✎ soc:2010:cooldavid:journal:week2

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=== Week 2: Discuss TCP and memory changes, update jme driver ===
== TCP / memory topic ==
  * Current heap size is fixed at 128K.
  * Although it only uses 128K, all-drivers image already overlapped with heap address.
  * Trying to figure out a way to obtain more memory, and report it to OS.
  * See if it is possiable to know how much heap size we can use out of code and stack.

== jme driver ==
  * From Joshua Oreman
    * jme_check_link(struct net_device *netdev, int testonly)\\
      * In this function, I believe the code and string data used in constructing linkmsg will make it into even non-debug versions of the executable. If that's true it would be better if you could perform all the manipulations in the final DBG() line, using the ?: operator and such. It's possible the compiler is clever enough to know what strcat() does and see that linkmsg[] is not used in non-debug, though, so this may be moot.
  * From Michael Brown
    * if (memcmp(addr, netdev->hw_addr, ETH_ALEN))
      * No need for this compare; just always write the MAC address.  (This code will fail if you set the MAC to a non-default value, then try to set it back.)
    * Code cleanups
      * gPXE dose not use any DMA address that is above 4G <code C>
#if __x86_64__
     rxdesc->desc1.flags     = RXFLAG_64BIT;
#endif
</code>
      * Use struct ethhdr and eth_ntoa().
      * Drivers should generally not try to parse the packets they transmit and receive.
      * This code will break if/when software VLAN support is added. <code C>
            DBG2("Received packet: "
                 "from %02x:%02x:%02x:%02x:%02x:%02x "
                 "to %02x:%02x:%02x:%02x:%02x:%02x "
                 "type %04x\n",
                 *(uint8_t *)(rxbi->data + 6),
                 *(uint8_t *)(rxbi->data + 7),
                 *(uint8_t *)(rxbi->data + 8),
                 *(uint8_t *)(rxbi->data + 9),
                 *(uint8_t *)(rxbi->data + 10),
                 *(uint8_t *)(rxbi->data + 11),
                 *(uint8_t *)(rxbi->data + 0),
                 *(uint8_t *)(rxbi->data + 1),
                 *(uint8_t *)(rxbi->data + 2),
                 *(uint8_t *)(rxbi->data + 3),
                 *(uint8_t *)(rxbi->data + 4),
                 *(uint8_t *)(rxbi->data + 5),
                 be16_to_cpu(*(uint16_t *)(rxbi->data + 12)));
</code>
      * %p should be used for printing out pointer values. <code C>
    DBG2("TX buffer address: %08lx(%08lx+%x)\n",
                    (unsigned long)iob->data, mapping, len);
</code>
    * This will behave poorly when memory runs out.  Better is to have a refill routine that runs after the poll(), and always attempts to refill up to a specified level. <code C>
    rxdesc += idx;
    if (jme_make_new_rx_buf(rxring->bufinf + idx)) {
            DBG("Dropped packet due to memory allocation error.\n");
            netdev_rx_err(netdev, NULL, -ENOMEM);
    } else {
</code>
Trace: • journal • under_construction • debian_lenny_iscsi • projpages • project_plan
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