[PATCH v1 1/3] ipmi: bt-i2c: added documentation for bt-i2c drivers

[Brendan Higgins]

Added device tree binding documentation for ipmi-bt-i2c (host) and
ipmi-bmc-bt-i2c (BMC) and documentation for the Block Transfer over I2C
(bt-i2c) protocol.

Signed-off-by: Brendan Higgins 
---
 Documentation/bt-i2c.txt   | 121 +
 .../devicetree/bindings/ipmi/ipmi-bt-i2c.txt   |  21 
 .../bindings/ipmi_bmc/ipmi-bmc-bt-i2c.txt  |  21 
 3 files changed, 163 insertions(+)
 create mode 100644 Documentation/bt-i2c.txt
 create mode 100644 Documentation/devicetree/bindings/ipmi/ipmi-bt-i2c.txt
 create mode 100644 
Documentation/devicetree/bindings/ipmi_bmc/ipmi-bmc-bt-i2c.txt

diff --git a/Documentation/bt-i2c.txt b/Documentation/bt-i2c.txt
new file mode 100644
index ..1b375359c519
--- /dev/null
+++ b/Documentation/bt-i2c.txt
@@ -0,0 +1,121 @@
+Linux Block Transfer over I2C (bt-i2c) interface description
+
+
+by Brendan Higgins  in 2016
+
+Introduction
+
+
+IPMI defines an interface for communication between a CPU, a BMC (Baseboard
+Management Controller), and sensors and various other peripherals. For a more
+complete description of IPMI please see:
+http://www.intel.com/content/www/us/en/servers/ipmi/ipmi-second-gen-interface-spec-v2-rev1-1.html
+
+IPMI defines a *common* message format, as in a set of fields that are common
+across all IPMI messages; they could be viewed as part of the framing
+information for an IPMI message. They include:
+
+   - netfn
+   - lun
+   - cmd
+
+netfn and cmd together define the type of the message; netfn can be viewed as a
+message class and cmd is a subtype of sorts. lun (logical unit number) is used
+for routing between messages between different interfaces. After the last field
+there is usually a variable length payload. Despite these common fields, the
+remainder of the framing varies widely between the IPMI defined hardware
+interfaces; some specify a length as part of the framing which is never more
+than a byte in length; others use a special signal to denote the end of 
message.
+Some IPMI hardware interfaces, the Block Transfer interface in particular,
+support a sequence number that aids in support of multiple in-flight IPMI
+messages.
+
+IPMI defines SSIF (SMBus System Interface) as the IPMI hardware interface for
+SMBus/I2C. It supports a maximum total message length of 255 bytes that is
+broken up across several SMBus block operations. It does not define a sequence
+field in the IPMI framing making it very difficult to support multiple in 
flight
+messages (it is also intentionally left out of the specification). SSIF also
+requires the slave device to NACK until it is ready to accept data (technically
+it only specifies that it may NACK until it is ready, but must NACK on 
attempted
+reads if it does not support SMBus Alert; however, this is an effective
+requirements since a slave device is supposed to start with SMBus Alert
+disabled); this again makes SSIF very difficult to support for some slave
+devices which may not support NACKing arbitrary messages; indeed, at the time 
of
+writing, the Linux I2C slave driver framework did not have support for sending
+NACKs.
+
+Block Transfer over I2C defines a new IPMI compatible interface that uses Block
+Transfer messages and semantics on top of plain old I2C; it does not assume 
that
+the I2C slave is capable of NACKing arbitrary messages; however, it is designed
+such that it could take advantage of SMBus Alert so that the master does not
+have to poll (the Linux I2C core slave mode does not currently support SMBus
+Alert, but a patch adding this support is currently on the way).
+
+Protocol Definition
+---
+
+Block Transfer over I2C uses the IPMI defined Block Transfer message format; it
+supports variable length messages with a maximum length of 255 bytes (limited 
by
+the IPMI Block Transfer length byte).
+
+A Block Transfer over I2C Request is structured as follows:
+
+--
+| I2C start | slave address / RW bit unset | Block Transfer message | ... 
(another message or stop ) |
+--
+
+Multiple requests can be sent before any responses are received. Sequence
+numbers are to be handled by the users of the drivers; thus, no semantics are
+prescribed to their usage; however, the slave driver is required to buffer at
+least 256 requests before dropping requests; this can be used in conjunction
+with sequence numbers to prevent messages from being dropped by the slave.
+
+A Block Transfer over I2C Response is structured as follows:
+
+
+| I2C start | slave address / RW bit set | Block Transfer 

[PATCH v1 1/3] ipmi: bt-i2c: added documentation for bt-i2c drivers

[Brendan Higgins]

Added device tree binding documentation for ipmi-bt-i2c (host) and
ipmi-bmc-bt-i2c (BMC) and documentation for the Block Transfer over I2C
(bt-i2c) protocol.

