€•C      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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$]”h&]”Œ	xml:space”Œpreserve”uh1h¡hhhžhhŸŒ?/var/lib/git/docbuild/linux/Documentation/networking/driver.rst”h KubhŒsection”“”)”}”(hhh]”(hŒtitle”“”)”}”(hŒSoftnet Driver Issues”h]”hŒSoftnet Driver Issues”…””}”(hh»hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h¹hh¶hžhhŸh³h Kubhµ)”}”(hhh]”(hº)”}”(hŒProbing guidelines”h]”hŒProbing guidelines”…””}”(hhÌhžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h¹hhÉhžhhŸh³h Kubhµ)”}”(hhh]”(hº)”}”(hŒAddress validation”h]”hŒAddress validation”…””}”(hhÝhžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h¹hhÚhžhhŸh³h 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híhžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hëhŸh³h KhhÚhžhubeh}”(h]”Œaddress-validation”ah ]”h"]”Œaddress validation”ah$]”h&]”uh1h´hhÉhžhhŸh³h Kubeh}”(h]”Œprobing-guidelines”ah ]”h"]”Œprobing guidelines”ah$]”h&]”uh1h´hh¶hžhhŸh³h Kubhµ)”}”(hhh]”(hº)”}”(hŒClose/stop guidelines”h]”hŒClose/stop guidelines”…””}”(hj  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h¹hj  hžhhŸh³h Kubhµ)”}”(hhh]”(hº)”}”(hŒ
Quiescence”h]”hŒ
Quiescence”…””}”(hj  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h¹hj  hžhhŸh³h Kubhì)”}”(hŒÈAfter the ndo_stop routine has been called, the hardware must
not receive or transmit any data.  All in flight packets must
be aborted. If necessary, poll or wait for completion of
any reset commands.”h]”hŒÈAfter the ndo_stop routine has been called, the hardware must
not receive or transmit any data.  All in flight packets must
be aborted. If necessary, poll or wait for completion of
any reset commands.”…””}”(hj-  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hëhŸh³h Khj  hžhubeh}”(h]”Œ
quiescence”ah ]”h"]”Œ
quiescence”ah$]”h&]”uh1h´hj  hžhhŸh³h Kubhµ)”}”(hhh]”(hº)”}”(hŒ
Auto-close”h]”hŒ
Auto-close”…””}”(hjF  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h¹hjC  hžhhŸh³h Kubhì)”}”(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jT  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hëhŸh³h KhjC  hžhubeh}”(h]”Œ
auto-close”ah ]”h"]”Œ
auto-close”ah$]”h&]”uh1h´hj  hžhhŸh³h Kubeh}”(h]”Œclose-stop-guidelines”ah ]”h"]”Œclose/stop guidelines”ah$]”h&]”uh1h´hh¶hžhhŸh³h Kubhµ)”}”(hhh]”(hº)”}”(hŒTransmit path guidelines”h]”hŒTransmit path guidelines”…””}”(hju  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h¹hjr  hžhhŸh³h K#ubhµ)”}”(hhh]”(hº)”}”(hŒStop queues in advance”h]”hŒStop queues in advance”…””}”(hj†  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h¹hjƒ  hžhhŸh³h K&ubhì)”}”(hŒÞThe ndo_start_xmit method must not return NETDEV_TX_BUSY under
any normal circumstances.  It is considered a hard error unless
there is no way your device can tell ahead of time when its
transmit function will become busy.”h]”hŒÞThe ndo_start_xmit method must not return NETDEV_TX_BUSY under
any normal circumstances.  It is considered a hard error unless
there is no way your device can tell ahead of time when its
transmit function will become busy.”…””}”(hj”  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hëhŸh³h K(hjƒ  hžhubhì)”}”(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¢  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hëhŸh³h K-hjƒ  hžhubh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j²  sbah}”(h]”h ]”h"]”h$]”h&]”h±h²Œforce”‰Œlanguage”Œc”Œhighlight_args”}”uh1j°  hŸh³h K0hjƒ  hžhubhì)”}”(hŒ:And then at the end of your TX reclamation event handling:”h]”hŒ:And then at the end of your TX reclamation event handling:”…””}”(hjÅ  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hëhŸh³h K[hjƒ  hžhubj±  )”}”(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jÓ  sbah}”(h]”h ]”h"]”h$]”h&]”h±h²jÀ  ‰jÁ  jÂ  jÃ  }”uh1j°  hŸh³h K]hjƒ  hžhubhµ)”}”(hhh]”(hº)”}”(hŒ(Lockless queue stop / wake helper macros”h]”hŒ(Lockless queue stop / wake helper macros”…””}”(hjå  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h¹hjâ  hžhhŸh³h Keubhì)”}”(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jó  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hëhŸŒ^/var/lib/git/docbuild/linux/Documentation/networking/driver:103: ./include/net/netdev_queues.h”h KŽhjâ  hžhubhì)”}”(hX  We assume that there can be no concurrent stop attempts and no concurrent
wake attempts. The try-stop should happen from the xmit handler,
while wake up should be triggered from NAPI poll context.
