/* ethwrite.c - ethwrite */

#include 

/*------------------------------------------------------------------------
 * ethwrite - enqueue a packet for transmission on TI AM335X Ethernet
 *------------------------------------------------------------------------
 */
int32   ethwrite (
                struct  dentry *devptr,
                char    *buf,
                int32   count
        )
{
        struct  ethcblk *ethptr;        /* Ether entry pointer  */
        struct  eth_a_csreg *csrptr;    /* Ethernet CSR pointer */
        struct  eth_a_tx_desc *tdescptr;/* Tx Desc. pointer     */
        struct  eth_a_tx_desc *prev;    /* Prev. Desc. pointer  */

        ethptr = ðertab[devptr->dvminor];

        /* Get the pointer to the Ethernet CSR */
        csrptr = (struct eth_a_csreg *)ethptr->csr;

        /* Wait for an empty slot in the queue */
        wait(ethptr->osem);

        /* Get the pointer to the next descriptor */
        tdescptr = (struct eth_a_tx_desc *)ethptr->txRing +
                                                        ethptr->txTail;

        /* Adjust count if greater than max. possible packet size */
        if(count > PACKLEN) {
                count = PACKLEN;
        }

        /* Initialize the descriptor */
        tdescptr->next = NULL;
        tdescptr->buflen = count;
        tdescptr->bufoff = 0;
        tdescptr->packlen = count;
        tdescptr->stat = (ETH_AM335X_TDS_SOP |  /* Start of packet      */
                          ETH_AM335X_TDS_EOP |  /* End of packet        */
                          ETH_AM335X_TDS_OWN |  /* Own flag set for DMA */
                          ETH_AM335X_TDS_DIR |  /* Directed packet      */
                          ETH_AM335X_TDS_P1);   /* Output port is port1 */

        /* Copy the packet into the Tx buffer */
        memcpy((char *)tdescptr->buffer, buf, count);

        /* TODO Figure out why we need this hack        */
        /* This ethernet device does not send packets smaller than 60   */
        /* bytes; So pad a small packet to make it 60 bytes long        */

        if(count < 60) {
                memset((char *)tdescptr->buffer+count, 0, 60-count);
                tdescptr->buflen = 60;
                tdescptr->packlen = 60;
        }

        /* Insert the descriptor into Tx queue */

        if(csrptr->stateram->tx_hdp[0] == 0) {
                /* Tx queue is empty, this desc. will be the first */
                csrptr->stateram->tx_hdp[0] = (uint32)tdescptr;
        }
        else {
                /* Tx queue not empty, insert at end */
                prev = (struct eth_a_tx_desc *)
                                csrptr->stateram->tx_hdp[0];
                while(prev->next != NULL) {
                        prev = prev->next;
                }
                prev->next = tdescptr;
        }

        /* Increment the tail index of the Tx ring */
        ethptr->txTail++;
        if(ethptr->txTail >= ethptr->txRingSize) {
                ethptr->txTail = 0;
        }

        return count;
}