Signed-off-by: Brendan Higgins 
---
 Documentation/bt-i2c.txt   | 121 +
 .../devicetree/bindings/ipmi/ipmi-bt-i2c.txt   |  21 
 .../bindings/ipmi_bmc/ipmi-bmc-bt-i2c.txt  |  21 
 3 files changed, 163 insertions(+)
 create mode 100644 Documentation/bt-i2c.txt
 create mode 100644 Documentation/devicetree/bindings/ipmi/ipmi-bt-i2c.txt
 create mode 100644 
Documentation/devicetree/bindings/ipmi_bmc/ipmi-bmc-bt-i2c.txt

diff --git a/Documentation/bt-i2c.txt b/Documentation/bt-i2c.txt
new file mode 100644
index ..1b375359c519
--- /dev/null
+++ b/Documentation/bt-i2c.txt
@@ -0,0 +1,121 @@
+Linux Block Transfer over I2C (bt-i2c) interface description
+
+
+by Brendan Higgins  in 2016
+
+Introduction
+
+
+IPMI defines an interface for communication between a CPU, a BMC (Baseboard
+Management Controller), and sensors and various other peripherals. For a more
+complete description of IPMI please see:
+http://www.intel.com/content/www/us/en/servers/ipmi/ipmi-second-gen-interface-spec-v2-rev1-1.html
+
+IPMI defines a *common* message format, as in a set of fields that are common
+across all IPMI messages; they could be viewed as part of the framing
+information for an IPMI message. They include:
+
+   - netfn
+   - lun
+   - cmd
+
+netfn and cmd together define the type of the message; netfn can be viewed as a
+message class and cmd is a subtype of sorts. lun (logical unit number) is used
+for routing between messages between different interfaces. After the last field
+there is usually a variable length payload. Despite these common fields, the
+remainder of the framing varies widely between the IPMI defined hardware
+interfaces; some specify a length as part of the framing which is never more
+than a byte in length; others use a special signal to denote the end of 
message.
+Some IPMI hardware interfaces, the Block Transfer interface in particular,
+support a sequence number that aids in support of multiple in-flight IPMI
+messages.
+
+IPMI defines SSIF (SMBus System Interface) as the IPMI hardware interface for
+SMBus/I2C. It supports a maximum total message length of 255 bytes that is
+broken up across several SMBus block operations. It does not define a sequence
+field in the IPMI framing making it very difficult to support multiple in 
flight
+messages (it is also intentionally left out of the specification). SSIF also
+requires the slave device to NACK until it is ready to accept data (technically
+it only specifies that it may NACK until it is ready, but must NACK on 
attempted
+reads if it does not support SMBus Alert; however, this is an effective
+requirements since a slave device is supposed to start with SMBus Alert
+disabled); this again makes SSIF very difficult to support for some slave
+devices which may not support NACKing arbitrary messages; indeed, at the time 
of
+writing, the Linux I2C slave driver framework did not have support for sending
+NACKs.
+
+Block Transfer over I2C defines a new IPMI compatible interface that uses Block
+Transfer messages and semantics on top of plain old I2C; it does not assume 
that
+the I2C slave is capable of NACKing arbitrary messages; however, it is designed
+such that it could take advantage of SMBus Alert so that the master does not
+have to poll (the Linux I2C core slave mode does not currently support SMBus
+Alert, but a patch adding this support is currently on the way).
+
+Protocol Definition
+---
+
+Block Transfer over I2C uses the IPMI defined Block Transfer message format; it
+supports variable length messages with a maximum length of 255 bytes (limited 
by
+the IPMI Block Transfer length byte).
+
+A Block Transfer over I2C Request is structured as follows:
+
+--
+| I2C start | slave address / RW bit unset | Block Transfer message | ... 
(another message or stop ) |
+--
+
+Multiple requests can be sent before any responses are received. Sequence
+numbers are to be handled by the users of the drivers; thus, no semantics are
+prescribed to their usage; however, the slave driver is required to buffer at
+least 256 requests before dropping requests; this can be used in conjunction
+with sequence numbers to prevent messages from being dropped by the slave.
+
+A Block Transfer over I2C Response is structured as follows:
+
+
+| I2C start | slave address / RW bit set | Block Transfer message | ... 
(another message or stop ) |