Driver documentation for yealink usb-p1k phones
  
  0. Status
  ~~~~~~~~~
  The p1k is a relatively cheap usb 1.1 phone with:
    - keyboard		full support, yealink.ko / input event API
    - LCD			full support, yealink.ko / sysfs API
    - LED			full support, yealink.ko / sysfs API
    - dialtone		full support, yealink.ko / sysfs API
    - ringtone		full support, yealink.ko / sysfs API
    - audio playback   	full support, snd_usb_audio.ko / alsa API
    - audio record     	full support, snd_usb_audio.ko / alsa API
  
  For vendor documentation see http://www.yealink.com
  
  
  1. Compilation (stand alone version)
  ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
  Currently only kernel 2.6.x.y versions are supported.
  In order to build the yealink.ko module do
  
    make
  
  If you encounter problems please check if in the MAKE_OPTS variable in
  the Makefile is pointing to the location where your kernel sources
  are located, default /usr/src/linux.
  
  
  1.1 Troubleshooting
  ~~~~~~~~~~~~~~~~~~~
  Q: Module yealink compiled and installed without any problem but phone
     is not initialized and does not react to any actions.
  A: If you see something like:
     hiddev0: USB HID v1.00 Device [Yealink Network Technology Ltd. VOIP USB Phone
     in dmesg, it means that the hid driver has grabbed the device first. Try to
     load module yealink before any other usb hid driver. Please see the
     instructions provided by your distribution on module configuration.
  
  Q: Phone is working now (displays version and accepts keypad input) but I can't
     find the sysfs files.
  A: The sysfs files are located on the particular usb endpoint. On most
     distributions you can do: "find /sys/ -name get_icons" for a hint.
  
  
  2. keyboard features
  ~~~~~~~~~~~~~~~~~~~~
  The current mapping in the kernel is provided by the map_p1k_to_key
  function:
  
     Physical USB-P1K button layout	input events
  
  
                up			     up
          IN           OUT		left,	right
               down			    down
  
        pickup   C    hangup		enter, backspace, escape
          1      2      3			1, 2, 3
          4      5      6			4, 5, 6,
          7      8      9			7, 8, 9,
          *      0      #			*, 0, #,
  
    The "up" and "down" keys, are symbolised by arrows on the button.
    The "pickup" and "hangup" keys are symbolised by a green and red phone
    on the button.
  
  
  3. LCD features
  ~~~~~~~~~~~~~~~
  The LCD is divided and organised as a 3 line display:
  
      |[]   [][]   [][]   [][]   in   |[][]
      |[] M [][] D [][] : [][]   out  |[][]
                                store
  
      NEW REP         SU MO TU WE TH FR SA
  
      [] [] [] [] [] [] [] [] [] [] [] []
      [] [] [] [] [] [] [] [] [] [] [] []
  
  
  Line 1	Format (see below)	: 18.e8.M8.88...188
  	Icon names		:   M  D  :  IN OUT STORE
  Line 2  Format			: .........
  	Icon name		: NEW REP SU MO TU WE TH FR SA
  Line 3  Format			: 888888888888
  
  
  Format description:
    From a userspace perspective the world is separated into "digits" and "icons".
    A digit can have a character set, an icon can only be ON or OFF.
  
    Format specifier
      '8' :  Generic 7 segment digit with individual addressable segments
  
      Reduced capability 7 segm digit, when segments are hard wired together.
      '1' : 2 segments digit only able to produce a 1.
      'e' : Most significant day of the month digit,
            able to produce at least 1 2 3.
      'M' : Most significant minute digit,
            able to produce at least 0 1 2 3 4 5.
  
      Icons or pictograms:
      '.' : For example like AM, PM, SU, a 'dot' .. or other single segment
  	  elements.
  
  
  4. Driver usage
  ~~~~~~~~~~~~~~~
  For userland the following interfaces are available using the sysfs interface:
    /sys/.../
             line1	Read/Write, lcd line1
             line2	Read/Write, lcd line2
             line3	Read/Write, lcd line3
  
  	   get_icons    Read, returns a set of available icons.
  	   hide_icon    Write, hide the element by writing the icon name.
  	   show_icon    Write, display the element by writing the icon name.
  
  	   map_seg7	Read/Write, the 7 segments char set, common for all
  	   		yealink phones. (see map_to_7segment.h)
  
  	   ringtone	Write, upload binary representation of a ringtone,
  	   		see yealink.c. status EXPERIMENTAL due to potential
  			races between async. and sync usb calls.
  
  
  4.1 lineX
  ~~~~~~~~~
  Reading /sys/../lineX will return the format string with its current value:
  
    Example:
    cat ./line3
    888888888888
    Linux Rocks!
  
  Writing to /sys/../lineX will set the corresponding LCD line.
   - Excess characters are ignored.
   - If less characters are written than allowed, the remaining digits are
     unchanged.
   - The tab '\t'and '
  ' char does not overwrite the original content.
   - Writing a space to an icon will always hide its content.
  
    Example:
    date +"%m.%e.%k:%M"  | sed 's/^0/ /' > ./line1
  
    Will update the LCD with the current date & time.
  
  
  4.2 get_icons
  ~~~~~~~~~~~~~
  Reading will return all available icon names and its current settings:
  
    cat ./get_icons
    on M
    on D
    on :
       IN
       OUT
       STORE
       NEW
       REP
       SU
       MO
       TU
       WE
       TH
       FR
       SA
       LED
       DIALTONE
       RINGTONE
  
  
  4.3 show/hide icons
  ~~~~~~~~~~~~~~~~~~~
  Writing to these files will update the state of the icon.
  Only one icon at a time can be updated.
  
  If an icon is also on a ./lineX the corresponding value is
  updated with the first letter of the icon.
  
    Example - light up the store icon:
    echo -n "STORE" > ./show_icon
  
    cat ./line1
    18.e8.M8.88...188
                 S
  
    Example - sound the ringtone for 10 seconds:
    echo -n RINGTONE > /sys/..../show_icon
    sleep 10
    echo -n RINGTONE > /sys/..../hide_icon
  
  
  5. Sound features
  ~~~~~~~~~~~~~~~~~
  Sound is supported by the ALSA driver: snd_usb_audio
  
  One 16-bit channel with sample and playback rates of 8000 Hz is the practical
  limit of the device.
  
    Example - recording test:
    arecord -v -d 10 -r 8000 -f S16_LE -t wav  foobar.wav
  
    Example - playback test:
    aplay foobar.wav
  
  
  6. Credits & Acknowledgments
  ~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    - Olivier Vandorpe, for starting the usbb2k-api project doing much of
  	the reverse engineering.
    - Martin Diehl, for pointing out how to handle USB memory allocation.
    - Dmitry Torokhov, for the numerous code reviews and suggestions.