The two may run concurrently (single producer, single consumer).”h]”hX  We assume that there can be no concurrent stop attempts and no concurrent
wake attempts. The try-stop should happen from the xmit handler,
while wake up should be triggered from NAPI poll context.
The two may run concurrently (single producer, single consumer).”…””}”(hj  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hëhŸŒ^/var/lib/git/docbuild/linux/Documentation/networking/driver:103: ./include/net/netdev_queues.h”h K’hjâ  hžhubhì)”}”(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  hžhhŸNh NubhŒliteral”“”)”}”(hŒ``stop``”h]”hŒstop”…””}”(hj  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1j  hj  ubhŒ‘ macros outside of the xmit
handler may lead to xmit queue being enabled but not run.
The waking side does not have similar context restrictions.”…””}”(hj  hžhhŸNh Nubeh}”(h]”h ]”h"]”h$]”h&]”uh1hëhŸŒ^/var/lib/git/docbuild/linux/Documentation/networking/driver:103: ./include/net/netdev_queues.h”h K—hjâ  hžhubhì)”}”(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j4  hžhhŸNh NubhŒemphasis”“”)”}”(hŒ*not*”h]”hŒnot”…””}”(hj>  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1j<  hj4  ubhŒt prevent false wake ups when
the ring is full! Drivers should check for ring full at the start
for the xmit handler.”…””}”(hj4  hžhhŸNh Nubeh}”(h]”h ]”h"]”h$]”h&]”uh1hëhŸŒ^/var/lib/git/docbuild/linux/Documentation/networking/driver:103: ./include/net/netdev_queues.h”h Khjâ  hžhubhì)”}”(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jW  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hëhŸŒ^/var/lib/git/docbuild/linux/Documentation/networking/driver:103: ./include/net/netdev_queues.h”h K¢hjâ  hžhubeh}”(h]”Œ&lockless-queue-stop-wake-helper-macros”ah ]”h"]”Œ(lockless queue stop / wake helper macros”ah$]”h&]”uh1h´hjƒ  hžhhŸh³h Keubeh}”(h]”Œstop-queues-in-advance”ah ]”h"]”Œstop queues in advance”ah$]”h&]”uh1h´hjr  hžhhŸh³h K&ubhµ)”}”(hhh]”(hº)”}”(hŒNo exclusive ownership”h]”hŒNo exclusive ownership”…””}”(hjy  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h¹hjv  hžhhŸh³h Kkubhì)”}”(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‡  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hëhŸh³h Kmhjv  hžhubeh}”(h]”Œno-exclusive-ownership”ah ]”h"]”Œno exclusive ownership”ah$]”h&]”uh1h´hjr  hžhhŸh³h Kkubhµ)”}”(hhh]”(hº)”}”(hŒTimely completions”h]”hŒTimely completions”…””}”(hj   hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h¹hj  hžhhŸh³h Kqubhì)”}”(hŒ©Do not forget that once you return NETDEV_TX_OK from your
ndo_start_xmit method, it is your driver's responsibility to free
up the SKB and in some finite amount of time.”h]”hŒ«Do not forget that once you return NETDEV_TX_OK from your
ndo_start_xmit method, it is your driverâ€™s responsibility to free
