axfer: fulfill manual section for libffado backend

I note that libffado backend has no support for suspend/resume because
libffado has enough implementation for these features even if it exports
some symbols for them. For this backend, reception of signals for the
features brings abortion of runtime.

Signed-off-by: Takashi Sakamoto <[email protected]>
Signed-off-by: Takashi Iwai <[email protected]>

axfer/axfer-transfer.1

@@ -245,7 +245,89 @@ Select backend of transmission from a list below. The default is libasound.
 
 .SS Backend options for libffado
 
-(placeholder)
+This backend is automatically available when configure script detects
+.I ffado_streaming_init()
+symbol in libffado shared object.
+
+.TP
+.B \-p, \-\-port
+
+This option uses given value to decide which 1394 OHCI controller is used to
+communicate. When Linux system has two 1394 OHCI controllers,
+.I 0
+or
+.I 1
+are available. Neither this option nor
+.I \-g
+is available at the same time. If nothing specified, libffado performs to
+communicate to units on IEEE 1394 bus managed by all of 1394 OHCI controller available in Linux system.
+
+.TP
+.B \-n, \-\-node
+
+This option uses given value to decide which unit is used to communicate. This
+option requires
+.I \-p
+option to indicate which 1394 OHCI controller is used to communicate to the
+specified unit.
+
+.TP
+.B \-g, \-\-guid
+
+This option uses given value to decide a target unit to communicate. The value
+should be prefixed with '0x' and consists of hexadecimal literal letters
+(0\-9, a\-f, A\-F). Neither this option nor
+.I \-p
+is available at the same time. If nothing specified, libffado performs to
+communicate to units on IEEE 1394 bus managed by all of 1394 OHCI controller
+available in Linux system.
+
+.TP
+.B \-\-frames\-per\-period
+
+This option uses given value to decide the number of audio data frame in one
+read/write operation. The operation is blocked till the number of available
+audio data frame exceeds the given value. As a default, 512 audio data frames
+is used.
+
+.TP
+.B \-\-periods\-per\-buffer
+
+This option uses given value to decide the size of intermediate buffer between
+this program and libffado. As a default, 2 periods per buffer is used.
+
+.TP
+.B \-\-slave
+
+This option allows this program to run slave mode. In this mode, libffado
+adds unit directory into configuration ROM of 1394 OHCI controller where Linux
+system runs. The unit directory can be found by the other node on the same bus.
+Linux system running on the node can transfer isochronous packet with audio
+data frame to the unit. This program can receive the packet and demultiplex the
+audio data frame.
+
+.TP
+.B \-\-snoop
+
+This option allows this program to run snoop mode. In this mode, libffado
+listens all isochronous channels. When isochronous communication starts
+by any unit on the same bus, the packets can be handled by this program.
+
+.TP
+.B \-\-sched\-priority
+
+This option executes
+.I pthread_setschedparam()
+in a call of
+.I ffado_streaming_init()
+to configure
+scheduling policy and given value as its priority for threads related to
+isochronous communication.
+The given value should be within
+.I RLIMIT_RTPRIO
+parameter of process. Please read
+.I getrlimit(2)
+for details.
 
 .SH POSIX SIGNALS
 During transmission,
@@ -257,7 +339,8 @@ will close handled files and PCM substream to be going to finish run time.
 .I SIGTSTP
 will suspend PCM substream and
 .I SIGCONT
-will resume it. No XRUNs are expected.
+will resume it. No XRUNs are expected. With libffado backend, the suspend/resume
+is not supported and runtime is aboeted immediately.
 
 The other signals perform default behaviours.