Return to enetBuffers CVS log

Up to [Apple Darwin 0.x] / driverkit / notes

Annotation of driverkit/notes/enetBuffers, revision 1.1

1.1     ! root        1:                      m88k ethernet buffer notes        
        !             2:                      
        !             3: 
        !             4: /*
        !             5:  * This is exactly 2k bytes, aligned to a 2k byte boundary. The actual
        !             6:  * DMA data is inside of here, aligned for proper enet DMA.
        !             7:  *
        !             8:  * An enetBuf as associated with a netbuf_t at getbuf time via the 
        !             9:  * freefunc and freefuncarg mechanism, and at RX DMA enqueue time by 
        !            10:  * setting dma_id = netbuf.
        !            11:  *
        !            12:  * We keep separate pools of TX and RX ebetBufs. For now, a fixed number 
        !            13:  * of TX and RX enetBufs are allocated at init time; no more are 
        !            14:  * allocated after that.
        !            15:  */
        !            16: typedef struct {
        !            17:        enetBuf_t *next;
        !            18:        id owner;
        !            19:        boolean_t Rx;
        !            20:        char filler[to align dmaData for DMA];
        !            21:        char dmaData[max packet size];
        !            22:        char filler[to fill out to 2048 bytes];
        !            23: } enetBuf_t;
        !            24: 
        !            25: boot {
        !            26:        create a list of empty enetBuf_t's, enqueue on RxBufList and 
        !            27:                TxBufList;
        !            28:        rxDmaQCount = 0;
        !            29:        do {
        !            30:                get an enetBuf from RxBufList;
        !            31:                netbuf = nb_alloc_wrapper(&enetBuf->dmaData,
        !            32:                        size of DMA Data,
        !            33:                        &enetBufFree(),
        !            34:                        &enetBuf);
        !            35:                /*
        !            36:                 * Our record of netbuf is via dma_id!
        !            37:                 */
        !            38:                dma_enqueue(data = &enetBuf.dmaData,
        !            39:                        dma_id = netbuf, 
        !            40:                        length = sizeof DMA data);
        !            41:                rxDmaQCount++;
        !            42:        } for each buf in RxBufList;
        !            43: }
        !            44:   
        !            45: getbuf {
        !            46:        get a free enetBuf from TxBufList;
        !            47:        return NULL if list empty;
        !            48:        return(nb_alloc_wrapper(&enetBuf->dmaData,
        !            49:                size of DMA Data,
        !            50:                &enetBufFree(),
        !            51:                &enetBuf));
        !            52: }
        !            53:   
        !            54: output {
        !            55:        dma_enqueue(data = nb_map(netbuf), 
        !            56:                dma_id = netbuf, 
        !            57:                length = nb_size(netbuf));
        !            58: }
        !            59: 
        !            60: TX DMA complete {
        !            61:        do {
        !            62:                dma_id = chan_dma_dequeue(COMPLETED);
        !            63:                nb_free((netbuf_t)dma_id);
        !            64:        } for all frames;
        !            65: }
        !            66: 
        !            67: RX DMA complete {
        !            68:        do {
        !            69:                dma_id = chan_dma_dequeue(COMPLETED);
        !            70:                if_handle_input(netif, (netbuf_t)dma_id, NULL);
        !            71:        } for all frames;
        !            72:        do {
        !            73:                get an enetBuf from RxBufList;
        !            74:                netbuf = nb_alloc_wrapper(&enetBuf->dmaData,
        !            75:                        size of DMA Data,
        !            76:                        &enetBufFree(),
        !            77:                        &enetBuf);
        !            78:                dma_enqueue(data = &enetBuf.dmaData,
        !            79:                        dma_id = netbuf, 
        !            80:                        length = sizeof DMA data);
        !            81:                rxDmaQCount++;
        !            82:        
        !            83:        } for each buf in RxBufList; 
        !            84: }
        !            85: 
        !            86: /*
        !            87:  * Called out from nb_free(), as freefunc(freefunc_arg).
        !            88:  */
        !            89: enetBufFree(enetBuf_t *enetBuf) {
        !            90:        enqueue this on TxBufList or RxBufList;
        !            91: }
        !            92: 
        !            93: Notes
        !            94: -----
        !            95: 
        !            96: * Memory throttle is via getbuf returning NULL. Joel has a limit of 10 RX and
        !            97:   10 TX buffers in the Token Ring driver. Current 68k enet driver has no 
        !            98:   limit. Brad and Joel say that it should not cause problems for the
        !            99:   driver to return NULL on getbuf()...Brad will help track down problems
        !           100:   in this area.
        !           101:   

This archive runs on limited infrastructure. Preserving old code on modern bandwidth. Automated agents are requested to crawl responsibly.