR/networking/driver”Œmodname”NŒ	classname”NŒrefexplicit”ˆuh1hhhubh)”}”(hhh]”hŒSpanish”…””}”hh–sbah}”(h]”h ]”h"]”h$]”h&]”Œ	refdomain”h)Œreftype”h+Œ	reftarget”Œ%/translations/sp_SP/networking/driver”Œmodname”NŒ	classname”NŒrefexplicit”ˆuh1hhhubeh}”(h]”h ]”h"]”h$]”h&]”Œcurrent_language”ŒEnglish”uh1h
hhŒ	_document”hŒsource”NŒline”NubhŒcomment”“”)”}”(hŒ SPDX-License-Identifier: GPL-2.0”h]”hŒ SPDX-License-Identifier: GPL-2.0”…””}”hh·sbah}”(h]”h ]”h"]”h$]”h&]”Œ	xml:space”Œpreserve”uh1hµhhh²hh³Œ?/var/lib/git/docbuild/linux/Documentation/networking/driver.rst”h´KubhŒsection”“”)”}”(hhh]”(hŒtitle”“”)”}”(hŒSoftnet Driver Issues”h]”hŒSoftnet Driver Issues”…””}”(hhÏh²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hÍhhÊh²hh³hÇh´KubhÉ)”}”(hhh]”(hÎ)”}”(hŒProbing guidelines”h]”hŒProbing guidelines”…””}”(hhàh²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hÍhhÝh²hh³hÇh´KubhÉ)”}”(hhh]”(hÎ)”}”(hŒAddress validation”h]”hŒAddress validation”…””}”(hhñh²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hÍhhîh²hh³hÇh´KubhŒ	paragraph”“”)”}”(hŒœAny hardware layer address you obtain for your device should
be verified.  For example, for ethernet check it with
linux/etherdevice.h:is_valid_ether_addr()”h]”hŒœAny hardware layer address you obtain for your device should
be verified.  For example, for ethernet check it with
linux/etherdevice.h:is_valid_ether_addr()”…””}”(hj  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hÿh³hÇh´Khhîh²hubeh}”(h]”Œaddress-validation”ah ]”h"]”Œaddress validation”ah$]”h&]”uh1hÈhhÝh²hh³hÇh´Kubeh}”(h]”Œprobing-guidelines”ah ]”h"]”Œprobing guidelines”ah$]”h&]”uh1hÈhhÊh²hh³hÇh´KubhÉ)”}”(hhh]”(hÎ)”}”(hŒClose/stop guidelines”h]”hŒClose/stop guidelines”…””}”(hj"  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hÍhj  h²hh³hÇh´KubhÉ)”}”(hhh]”(hÎ)”}”(hŒ
Quiescence”h]”hŒ
Quiescence”…””}”(hj3  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hÍhj0  h²hh³hÇh´Kubj   )”}”(hŒÈAfter the ndo_stop routine has been called, the hardware must
not receive or transmit any data.  All in flight packets must
be aborted. If necessary, poll or wait for completion of
any reset commands.”h]”hŒÈAfter the ndo_stop routine has been called, the hardware must
not receive or transmit any data.  All in flight packets must
be aborted. If necessary, poll or wait for completion of
any reset commands.”…””}”(hjA  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hÿh³hÇh´Khj0  h²hubeh}”(h]”Œ
quiescence”ah ]”h"]”Œ
quiescence”ah$]”h&]”uh1hÈhj  h²hh³hÇh´KubhÉ)”}”(hhh]”(hÎ)”}”(hŒ
Auto-close”h]”hŒ
Auto-close”…””}”(hjZ  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hÍhjW  h²hh³hÇh´Kubj   )”}”(hŒRThe ndo_stop routine will be called by unregister_netdevice
if device is still UP.”h]”hŒRThe ndo_stop routine will be called by unregister_netdevice
if device is still UP.”…””}”(hjh  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hÿh³hÇh´KhjW  h²hubeh}”(h]”Œ
auto-close”ah ]”h"]”Œ
auto-close”ah$]”h&]”uh1hÈhj  h²hh³hÇh´Kubeh}”(h]”Œclose-stop-guidelines”ah ]”h"]”Œclose/stop guidelines”ah$]”h&]”uh1hÈhhÊh²hh³hÇh´KubhÉ)”}”(hhh]”(hÎ)”}”(hŒTransmit path guidelines”h]”hŒTransmit path guidelines”…””}”(hj‰  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hÍhj†  h²hh³hÇh´K#ubhÉ)”}”(hhh]”(hÎ)”}”(hŒStop queues in advance”h]”hŒStop queues in advance”…””}”(hjš  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hÍhj—  h²hh³hÇh´K&ubj   )”}”(hŒÞThe ndo_start_xmit method must not return NETDEV_TX_BUSY under
any normal circumstances.  It is considered a hard error unless
there is no way your device can tell ahead of time when its
transmit function will become busy.”h]”hŒÞThe ndo_start_xmit method must not return NETDEV_TX_BUSY under
any normal circumstances.  It is considered a hard error unless
there is no way your device can tell ahead of time when its
transmit function will become busy.”…””}”(hj¨  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hÿh³hÇh´K(hj—  h²hubj   )”}”(hŒoInstead it must maintain the queue properly.  For example,
for a driver implementing scatter-gather this means:”h]”hŒoInstead it must maintain the queue properly.  For example,
for a driver implementing scatter-gather this means:”…””}”(hj¶  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hÿh³hÇh´K-hj—  h²hubhŒliteral_block”“”)”}”(hX®  static u32 drv_tx_avail(struct drv_ring *dr)
{
        u32 used = READ_ONCE(dr->prod) - READ_ONCE(dr->cons);