up the SKB and in some finite amount of time.”…””}”(hj®  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hëhŸh³h Kshj  hžhubhì)”}”(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j¼  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hëhŸh³h Kwhj  hžhubhì)”}”(hŒIf you return NETDEV_TX_BUSY from the ndo_start_xmit method, you
must not keep any reference to that SKB and you must not attempt
to free it up.”h]”hŒIf you return NETDEV_TX_BUSY from the ndo_start_xmit method, you
must not keep any reference to that SKB and you must not attempt
to free it up.”…””}”(hjÊ  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hëhŸh³h K}hj  hžhubeh}”(h]”Œtimely-completions”ah ]”h"]”Œtimely completions”ah$]”h&]”uh1h´hjr  hžhhŸh³h Kqubeh}”(h]”Œtransmit-path-guidelines”ah ]”h"]”Œtransmit path guidelines”ah$]”h&]”uh1h´hh¶hžhhŸh³h K#ubeh}”(h]”Œsoftnet-driver-issues”ah ]”h"]”Œsoftnet driver issues”ah$]”h&]”uh1h´hhhžhhŸh³h Kubeh}”(h]”h ]”h"]”h$]”h&]”Œsource”h³uh1hŒcurrent_source”NŒcurrent_line”NŒsettings”Œdocutils.frontend”ŒValues”“”)”}”(h¹NŒ	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
halt_level”KŒexit_status_level”KŒdebug”NŒwarning_stream”NŒ	traceback”ˆŒinput_encoding”Œ	utf-8-sig”Œinput_encoding_error_handler”Œstrict”Œoutput_encoding”Œutf-8”Œoutput_encoding_error_handler”j  Œerror_encoding”Œutf-8”Œerror_encoding_error_handler”Œbackslashreplace”Œlanguage_code”Œen”Œrecord_dependencies”NŒconfig”NŒ	id_prefix”hŒauto_id_prefix”Œid”Œdump_settings”NŒdump_internals”NŒdump_transforms”NŒdump_pseudo_xml”NŒexpose_internals”NŒstrict_visitor”NŒ_disable_config”NŒ_source”h³Œ_destination”NŒ_config_files”]”Œ7/var/lib/git/docbuild/linux/Documentation/docutils.conf”aŒfile_insertion_enabled”ˆŒraw_enabled”KŒline_length_limit”M'Œpep_references”NŒpep_base_url”Œhttps://peps.python.org/”Œpep_file_url_template”Œpep-%04d”Œrfc_references”NŒrfc_base_url”Œ&https://datatracker.ietf.org/doc/html/”Œ	tab_width”KŒtrim_footnote_reference_space”‰Œsyntax_highlight”Œlong”Œsmart_quotes”ˆŒsmartquotes_locales”]”Œcharacter_level_inline_markup”‰Œdoctitle_xform”‰Œdocinfo_xform”KŒsectsubtitle_xform”‰Œimage_loading”Œlink”Œembed_stylesheet”‰Œcloak_email_addresses”ˆŒsection_self_link”‰Œenv”NubŒreporter”NŒindirect_targets”]”Œsubstitution_defs”}”Œsubstitution_names”}”Œrefnames”}”Œrefids”}”Œnameids”}”(jí  jê  j  j  j   hýjo  jl  j@  j=  jg  jd  jå  jâ  js  jp  jk  jh  jš  j—  jÝ  jÚ  uŒ	nametypes”}”(jí  ‰j  ‰j   ‰jo  ‰j@  ‰jg  ‰jå  ‰js  ‰jk  ‰jš  ‰jÝ  ‰uh}”(jê  h¶j  hÉhýhÚjl  j  j=  j  jd  jC  jâ  jr  jp  jƒ  jh  jâ  j—  jv  jÚ  j  uŒfootnote_refs”}”Œcitation_refs”}”Œautofootnotes”]”Œautofootnote_refs”]”Œsymbol_footnotes”]”Œsymbol_footnote_refs”]”Œ	footnotes”]”Œ	citations”]”Œautofootnote_start”KŒsymbol_footnote_start”K Œ
id_counter”Œcollections”ŒCounter”“”}”…”R”Œparse_messages”]”Œtransform_messages”]”Œtransformer”NŒinclude_log”]”Œ
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