linux.git/drivers/usb/gadget/function/u_serial.c, branch v5.8

usb: gadget: u_serial: add suspend resume callbacks

2020-05-25T08:09:39+00:00

Add suspend resume callbacks to handle the case seen when the bus is
suspended by the HOST, and the device opens the port (cat /dev/ttyGS0).

Gadget controller (like DWC2) doesn't accept usb requests to be queued in
this case (when in L2 state), from the gs_open() call. Error log is printed
- configfs-gadget gadget: acm ttyGS0 can't notify serial state, -11
If the HOST resumes (opens) the bus, the port still isn't functional.

Use suspend/resume callbacks to monitor the gadget suspended state by using
'suspended' flag. In case the port gets opened (cat /dev/ttyGS0), the I/O
stream will be delayed until the bus gets resumed by the HOST.

Signed-off-by: Fabrice Gasnier 
Signed-off-by: Felipe Balbi

usb: gadget: serial: fix Tx stall after buffer overflow

2020-02-11T06:45:45+00:00

Symptom: application opens /dev/ttyGS0 and starts sending (writing) to
it while either USB cable is not connected, or nobody listens on the
other side of the cable. If driver circular buffer overflows before
connection is established, no data will be written to the USB layer
until/unless /dev/ttyGS0 is closed and re-opened again by the
application (the latter besides having no means of being notified about
the event of establishing of the connection.)

Fix: on open and/or connect, kick Tx to flush circular buffer data to
USB layer.

Signed-off-by: Sergey Organov 
Reviewed-by: Michał Mirosław 
Signed-off-by: Felipe Balbi

usb: gadget: u_serial: use mutex for serialising open()s

2019-10-22T07:27:20+00:00

Remove home-made waiting mechanism from gs_open() and rely on
portmaster's mutex to do the job.

Note: This releases thread waiting on close() when another thread
open()s simultaneously.

Signed-off-by: Michał Mirosław 
Signed-off-by: Felipe Balbi

usb: gadget: u_serial: diagnose missed console messages

2019-10-22T07:27:17+00:00

Insert markers in console stream marking places where data
is missing. This makes the hole in the data stand out clearly
instead of glueing together unrelated messages.

Example output as seen from USB host side:

[    0.064078] pinctrl core: registered pin 16 (UART3_RTS_N PC0) on 70000868.pinmux
[    0.064130] pinctrl
[missed 114987 bytes]
[    4.302299] udevd[134]: starting version 3.2.5
[    4.306845] random: udevd: uninitialized urandom read (16 bytes read)

Signed-off-by: Michał Mirosław 
Reviewed-by: Greg Kroah-Hartman 
Signed-off-by: Felipe Balbi

usb: gadget: u_serial: allow more console gadget ports

2019-10-22T07:27:12+00:00

Allow configuring more than one console using USB serial or ACM gadget.

By default, only first (ttyGS0) is a console, but this may be changed
using function's new "console" attribute.

Signed-off-by: Michał Mirosław 
Signed-off-by: Felipe Balbi

usb: gadget: u_serial: make OBEX port not a console

2019-10-22T07:27:09+00:00

Prevent OBEX serial port from ever becoming a console. Console messages
will definitely break the protocol, and since you have to instantiate
the port making it explicitly for OBEX, there is no point in allowing
console to break it by mistake.

Signed-off-by: Michał Mirosław 
Reviewed-by: Greg Kroah-Hartman 
Signed-off-by: Felipe Balbi

usb: gadget: u_serial: reimplement console support

2019-10-22T07:27:06+00:00

Rewrite console support to fix a few shortcomings of the old code
preventing its use with multiple ports. This removes some duplicated
code and replaces a custom kthread with simpler workqueue item.

Only port ttyGS0 gets to be a console for now.

Signed-off-by: Michał Mirosław 
Reviewed-by: Greg Kroah-Hartman 
Tested-by: Ladislav Michl 
Signed-off-by: Felipe Balbi

usb: gadget: u_serial: add missing port entry locking

2019-10-22T07:27:04+00:00

gserial_alloc_line() misses locking (for a release barrier) while
resetting port entry on TTY allocation failure. Fix this.

Cc: stable@vger.kernel.org
Signed-off-by: Michał Mirosław 
Reviewed-by: Greg Kroah-Hartman 
Tested-by: Ladislav Michl 
Signed-off-by: Felipe Balbi

usb: gadget: u_serial: process RX in workqueue instead of tasklet

2019-01-28T10:51:30+00:00

Switch RX processing from tasklet to (delayed) work queue. This allows
receiver more room to process incoming data and prevents flood of
"ttyGS0: RX not scheduled?" messages on HS receive on slow CPU.

A side effect is 2.4MB/s zmodem transfer speed (up from 1.8MB/s)
on my test board.

Signed-off-by: Michał Mirosław 
Signed-off-by: Felipe Balbi

usb: gadget: u_serial: Use kfifo instead of homemade circular buffer

2017-12-11T10:36:50+00:00

The kernel FIFO implementation, kfifo, provides interfaces to manipulate
a first-in-first-out circular buffer.  Use kfifo instead of the homemade
one to make the code more concise and readable.

Signed-off-by: Lu Baolu 
Signed-off-by: Felipe Balbi