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Author SHA1 Message Date
Rafał Miłecki
89778ba335 usb: core: usbport: Use proper LED API to fix potential crash 
Calling brightness_set manually isn't safe as some LED drivers don't
implement this callback. The best idea is to just use a proper helper
which will fallback to the brightness_set_blocking callback if needed.

This fixes:
[ 1461.761528] Unable to handle kernel NULL pointer dereference at virtual address 00000000
(...)
[ 1462.117049] Backtrace:
[ 1462.119521] [<bf228164>] (usbport_trig_port_store [ledtrig_usbport]) from [<c023f758>] (dev_attr_store+0x20/0x2c)
[ 1462.129826]  r7:dcabc7c0 r6:dee0ff80 r5:00000002 r4:bf228164
[ 1462.135511] [<c023f738>] (dev_attr_store) from [<c0169310>] (sysfs_kf_write+0x48/0x4c)
[ 1462.143459]  r5:00000002 r4:c023f738
[ 1462.147049] [<c01692c8>] (sysfs_kf_write) from [<c0168ab8>] (kernfs_fop_write+0xf8/0x1f8)
[ 1462.155258]  r5:00000002 r4:df4a1000
[ 1462.158850] [<c01689c0>] (kernfs_fop_write) from [<c0100c78>] (__vfs_write+0x34/0x120)
[ 1462.166800]  r10:00000000 r9:dee0e000 r8:c000fc24 r7:00000002 r6:dee0ff80 r5:c01689c0
[ 1462.174660]  r4:df727a80
[ 1462.177204] [<c0100c44>] (__vfs_write) from [<c0101ae4>] (vfs_write+0xac/0x170)
[ 1462.184543]  r9:dee0e000 r8:c000fc24 r7:dee0ff80 r6:b6f092d0 r5:df727a80 r4:00000002
[ 1462.192319] [<c0101a38>] (vfs_write) from [<c01028dc>] (SyS_write+0x4c/0xa8)
[ 1462.199396]  r9:dee0e000 r8:c000fc24 r7:00000002 r6:b6f092d0 r5:df727a80 r4:df727a80
[ 1462.207174] [<c0102890>] (SyS_write) from [<c000fa60>] (ret_fast_syscall+0x0/0x3c)
[ 1462.214774]  r7:00000004 r6:ffffffff r5:00000000 r4:00000000
[ 1462.220456] Code: bad PC value
[ 1462.223560] ---[ end trace 676638a3a12c7a56 ]---

Reported-by: Ralph Sennhauser <ralph.sennhauser@gmail.com>
Signed-off-by: Rafał Miłecki <rafal@milecki.pl>
Fixes: 0f247626cb ("usb: core: Introduce a USB port LED trigger")
Cc: stable@vger.kernel.org # 4.9+
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
 2016-12-06 08:37:41 +01:00
Rafał Miłecki
0f247626cb usb: core: Introduce a USB port LED trigger 
This commit adds a new trigger responsible for turning on LED when USB
device gets connected to the selected USB port. This can can useful for
various home routers that have USB port(s) and a proper LED telling user
a device is connected.

The trigger gets its documentation file but basically it just requires
enabling it and selecting USB ports (e.g. echo 1 > ports/usb1-1).

There was a long discussion on design of this driver. Its current state
is a result of picking them most adjustable solution as others couldn't
handle all cases.

1) It wasn't possible for the driver to register separated trigger for
   each USB port. Some physical USB ports are handled by more than one
   controller and so by more than one USB port. E.g. USB 2.0 physical
   port may be handled by OHCI's port and EHCI's port.
   It's also not possible to assign more than 1 trigger to a single LED
   and implementing such feature would be tricky due to syncing triggers
   and sysfs conflicts with old triggers.

2) Another idea was to register trigger per USB hub. This wouldn't allow
   handling devices with multiple USB LEDs and controllers (hubs)
   controlling more than 1 physical port. It's common for hubs to have
   few ports and each may have its own LED.

This final trigger is highly flexible. It allows selecting any USB ports
for any LED. It was also modified (comparing to the initial version) to
allow choosing ports rather than having user /guess/ proper names. It
was successfully tested on SmartRG SR400ac which has 3 USB LEDs,
2 physical ports and 3 controllers.

It was noted USB subsystem already has usb-gadget and usb-host triggers
but they are pretty trivial ones. They indicate activity only and can't
have ports specified.

In future it may be good idea to consider adding activity support to
usbport as well. This should allow switching to this more generic driver
and maybe marking old ones as obsolete.
This can be implemented with another sysfs file for setting mode. The
default mode wouldn't change so there won't be ABI breakage and so such
feature can be safely implemented later.

There was also an idea of supporting other devices (PCI, SDIO, etc.) but
as this driver already contains some USB specific code (and will get
more) these should be probably separated drivers (triggers).

Signed-off-by: Rafał Miłecki <rafal@milecki.pl>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
 2016-09-27 12:20:17 +02:00