        return dr->tx_ring_size - (used & bp->tx_ring_mask);
}

static netdev_tx_t drv_hard_start_xmit(struct sk_buff *skb,
                                       struct net_device *dev)
{
        struct drv *dp = netdev_priv(dev);
        struct netdev_queue *txq;
        struct drv_ring *dr;
        int idx;

        idx = skb_get_queue_mapping(skb);
        dr = dp->tx_rings[idx];
        txq = netdev_get_tx_queue(dev, idx);

        //...
        /* This should be a very rare race - log it. */
        if (drv_tx_avail(dr) <= skb_shinfo(skb)->nr_frags + 1) {
                netif_stop_queue(dev);
                netdev_warn(dev, "Tx Ring full when queue awake!\n");
                return NETDEV_TX_BUSY;
        }

        //... queue packet to card ...

        netdev_tx_sent_queue(txq, skb->len);

        //... update tx producer index using WRITE_ONCE() ...

        if (!netif_txq_maybe_stop(txq, drv_tx_avail(dr),
                                  MAX_SKB_FRAGS + 1, 2 * MAX_SKB_FRAGS))
                dr->stats.stopped++;

        //...
        return NETDEV_TX_OK;
}”h]”hX®  static u32 drv_tx_avail(struct drv_ring *dr)
{
        u32 used = READ_ONCE(dr->prod) - READ_ONCE(dr->cons);

        return dr->tx_ring_size - (used & bp->tx_ring_mask);
}

static netdev_tx_t drv_hard_start_xmit(struct sk_buff *skb,
                                       struct net_device *dev)
{
        struct drv *dp = netdev_priv(dev);
        struct netdev_queue *txq;
        struct drv_ring *dr;
        int idx;

        idx = skb_get_queue_mapping(skb);
        dr = dp->tx_rings[idx];
        txq = netdev_get_tx_queue(dev, idx);

        //...
        /* This should be a very rare race - log it. */
        if (drv_tx_avail(dr) <= skb_shinfo(skb)->nr_frags + 1) {
                netif_stop_queue(dev);
                netdev_warn(dev, "Tx Ring full when queue awake!\n");
                return NETDEV_TX_BUSY;
        }

        //... queue packet to card ...

        netdev_tx_sent_queue(txq, skb->len);

        //... update tx producer index using WRITE_ONCE() ...

        if (!netif_txq_maybe_stop(txq, drv_tx_avail(dr),
                                  MAX_SKB_FRAGS + 1, 2 * MAX_SKB_FRAGS))
                dr->stats.stopped++;

        //...
        return NETDEV_TX_OK;
}”…””}”hjÆ  sbah}”(h]”h ]”h"]”h$]”h&]”hÅhÆŒforce”‰Œlanguage”Œc”Œhighlight_args”}”uh1jÄ  h³hÇh´K0hj—  h²hubj   )”}”(hŒ:And then at the end of your TX reclamation event handling:”h]”hŒ:And then at the end of your TX reclamation event handling:”…””}”(hjÙ  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hÿh³hÇh´K[hj—  h²hubjÅ  )”}”(hŒª//... update tx consumer index using WRITE_ONCE() ...

