linux/net/dsa
Vladimir Oltean a2c65a9d05 net: dsa: fall back to default tagger if we can't load the one from DT
DSA tagging protocol drivers can be changed at runtime through sysfs and
at probe time through the device tree (support for the latter was added
later).

When changing through sysfs, it is assumed that the module for the new
tagging protocol was already loaded into the kernel (in fact this is
only a concern for Ocelot/Felix switches, where we have tag_ocelot.ko
and tag_ocelot_8021q.ko; for every other switch, the default and
alternative protocols are compiled within the same .ko, so there is
nothing for the user to load).

The kernel cannot currently call request_module(), because it has no way
of constructing the modalias name of the tagging protocol driver
("dsa_tag-%d", where the number is one of DSA_TAG_PROTO_*_VALUE).
The device tree only contains the string name of the tagging protocol
("ocelot-8021q"), and the only mapping between the string and the
DSA_TAG_PROTO_OCELOT_8021Q_VALUE is present in tag_ocelot_8021q.ko.
So this is a chicken-and-egg situation and dsa_core.ko has nothing based
on which it can automatically request the insertion of the module.

As a consequence, if CONFIG_NET_DSA_TAG_OCELOT_8021Q is built as module,
the switch will forever defer probing.

The long-term solution is to make DSA call request_module() somehow,
but that probably needs some refactoring.

What we can do to keep operating with existing device tree blobs is to
cancel the attempt to change the tagging protocol with the one specified
there, and to remain operating with the default one. Depending on the
situation, the default protocol might still allow some functionality
(in the case of ocelot, it does), and it's better to have that than to
fail to probe.

Fixes: deff710703 ("net: dsa: Allow default tag protocol to be overridden from DT")
Link: https://lore.kernel.org/lkml/20221027113248.420216-1-michael@walle.cc/
Reported-by: Heiko Thiery <heiko.thiery@gmail.com>
Reported-by: Michael Walle <michael@walle.cc>
Signed-off-by: Vladimir Oltean <vladimir.oltean@nxp.com>
Tested-by: Michael Walle <michael@walle.cc>
Reviewed-by: Florian Fainelli <f.fainelli@gmail.com>
Link: https://lore.kernel.org/r/20221027145439.3086017-1-vladimir.oltean@nxp.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
2022-10-28 21:58:30 -07:00
..
dsa2.c net: dsa: fall back to default tagger if we can't load the one from DT 2022-10-28 21:58:30 -07:00
dsa_priv.h net: dsa: don't leave dangling pointers in dp->pl when failing 2022-09-30 18:17:16 -07:00
dsa.c net: dsa: allow the DSA master to be seen and changed through rtnetlink 2022-09-20 10:32:35 +02:00
Kconfig net: dsa: tag_ksz: add tag handling for Microchip LAN937x 2022-07-02 16:34:05 +01:00
Makefile net: dsa: allow the DSA master to be seen and changed through rtnetlink 2022-09-20 10:32:35 +02:00
master.c net: dsa: allow masters to join a LAG 2022-09-20 10:32:36 +02:00
netlink.c net: dsa: make user ports return to init_net on netns deletion 2022-09-26 11:28:57 -07:00
port.c net: dsa: fix wrong pointer passed to PTR_ERR() in dsa_port_phylink_create() 2022-10-09 20:01:32 +01:00
slave.c net: dsa: uninitialized variable in dsa_slave_netdevice_event() 2022-10-15 11:15:27 +01:00
switch.c net: dsa: allow masters to join a LAG 2022-09-20 10:32:36 +02:00
tag_8021q.c net: dsa: introduce dsa_port_get_master() 2022-09-20 10:32:35 +02:00
tag_ar9331.c net: dsa: remove the struct packet_type argument from dsa_device_ops::rcv() 2021-08-02 15:13:15 +01:00
tag_brcm.c net: dsa: Fix spelling mistakes and cleanup code 2022-08-01 12:23:06 -07:00
tag_dsa.c net: dsa: tag_dsa: Fix tx from VLAN uppers on non-filtering bridges 2022-03-08 11:12:28 +01:00
tag_gswip.c net: dsa: remove the struct packet_type argument from dsa_device_ops::rcv() 2021-08-02 15:13:15 +01:00
tag_hellcreek.c net: dsa: hellcreek: Print warning only once 2022-08-31 19:54:04 -07:00
tag_ksz.c net: dsa: tag_ksz: add tag handling for Microchip LAN937x 2022-07-02 16:34:05 +01:00
tag_lan9303.c net: dsa: lan9303: handle hwaccel VLAN tags 2022-02-17 09:32:06 -08:00
tag_mtk.c net: dsa: create a helper for locating EtherType DSA headers on TX 2021-08-11 14:44:58 +01:00
tag_ocelot_8021q.c net: dsa: tag_8021q: merge RX and TX VLANs 2022-02-27 11:06:14 +00:00
tag_ocelot.c Merge git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net 2021-12-23 16:09:58 -08:00
tag_qca.c net: dsa: tag_qca: add support for handling mgmt and MIB Ethernet packet 2022-02-02 14:43:59 +00:00
tag_rtl4_a.c net: dsa: tag_rtl4_a: Drop bit 9 from egress frames 2021-09-14 19:34:03 -07:00
tag_rtl8_4.c net: dsa: tag_rtl8_4: fix typo in modalias name 2022-03-09 20:36:24 -08:00
tag_rzn1_a5psw.c net: dsa: add Renesas RZ/N1 switch tag driver 2022-06-27 11:37:55 +01:00
tag_sja1105.c net: dsa: tag_8021q: rename dsa_8021q_bridge_tx_fwd_offload_vid 2022-02-27 11:06:14 +00:00
tag_trailer.c net: dsa: remove the struct packet_type argument from dsa_device_ops::rcv() 2021-08-02 15:13:15 +01:00
tag_xrs700x.c net: dsa: remove the struct packet_type argument from dsa_device_ops::rcv() 2021-08-02 15:13:15 +01:00