gldm_send() Entry Point

int prefix_send(gld_mac_info_t * macinfo, mblk_t * mp);

gldm_send() queues a packet to the device for transmission. This routine is passed a STREAMS message containing the packet to be sent. The message might include multiple message blocks, and the send routine must traverse all the message blocks in the message to access the entire packet to be sent. The driver should be prepared to handle and skip over any zero-length message continuation blocks in the chain. The driver should check that the packet does not exceed the maximum allowable packet size, and it must pad the packet, if necessary, to the minimum allowable packet size. If the send routine successfully transmits or queues the packet, it should return GLD_SUCCESS.

The send routine should return GLD_NORESOURCES if it cannot immediately accept the packet for transmission; in this case GLD will retry it later. If gldm_send() ever returns GLD_NORESOURCES, the driver must, at a later time when resources have become available, call gld_sched(). This call to gld_sched() informs GLD that it should retry packets that the driver previously failed to queue for transmission. (If the driver's gldm_stop() routine is called, the driver is absolved from this obligation until it later again returns GLD_NORESOURCES from its gldm_send() routine. However, extra calls to gld_sched() will not cause incorrect operation.)

If the driver's send routine returns GLD_SUCCESS, then the driver is responsible for freeing the message when the driver and the hardware no longer need it. If the send routine copied the message into the device, or into a private buffer, then the send routine is permitted to free the message after the copy is made. If the hardware uses DMA to read the data directly out of the message data blocks, then the driver must not free the message until the hardware has completed reading the data. In this case the driver will probably free the message in the interrupt routine, or in a buffer reclaim operation at the beginning of a future send operation. If the send routine returns anything other than GLD_SUCCESS, then the driver must not free the message. Return GLD_NOLINK if gldm_send() is called when there is no physical connection to the network or link partner.