netif_txq_completed_wake(txq, cmpl_pkts, cmpl_bytes,
                         drv_tx_avail(dr), 2 * MAX_SKB_FRAGS);”h]”hŒª//... update tx consumer index using WRITE_ONCE() ...

netif_txq_completed_wake(txq, cmpl_pkts, cmpl_bytes,
                         drv_tx_avail(dr), 2 * MAX_SKB_FRAGS);”…””}”hjç  sbah}”(h]”h ]”h"]”h$]”h&]”hÅhÆjÔ  ‰jÕ  jÖ  j×  }”uh1jÄ  h³hÇh´K]hj—  h²hubhÉ)”}”(hhh]”(hÎ)”}”(hŒ(Lockless queue stop / wake helper macros”h]”hŒ(Lockless queue stop / wake helper macros”…””}”(hjù  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hÍhjö  h²hh³hÇh´Keubj   )”}”(hŒ£The netif_txq_maybe_stop() and __netif_txq_completed_wake()
macros are designed to safely implement stopping
and waking netdev queues without full lock protection.”h]”hŒ£The netif_txq_maybe_stop() and __netif_txq_completed_wake()
macros are designed to safely implement stopping
and waking netdev queues without full lock protection.”…””}”(hj  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hÿh³Œ^/var/lib/git/docbuild/linux/Documentation/networking/driver:103: ./include/net/netdev_queues.h”h´KÆhjö  h²hubj   )”}”(hX  We assume that there can be no concurrent stop attempts and no concurrent
wake attempts. The try-stop should happen from the xmit handler,
while wake up should be triggered from NAPI poll context.
The two may run concurrently (single producer, single consumer).”h]”hX  We assume that there can be no concurrent stop attempts and no concurrent
wake attempts. The try-stop should happen from the xmit handler,
while wake up should be triggered from NAPI poll context.
The two may run concurrently (single producer, single consumer).”…””}”(hj  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hÿh³Œ^/var/lib/git/docbuild/linux/Documentation/networking/driver:103: ./include/net/netdev_queues.h”h´KÊhjö  h²hubj   )”}”(hXC  The try-stop side is expected to run from the xmit handler and therefore
it does not reschedule Tx (netif_tx_start_queue() instead of
netif_tx_wake_queue()). Uses of the ``stop`` macros outside of the xmit
handler may lead to xmit queue being enabled but not run.
The waking side does not have similar context restrictions.”h]”(hŒªThe try-stop side is expected to run from the xmit handler and therefore
it does not reschedule Tx (netif_tx_start_queue() instead of
netif_tx_wake_queue()). Uses of the ”…””}”(hj%  h²hh³Nh´NubhŒliteral”“”)”}”(hŒ``stop``”h]”hŒstop”…””}”(hj/  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1j-  hj%  ubhŒ‘ macros outside of the xmit
handler may lead to xmit queue being enabled but not run.
The waking side does not have similar context restrictions.”…””}”(hj%  h²hh³Nh´Nubeh}”(h]”h ]”h"]”h$]”h&]”uh1hÿh³Œ^/var/lib/git/docbuild/linux/Documentation/networking/driver:103: ./include/net/netdev_queues.h”h´KÏhjö  h²hubj   )”}”(hŒÙThe macros guarantee that rings will not remain stopped if there's
space available, but they do *not* prevent false wake ups when
the ring is full! Drivers should check for ring full at the start
for the xmit handler.”h]”(hŒbThe macros guarantee that rings will not remain stopped if thereâ€™s
space available, but they do ”…””}”(hjH  h²hh³Nh´NubhŒemphasis”“”)”}”(hŒ*not*”h]”hŒnot”…””}”(hjR  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1jP  hjH  ubhŒt prevent false wake ups when
the ring is full! Drivers should check for ring full at the start
