rapidio: add RapidIO documentation

Add RapidIO documentation files as it was discussed earlier (see thread
http://marc.info/?l=linux-kernel&m=129202338918062&w=2)

Signed-off-by: Alexandre Bounine <alexandre.bounine@idt.com>
Cc: Kumar Gala <galak@kernel.crashing.org>
Cc: Matt Porter <mporter@kernel.crashing.org>
Cc: Randy Dunlap <rdunlap@xenotime.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 90 insertions, 0 deletions

diff --git a/Documentation/rapidio/sysfs.txt b/Documentation/rapidio/sysfs.txt
new file mode 100644
index 0000000..97f71ce
--- /dev/null
+++ b/Documentation/rapidio/sysfs.txt
@@ -0,0 +1,90 @@
+                         RapidIO sysfs Files
+
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+1. Device Subdirectories
+------------------------
+
+For each RapidIO device, the RapidIO subsystem creates files in an individual
+subdirectory with the following name, /sys/bus/rapidio/devices/<device_name>.
+
+The format of device_name is "nn:d:iiii", where:
+
+nn - two-digit hexadecimal ID of RapidIO network where the device resides
+d  - device typr: 'e' - for endpoint or 's' - for switch
+iiii - four-digit device destID for endpoints, or switchID for switches
+
+For example, below is a list of device directories that represents a typical
+RapidIO network with one switch, one host, and two agent endpoints, as it is
+seen by the enumerating host (destID = 1):
+
+/sys/bus/rapidio/devices/00:e:0000
+/sys/bus/rapidio/devices/00:e:0002
+/sys/bus/rapidio/devices/00:s:0001
+
+NOTE: An enumerating or discovering endpoint does not create a sysfs entry for
+itself, this is why an endpoint with destID=1 is not shown in the list.
+
+2. Attributes Common for All Devices
+------------------------------------
+
+Each device subdirectory contains the following informational read-only files:
+
+       did - returns the device identifier
+       vid - returns the device vendor identifier
+device_rev - returns the device revision level
+   asm_did - returns identifier for the assembly containing the device
+   asm_rev - returns revision level of the assembly containing the device
+   asm_vid - returns vendor identifier of the assembly containing the device
+   destid  - returns device destination ID assigned by the enumeration routine
+             (see 4.1 for switch specific details)
+   lprev   - returns name of previous device (switch) on the path to the device
+             that that owns this attribute
+
+In addition to the files listed above, each device has a binary attribute file
+that allows read/write access to the device configuration registers using
+the RapidIO maintenance transactions:
+
+ config - reads from and writes to the device configuration registers.
+
+This attribute is similar in behavior to the "config" attribute of PCI devices
+and provides an access to the RapidIO device registers using standard file read
+and write operations.
+
+3. Endpoint Device Attributes
+-----------------------------
+
+Currently Linux RapidIO subsystem does not create any endpoint specific sysfs
+attributes. It is possible that RapidIO master port drivers and endpoint device
+drivers will add their device-specific sysfs attributes but such attributes are
+outside the scope of this document.
+
+4. Switch Device Attributes
+---------------------------
+
+RapidIO switches have additional attributes in sysfs. RapidIO subsystem supports
+common and device-specific sysfs attributes for switches. Because switches are
+integrated into the RapidIO subsystem, it offers a method to create
+device-specific sysfs attributes by specifying a callback function that may be
+set by the switch initialization routine during enumeration or discovery process.
+
+4.1 Common Switch Attributes
+
+   routes - reports switch routing information in "destID port" format. This
+            attribute reports only valid routing table entries, one line for
+            each entry.
+   destid - device destination ID that defines a route to the switch
+ hopcount - number of hops on the path to the switch
+    lnext - returns names of devices linked to the switch except one of a device
+            linked to the ingress port (reported as "lprev"). This is an array
+            names with number of lines equal to number of ports in switch. If
+            a switch port has no attached device, returns "null" instead of
+            a device name.
+
+4.2 Device-specific Switch Attributes
+
+Device-specific switch attributes are listed for each RapidIO switch driver
+that exports additional attributes.
+
+IDT_GEN2:
+ errlog - reads contents of device error log until it is empty.