docs: vendor-ibm-astlpc: Add definitions for KCS registers
These were explained in the document body but deserve their own
definitions given their importance to the protocol.
Signed-off-by: Andrew Jeffery <andrew@aj.id.au>
Change-Id: I2cdf60dda74efba95e6e78bd4a53aa9558308d75
diff --git a/docs/bindings/vendor-ibm-astlpc.md b/docs/bindings/vendor-ibm-astlpc.md
index 98634c8..b311799 100644
--- a/docs/bindings/vendor-ibm-astlpc.md
+++ b/docs/bindings/vendor-ibm-astlpc.md
@@ -28,6 +28,17 @@
Defined by the MCTP base specification as the smallest maximum packet size all
MCTP-compliant endpoints must accept.
+**IBF: Input Buffer Full**
+
+A hardware-defined flag bit in a KCS device's Status Register (STR). The IBF
+flag indicates that a value has been written by the host to the corresponding
+Input Data Register (IDR).
+
+**IDR: Input Data Register**
+
+One of the three register interfaces exposed by a KCS device. The IDR is a one
+byte buffer which is written by the host and read by the BMC.
+
**KCS: Keyboard-Controller-Style**
A set of bit definitions and operation of the registers typically used in
@@ -57,6 +68,25 @@
MTU values larger than the BTU may improve throughput for data-intensive
transfers.
+**OBF: Output Buffer Full**
+
+A hardware-defined flag bit in a KCS device's Status Register (STR). The OBF
+flag indicates that a value has been written by the BMC to the corresponding
+Output Data Register (ODR).
+
+**ODR: Output Data Register**
+
+One of the three register interfaces exposed by a KCS device. The ODR is a
+one byte buffer which is written by the BMC and read by the host.
+
+**STR: Status Register**
+
+One of the three register interfaces exposed by a KCS device. STR is a
+BMC-controlled, eight-bit register exposed to both the BMC and the host for
+indication of IBF and OBF events on the input (IDR) and output (ODR) buffers.
+Bits that are not defined by hardware can be software-controlled in a manner
+defined by a platform-specific ABI.
+
## Conventions
Where unspecified, state, command and sequence descriptions apply to all
@@ -106,8 +136,8 @@
(ODR) and the Input Data Register (IDR). The ODR is written by the BMC and read
by the host. The IDR is the obverse.
-The KCS unit also contains a status register, allowing both host and BMC to
-determine if there is data in the ODR or IDR. These are single-bit flags,
+The KCS unit also contains a status register (STR), allowing both host and BMC
+to determine if there is data in the ODR or IDR. These are single-bit flags,
designated Input/Output Buffer Full (IBF/OBF), and are automatically set by
hardware when data has been written to the corresponding ODR/IDR buffer (and
cleared when data has been read).