USB: cxacru: add Documentation file

The sysfs attributes for exposing cxacru statistics/status information with
possible values is now explained in Documentation/networking/cxacru.txt
including information on the writable adsl_state attribute's commands and a
sample of the kernel log format.

Signed-off-by: Simon Arlott <simon@fire.lp0.eu>
Cc: Duncan Sands <duncan.sands@math.u-psud.fr>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

2 files changed, 86 insertions, 0 deletions

diff --git a/Documentation/networking/00-INDEX b/Documentation/networking/00-INDEX
index e06b6e3c1db5..153d84d281e6 100644
--- a/Documentation/networking/00-INDEX
+++ b/Documentation/networking/00-INDEX
@@ -32,6 +32,8 @@ cops.txt
         - info on the COPS LocalTalk Linux driver
 cs89x0.txt
         - the Crystal LAN (CS8900/20-based) Ethernet ISA adapter driver
+cxacru.txt
+        - Conexant AccessRunner USB ADSL Modem
 de4x5.txt
         - the Digital EtherWORKS DE4?? and DE5?? PCI Ethernet driver
 decnet.txt
diff --git a/Documentation/networking/cxacru.txt b/Documentation/networking/cxacru.txt
new file mode 100644
index 000000000000..b074681a963e
--- /dev/null
+++ b/Documentation/networking/cxacru.txt
@@ -0,0 +1,84 @@
+Firmware is required for this device: http://accessrunner.sourceforge.net/
+
+While it is capable of managing/maintaining the ADSL connection without the
+module loaded, the device will sometimes stop responding after unloading the
+driver and it is necessary to unplug/remove power to the device to fix this.
+
+Detected devices will appear as ATM devices named "cxacru". In /sys/class/atm/
+these are directories named cxacruN where N is the device number. A symlink
+named device points to the USB interface device's directory which contains
+several sysfs attribute files for retrieving device statistics:
+
+* adsl_controller_version
+
+* adsl_headend
+* adsl_headend_environment
+        Information about the remote headend.
+
+* downstream_attenuation (dB)
+* downstream_bits_per_frame
+* downstream_rate (kbps)
+* downstream_snr_margin (dB)
+        Downstream stats.
+
+* upstream_attenuation (dB)
+* upstream_bits_per_frame
+* upstream_rate (kbps)
+* upstream_snr_margin (dB)
+* transmitter_power (dBm/Hz)
+        Upstream stats.
+
+* downstream_crc_errors
+* downstream_fec_errors
+* downstream_hec_errors
+* upstream_crc_errors
+* upstream_fec_errors
+* upstream_hec_errors
+        Error counts.
+
+* line_startable
+        Indicates that ADSL support on the device
+        is/can be enabled, see adsl_start.
+
+* line_status
+        "initialising"
+        "down"
+        "attempting to activate"
+        "training"
+        "channel analysis"
+        "exchange"
+        "waiting"
+        "up"
+
+        Changes between "down" and "attempting to activate"
+        if there is no signal.
+
+* link_status
+        "not connected"
+        "connected"
+        "lost"
+
+* mac_address
+
+* modulation
+        "ANSI T1.413"
+        "ITU-T G.992.1 (G.DMT)"
+        "ITU-T G.992.2 (G.LITE)"
+
+* startup_attempts
+        Count of total attempts to initialise ADSL.
+
+To enable/disable ADSL, the following can be written to the adsl_state file:
+        "start"
+        "stop
+        "restart" (stops, waits 1.5s, then starts)
+        "poll" (used to resume status polling if it was disabled due to failure)
+
+Changes in adsl/line state are reported via kernel log messages:
+        [4942145.150704] ATM dev 0: ADSL state: running
+        [4942243.663766] ATM dev 0: ADSL line: down
+        [4942249.665075] ATM dev 0: ADSL line: attempting to activate
+        [4942253.654954] ATM dev 0: ADSL line: training
+        [4942255.666387] ATM dev 0: ADSL line: channel analysis
+        [4942259.656262] ATM dev 0: ADSL line: exchange
+        [2635357.696901] ATM dev 0: ADSL line: up (8128 kb/s down | 832 kb/s up)