d269d4434c
The USB console currently allocates a temporary fake tty which is used to pass terminal settings to the underlying serial driver. The tty struct is not fully initialised, something which can lead to a lockdep warning (or worse) if a serial driver tries to acquire a line-discipline reference: usbserial: USB Serial support registered for pl2303 pl2303 1-2.1:1.0: pl2303 converter detected usb 1-2.1: pl2303 converter now attached to ttyUSB0 INFO: trying to register non-static key. the code is fine but needs lockdep annotation. turning off the locking correctness validator. CPU: 0 PID: 68 Comm: udevd Tainted: G W 3.18.0-rc5 #10 [<c0016f04>] (unwind_backtrace) from [<c0013978>] (show_stack+0x20/0x24) [<c0013978>] (show_stack) from [<c0449794>] (dump_stack+0x24/0x28) [<c0449794>] (dump_stack) from [<c006f730>] (__lock_acquire+0x1e50/0x2004) [<c006f730>] (__lock_acquire) from [<c0070128>] (lock_acquire+0xe4/0x18c) [<c0070128>] (lock_acquire) from [<c027c6f8>] (ldsem_down_read_trylock+0x78/0x90) [<c027c6f8>] (ldsem_down_read_trylock) from [<c027a1cc>] (tty_ldisc_ref+0x24/0x58) [<c027a1cc>] (tty_ldisc_ref) from [<c0340760>] (usb_serial_handle_dcd_change+0x48/0xe8) [<c0340760>] (usb_serial_handle_dcd_change) from [<bf000484>] (pl2303_read_int_callback+0x210/0x220 [pl2303]) [<bf000484>] (pl2303_read_int_callback [pl2303]) from [<c031624c>] (__usb_hcd_giveback_urb+0x80/0x140) [<c031624c>] (__usb_hcd_giveback_urb) from [<c0316fc0>] (usb_giveback_urb_bh+0x98/0xd4) [<c0316fc0>] (usb_giveback_urb_bh) from [<c0042e44>] (tasklet_hi_action+0x9c/0x108) [<c0042e44>] (tasklet_hi_action) from [<c0042380>] (__do_softirq+0x148/0x42c) [<c0042380>] (__do_softirq) from [<c00429cc>] (irq_exit+0xd8/0x114) [<c00429cc>] (irq_exit) from [<c007ae58>] (__handle_domain_irq+0x84/0xdc) [<c007ae58>] (__handle_domain_irq) from [<c000879c>] (omap_intc_handle_irq+0xd8/0xe0) [<c000879c>] (omap_intc_handle_irq) from [<c0014544>] (__irq_svc+0x44/0x7c) Exception stack(0xdf4e7f08 to 0xdf4e7f50) 7f00: debc0b80 df4e7f5c 00000000 00000000 debc0b80 be8da96c 7f20: 00000000 00000128 c000fc84 df4e6000 00000000 df4e7f94 00000004 df4e7f50 7f40: c038ebc0 c038d74c 600f0013 ffffffff [<c0014544>] (__irq_svc) from [<c038d74c>] (___sys_sendmsg.part.29+0x0/0x2e0) [<c038d74c>] (___sys_sendmsg.part.29) from [<c038ec08>] (SyS_sendmsg+0x18/0x1c) [<c038ec08>] (SyS_sendmsg) from [<c000fa00>] (ret_fast_syscall+0x0/0x48) console [ttyUSB0] enabled Fixes: 36697529b5bb ("tty: Replace ldisc locking with ldisc_sem") Cc: stable <stable@vger.kernel.org> Signed-off-by: Johan Hovold <johan@kernel.org>
To understand all the Linux-USB framework, you'll use these resources:
* This source code. This is necessarily an evolving work, and
includes kerneldoc that should help you get a current overview.
("make pdfdocs", and then look at "usb.pdf" for host side and
"gadget.pdf" for peripheral side.) Also, Documentation/usb has
more information.
* The USB 2.0 specification (from www.usb.org), with supplements
such as those for USB OTG and the various device classes.
The USB specification has a good overview chapter, and USB
peripherals conform to the widely known "Chapter 9".
* Chip specifications for USB controllers. Examples include
host controllers (on PCs, servers, and more); peripheral
controllers (in devices with Linux firmware, like printers or
cell phones); and hard-wired peripherals like Ethernet adapters.
* Specifications for other protocols implemented by USB peripheral
functions. Some are vendor-specific; others are vendor-neutral
but just standardized outside of the www.usb.org team.
Here is a list of what each subdirectory here is, and what is contained in
them.
core/ - This is for the core USB host code, including the
usbfs files and the hub class driver ("hub_wq").
host/ - This is for USB host controller drivers. This
includes UHCI, OHCI, EHCI, and others that might
be used with more specialized "embedded" systems.
gadget/ - This is for USB peripheral controller drivers and
the various gadget drivers which talk to them.
Individual USB driver directories. A new driver should be added to the
first subdirectory in the list below that it fits into.
image/ - This is for still image drivers, like scanners or
digital cameras.
../input/ - This is for any driver that uses the input subsystem,
like keyboard, mice, touchscreens, tablets, etc.
../media/ - This is for multimedia drivers, like video cameras,
radios, and any other drivers that talk to the v4l
subsystem.
../net/ - This is for network drivers.
serial/ - This is for USB to serial drivers.
storage/ - This is for USB mass-storage drivers.
class/ - This is for all USB device drivers that do not fit
into any of the above categories, and work for a range
of USB Class specified devices.
misc/ - This is for all USB device drivers that do not fit
into any of the above categories.