for the xmit handler.”…””}”(hjH  h²hh³Nh´Nubeh}”(h]”h ]”h"]”h$]”h&]”uh1hÿh³Œ^/var/lib/git/docbuild/linux/Documentation/networking/driver:103: ./include/net/netdev_queues.h”h´KÕhjö  h²hubj   )”}”(hŒiAll descriptor ring indexes (and other relevant shared state) must
be updated before invoking the macros.”h]”hŒiAll descriptor ring indexes (and other relevant shared state) must
be updated before invoking the macros.”…””}”(hjk  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hÿh³Œ^/var/lib/git/docbuild/linux/Documentation/networking/driver:103: ./include/net/netdev_queues.h”h´KÚhjö  h²hubeh}”(h]”Œ&lockless-queue-stop-wake-helper-macros”ah ]”h"]”Œ(lockless queue stop / wake helper macros”ah$]”h&]”uh1hÈhj—  h²hh³hÇh´Keubeh}”(h]”Œstop-queues-in-advance”ah ]”h"]”Œstop queues in advance”ah$]”h&]”uh1hÈhj†  h²hh³hÇh´K&ubhÉ)”}”(hhh]”(hÎ)”}”(hŒNo exclusive ownership”h]”hŒNo exclusive ownership”…””}”(hj  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hÍhjŠ  h²hh³hÇh´Kkubj   )”}”(hŒJAn ndo_start_xmit method must not modify the shared parts of a
cloned SKB.”h]”hŒJAn ndo_start_xmit method must not modify the shared parts of a
cloned SKB.”…””}”(hj›  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hÿh³hÇh´KmhjŠ  h²hubeh}”(h]”Œno-exclusive-ownership”ah ]”h"]”Œno exclusive ownership”ah$]”h&]”uh1hÈhj†  h²hh³hÇh´KkubhÉ)”}”(hhh]”(hÎ)”}”(hŒTimely completions”h]”hŒTimely completions”…””}”(hj´  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hÍhj±  h²hh³hÇh´Kqubj   )”}”(hŒ©Do not forget that once you return NETDEV_TX_OK from your
ndo_start_xmit method, it is your driver's responsibility to free
up the SKB and in some finite amount of time.”h]”hŒ«Do not forget that once you return NETDEV_TX_OK from your
ndo_start_xmit method, it is your driverâ€™s responsibility to free
up the SKB and in some finite amount of time.”…””}”(hjÂ  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hÿh³hÇh´Kshj±  h²hubj   )”}”(hŒøFor example, this means that it is not allowed for your TX
mitigation scheme to let TX packets "hang out" in the TX
ring unreclaimed forever if no new TX packets are sent.
This error can deadlock sockets waiting for send buffer room
to be freed up.”h]”hŒüFor example, this means that it is not allowed for your TX
mitigation scheme to let TX packets â€œhang outâ€ in the TX
ring unreclaimed forever if no new TX packets are sent.
This error can deadlock sockets waiting for send buffer room
to be freed up.”…””}”(hjÐ  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hÿh³hÇh´Kwhj±  h²hubj   )”}”(hŒIf you return NETDEV_TX_BUSY from the ndo_start_xmit method, you
must not keep any reference to that SKB and you must not attempt
to free it up.”h]”hŒIf you return NETDEV_TX_BUSY from the ndo_start_xmit method, you
must not keep any reference to that SKB and you must not attempt
to free it up.”…””}”(hjÞ  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hÿh³hÇh´K}hj±  h²hubeh}”(h]”Œtimely-completions”ah ]”h"]”Œtimely completions”ah$]”h&]”uh1hÈhj†  h²hh³hÇh´Kqubeh}”(h]”Œtransmit-path-guidelines”ah ]”h"]”Œtransmit path guidelines”ah$]”h&]”uh1hÈhhÊh²hh³hÇh´K#ubeh}”(h]”Œsoftnet-driver-issues”ah ]”h"]”Œsoftnet driver issues”ah$]”h&]”uh1hÈhhh²hh³hÇh´Kubeh}”(h]”h ]”h"]”h$]”h&]”Œsource”hÇuh1hŒcurrent_source”NŒcurrent_line”NŒsettings”Œdocutils.frontend”ŒValues”“”)”}”(hÍNŒ	generator”NŒ	datestamp”NŒsource_link”NŒ
source_url”NŒtoc_backlinks”Œentry”Œfootnote_backlinks”KŒsectnum_xform”KŒstrip_comments”NŒstrip_elements_with_classes”NŒstrip_classes”NŒreport_level”KŒ
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