usb: serial: handle -EPROTO quietly in generic_read_bulk

If a USB serial device is unplugged while there is an active program
using the device it will spam the logs with -EPROTO (71) messages as it
attempts to retry.

Most serial usb drivers (metro-usb, pl2303, mos7840, ...) only output
these messages for debugging.  The generic driver treats these as
errors.

Change the default output for the generic serial driver from error to
debug.

Signed-off-by: Jeremiah Mahler <jmmahler@gmail.com>
usb: serial: handle -ENODEV quietly in generic_submit_read_urb

If a USB serial device (e.g. /dev/ttyUSB0) with an active program is
unplugged, an -ENODEV (19) error will be produced after it gives up
trying to resubmit a read.

  usb_serial_generic_submit_read_urb - usb_submit_urb failed: -19

Add -ENODEV as one of the permanent errors along with -EPERM that
usb_serial_generic_submit_read_urb() handles quietly without an error.

Signed-off-by: Jeremiah Mahler <jmmahler@gmail.com>
doc: usbmon: fix wording "be reading until"

The usbmon documentation uses "be reading until" which is an uncommon
and confusing wording.  Change it to "read until it" which is more clear.

Signed-off-by: Jeremiah Mahler <jmmahler@gmail.com>
doc: usbmon: fix spelling s/unpriviledged/unprivileged/

Signed-off-by: Jeremiah Mahler <jmmahler@gmail.com>
doc: dynamic-debug: fix various wording issues

Fix various wording issues such as: "a another", incorrect use of plurals,
and others.

Signed-off-by: Jeremiah Mahler <jmmahler@gmail.com>
doc: dynamic-debug: fix headings and add title

Fix the capitilazation of the headings.  Change sub-headings to use
'---' instead of '===' and fix their alignment.  Add a title.

Signed-off-by: Jeremiah Mahler <jmmahler@gmail.com>
doc: dynamic-debug: remove description of when not set

When CONFIG_DYNAMIC_DEBUG is not set it falls back to using DEBUG, if
that is set, as you would expect.  Explaining this does not add much
to the document, remove it.

Signed-off-by: Jeremiah Mahler <jmmahler@gmail.com>
doc: dynamic-debug: remove simple text utility examples

Several examples explain basic operations with common text utilities
(cat, grep) which should be familiar to anyone who has used the command
line.  Since these don't help explain dynamic debug, remove them.

Signed-off-by: Jeremiah Mahler <jmmahler@gmail.com>
doc: dynamic-debug: cleanup code examples

Cleanup the code examples by removing unnecessary prefixes
(nullarbor:~), placing on one line where possible, removing unnecessary
'-n' with echo, eliminating C99 comments, indenting with 2 spaces,
and removing the statements of "Example" before an example.

Signed-off-by: Jeremiah Mahler <jmmahler@gmail.com>
doc: dynamic-debug: format spec with spaces

The query spec uses a combination of spaces and tabs which will
cause it to look mis-formatted if the tab spacing is not set to 8.
Replace the tabs with spaces so it always looks right.

Signed-off-by: Jeremiah Mahler <jmmahler@gmail.com>
doc: dynamic-debug: re-write introduction

The introduction should give the reader a clear idea of what they
can do with the system and what its capabilities are.  Details
can be left for later in the document.  Re-write the introduction
to achieve this.

Signed-off-by: Jeremiah Mahler <jmmahler@gmail.com>