The hme driver is a "style 2" Data Link Service provider. All M_PROTO and M_PCPROTO type messages are interpreted as DLPI primitives. Valid DLPI primitives are defined in <sys/dlpi.h>. Refer to dlpi(7P) for more information. An explicit DL_ATTACH_REQ message by the user is required to associate the opened stream with a particular device (ppa). The ppa ID is interpreted as an unsigned long data type and indicates the corresponding device instance (unit) number. An error (DL_ERROR_ACK) is returned by the driver if the ppa field value does not correspond to a valid device instance number for this system. The device is initialized on first attach and de-initialized (stopped) at last detach.

The values returned by the driver in the DL_INFO_ACK primitive in response to the DL_INFO_REQ from the user are as follows:

• The maximum SDU is 1500 (ETHERMTU - defined in <sys/ethernet.h> ).
• The minimum SDU is 0.
• The dlsap address length is 8.
• The MAC type is DL_ETHER.
• The sap length values is -2 meaning the physical address component is followed immediately by a 2 byte sap component within the DLSAP address.
• The service mode is DL_CLDLS.
• No optional quality of service (QOS) support is included at present so the QOS fields are 0.
• The provider style is DL_STYLE2.
• The version is DL_VERSION_2.
• The broadcast address value is Ethernet/IEEE broadcast address (0xFFFFFF).

Once in the DL_ATTACHED state, the user must send a DL_BIND_REQ to associate a particular SAP (Service Access Pointer) with the stream. The hme driver interprets the sap field within the DL_BIND_REQ as an Ethernet "type" therefore valid values for the sap field are in the [0-0xFFFF] range. Only one Ethernet type can be bound to the stream at any time.

If the user selects a sap with a value of 0, the receiver will be in "802.3 mode". All frames received from the media having a "type" field in the range [0-1500] are assumed to be 802.3 frames and are routed up all open Streams which are bound to sap value 0. If more than one Stream is in "802.3 mode" then the frame will be duplicated and routed up multiple Streams as DL_UNITDATA_IND messages.

In transmission, the driver checks the sap field of the DL_BIND_REQ if the sap value is 0, and if the destination type field is in the range [0-1500]. If either is true, the driver computes the length of the message, not including initial M_PROTO mblk (message block), of all subsequent DL_UNITDATA_REQ messages and transmits 802.3 frames that have this value in the MAC frame header length field.

The hme driver DLSAP address format consists of the 6 byte physical (Ethernet) address component followed immediately by the 2 byte sap (type) component producing an 8 byte DLSAP address. Applications should not hardcode to this particular implementation-specific DLSAP address format but use information returned in the DL_INFO_ACK primitive to compose and decompose DLSAP addresses. The sap length, full DLSAP length, and sap/physical ordering are included within the DL_INFO_ACK. The physical address length can be computed by subtracting the sap length from the full DLSAP address length or by issuing the DL_PHYS_ADDR_REQ to obtain the current physical address associated with the stream.

Once in the DL_BOUND state, the user may transmit frames on the Ethernet by sending DL_UNITDATA_REQ messages to the hme driver. The hme driver will route received Ethernet frames up all those open and bound streams having a sap which matches the Ethernet type as DL_UNITDATA_IND messages. Received Ethernet frames are duplicated and routed up multiple open streams if necessary. The DLSAP address contained within the DL_UNITDATA_REQ and DL_UNITDATA_IND messages consists of both the sap (type) and physical (Ethernet) components.

In addition to the mandatory connectionless DLPI message set the driver additionally supports the following primitives.

The DL_ENABMULTI_REQ and DL_DISABMULTI_REQ primitives enable/disable reception of individual multicast group addresses. A set of multicast addresses may be iteratively created and modified on a per-stream basis using these primitives. These primitives are accepted by the driver in any state following DL_ATTACHED.

The DL_PROMISCON_REQ and DL_PROMISCOFF_REQ primitives with the DL_PROMISC_PHYS flag set in the dl_level field enables/disables reception of all ("promiscuous mode") frames on the media including frames generated by the local host. When used with the DL_PROMISC_SAP flag set this enables/disables reception of all sap (Ethernet type) values. When used with the DL_PROMISC_MULTI flag set this enables/disables reception of all multicast group addresses. The effect of each is always on a per-stream basis and independent of the other sap and physical level configurations on this stream or other streams.

The DL_PHYS_ADDR_REQ primitive returns the 6 octet Ethernet address currently associated (attached) to the stream in the DL_PHYS_ADDR_ACK primitive. This primitive is valid only in states following a successful DL_ATTACH_REQ.

The DL_SET_PHYS_ADDR_REQ primitive changes the 6 octet Ethernet address currently associated (attached) to this stream. The credentials of the process which originally opened this stream must be superuser. Otherwise EPERM is returned in the DL_ERROR_ACK. This primitive is destructive in that it affects all other current and future streams attached to this device. An M_ERROR is sent up all other streams attached to this device when this primitive is successful on this stream. Once changed, all streams subsequently opened and attached to this device will obtain this new physical address. Once changed, the physical address will remain until this primitive is used to change the physical address again or the system is rebooted, whichever comes first.

By default, the hme driver performs "auto-negotiation" to select the mode and speed of the link, when the Internal Transceiver is used.

When an External Transceiver is connected to the MII interface, the driver selects the External Transceiver for networking operations. If the External Transceiver supports "auto-negotiation", the driver uses the auto-negotiation procedure to select the link speed and mode. If the External Transceiver does not support auto-negotiation, it will select the highest priority mode supported by the transceiver.

• 100 Mbps, full-duplex
• 100 Mbps, half-duplex
• 10 Mbps, full-duplex
• 10 Mbps, half-duplex

The link can be in one of the 4 following modes:

These speeds and modes are described in the 100Base-TX standard.

The auto-negotiation protocol automatically selects:

• Operation mode (half-duplex or full-duplex)
• Speed (100 Mbps or 10 Mbps)

The auto-negotiation protocol does the following:

• Gets all the modes of operation supported by the Link Partner
• Advertises its capabilities to the Link Partner
• Selects the highest common denominator mode of operation based on the priorities

The internal transceiver is capable of all of the operating speeds and modes listed above. When the internal transceiver is used, by default, auto-negotiation is used to select the speed and the mode of the link and the common mode of operation with the Link Partner.

When an external transceiver is connected to the MII interface, the driver selects the external transceiver for networking operations. If the external transceiver supports auto-negotiation:

• The driver uses the auto-negotiation procedure to select the link speed and mode.

If the external transceiver does not support auto-negotiation

• The driver selects the highest priority mode supported by the transceiver.

Sometimes, the user may want to select the speed and mode of the link. The SUNW,hme device supports programmable "IPG" (Inter-Packet Gap) parameters ipg1 and ipg2. By default, the driver sets ipg1 to 8 byte-times and ipg2 to 4 byte-times (which are the standard values). Sometimes, the user may want to alter these values depending on whether the driver supports 10 Mbps or 100 Mpbs and accordingly, IPG will be set to 9.6 or 0.96 microseconds.

The hme driver provides for setting and getting various parameters for the SUNW,hme device. The parameter list includes:

current transceiver status

current link status

inter-packet gap

local transceiver capabilities

link partner capabilities

The local transceiver has two set of capabilities: one set reflects the capabilities of the hardware, which are read-only (RO) parameters and the second set reflects the values chosen by the user and is used in speed selection. There are read/write (RW) capabilities. At boot time, these two sets of capabilities will be the same. The Link Partner capabilities are also read only parameters because the current default value of these parameters can only be read and cannot be modified.