The usb_debug driver was modified to implement serial break handling
by using a "magic" data packet comprised of the sequence:
0x00 0xff 0x01 0xfe 0x00 0xfe 0x01 0xff
When the tty layer requests a serial break the usb_debug driver sends
the magic packet. On the receiving side the magic packet is thrown
away or a sysrq is activated depending on what kernel .config options
have been set.
The generic serial driver was modified as well as the usb serial
headers to generically implement sysrq processing in the same way the
non usb uart based drivers implement the sysrq handling. This will
allow other usb serial devices to implement sysrq handling as desired.
The new usb serial functions are named similarly and implemented
similarly to the uart functions as follows:
usb_serial_handle_break <-> uart_handle_break
usb_serial_handle_sysrq_char <-> uart_handle_sysrq_char
Signed-off-by: Jason Wessel <jason.wessel@windriver.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
The usb_debug driver, when used as the console, will always fail to
insert the carriage return and new line sequence as well as randomly
drop console output. This is a result of only having the single
write_urb and that the tty layer will have a lock that prevents the
processing of the back to back urb requests.
The solution is to allow more than one urb to be outstanding and have
a slightly deeper transmit queue. The idea and some code is borrowed
from the ftdi_sio usb driver.
The generic usb serial driver was modified so as to allow the classic
method of 1 write urb, or a multi write urb scheme with N allowed
outstanding urbs where N is controlled by max_in_flight_urbs. When
max_in_flight_urbs in a "struct usb_serial_driver" is non zero the
multi write urb scheme will be used.
The size of 4000 was selected for the usb_debug driver so that the
driver lowers possibility of losing the queued console messages during
the kernel startup.
Signed-off-by: Jason Wessel <jason.wessel@windriver.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
USB serial likes to use port->tty back pointers for the real work it does and
to do so without any actual locking. Unfortunately when you consider hangup
events, hangup/parallel reopen or even worse hangup followed by parallel close
events the tty->port and port->tty pointers are not guaranteed to be the same
as port->tty is the active tty while tty->port is the port the tty may or
may not still be attached to.
So rework the entire API to pass the tty struct. For console cases we need
to pass both for now. This shows up multiple drivers that immediately crash
with USB console some of which have been fixed in the process.
Longer term we need a proper tty as console abstraction
Signed-off-by: Alan Cox <alan@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
USB debug port only supports 8 byte rx/tx packets. Although spec implies that
"if a packet larger than eight bytes is received from the remote computer, the
device must break the larger packet into eight-byte packets before sending the
data to the Debug Port", the real PLX NET20DC device does not handle it right -
data is corrupted on debug port end if serial interface sends >8 byte urbs.
Patch below fixes the issue by limiting tx urb to 8 byte.
Signed off by: Aleks Gorelov <dared1st@yahoo.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
The usb-serial core no longer checks these fields so remove them from
all of the individual drivers. They will be removed from the usb-serial
core in a patch later in the series.
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
