Question

我正在学习内核（linux-3.1）网络驱动程序，卡驱动程序是smc91cx，我手边有SMSC lan91c111的数据表，那么数据表是否与代码匹配？如果是这样，我对驱动程序代码有一些疑问：

static int smc_hard_start_xmit(struct sk_buff *skb, struct net_device *dev)    {
    struct smc_local *lp = netdev_priv(dev);
void __iomem *ioaddr = lp->base;
unsigned int numPages, poll_count, status;
unsigned long flags;



DBG(3, "%s: %s\n", dev->name, __func__);

BUG_ON(lp->pending_tx_skb != NULL);

/*
 * The MMU wants the number of pages to be the number of 256 bytes
 * 'pages', minus 1 (since a packet can't ever have 0 pages :))
 *
 * The 91C111 ignores the size bits, but earlier models don't.
 *
 * Pkt size for allocating is data length +6 (for additional status
 * words, length and ctl)
 *
 * If odd size then last byte is included in ctl word.
 */
numPages = ((skb->len & ~1) + (6 - 1)) >> 8;
if (unlikely(numPages > 7)) {
    printk("%s: Far too big packet error.\n", dev->name);
    dev->stats.tx_errors++;
    dev->stats.tx_dropped++;
    dev_kfree_skb(skb);
    return NETDEV_TX_OK;
}

smc_special_lock(&lp->lock, flags);

/* now, try to allocate the memory */
SMC_SET_MMU_CMD(lp, MC_ALLOC | numPages); // why?
//  SMC_SET_MMU_CMD(lp, MC_ALLOC); // also work well 

/*
 * Poll the chip for a short amount of time in case the
 * allocation succeeds quickly.
 */
poll_count = MEMORY_WAIT_TIME;
do {
    status = SMC_GET_INT(lp);
    if (status & IM_ALLOC_INT) {
        printk(KERN_INFO "SMC91X: status & IM_ALLOC_INT\n");
        SMC_ACK_INT(lp, IM_ALLOC_INT);
        status = SMC_GET_INT(lp);
        if (status & IM_ALLOC_INT)
            printk(KERN_INFO "SMC91X: SMC_ACK_INT done.\n");
        break;
    }
} while (--poll_count);

smc_special_unlock(&lp->lock, flags);

lp->pending_tx_skb = skb;
if (!poll_count) {
    /* oh well, wait until the chip finds memory later */
    netif_stop_queue(dev);
    DBG(2, "%s: TX memory allocation deferred.\n", dev->name);
    SMC_ENABLE_INT(lp, IM_ALLOC_INT);
} else {
    /*
     * Allocation succeeded: push packet to the chip's own memory
     * immediately.
     */
    smc_hardware_send_pkt((unsigned long)dev);
}

return NETDEV_TX_OK;
}

看到代码片段，我添加了一些测试代码，我对SMC_SET_MMU_CMD(lp, MC_ALLOC | numPages);感到困惑这个宏最后设置了smc91c111卡的mmu命令寄存器，它只允许3位操作码，但为什么要添加numPages？

下一行是： SMC_ACK_INT(lp, IM_ALLOC_INT); 这个宏终于设置了Bank2 - 中断状态寄存器，数据表没有显示ALLOC INT可写，所以任何提示？

Answer 1

smc91x.c驱动程序涵盖91c111和旧芯片。＆＃34; 91C111忽略了尺寸位，但早期的型号没有。＆＃34;因此，

SMC_SET_MMU_CMD(lp, MC_ALLOC | numPages); // why?

和

SMC_SET_MMU_CMD(lp, MC_ALLOC); // also work well

都适用于91c111。但是，91c90 / c92 / c94 / c95 / c100可能需要传入numPages。在91c111上，用于numPages的位标记为＆＃39;保留＆＃39;，但它可能是＆＃39; ;忽略＆＃39;是一个更接近的术语。

至于

SMC_ACK_INT(lp, IM_ALLOC_INT);

当您第一次使用这种数据表时，文档显示中断状态寄存器（ISR）的方式可能有点令人困惑。如果你看看＆＃39;偏移＆＃39;在数据表中的列中，您会注意到中断确认寄存器（IAR）也处于0xC，这意味着该地址是共享的，但基于读取或写入的行为有所不同。具体来说，因为IAR中的位与ISR中的位相同，所以这也称为Write-One-To-Clear-Register（使用＆＃34; W1C寄存器＆＃34;在谷歌中）。

如果ISR / IAR是一个读写寄存器，它会打开一个竞争条件，内核可能会读取ISR，清除一点，然后在将其存储回ISR之前，硬件会设置另一个位在ISR中，然后内核用现在陈旧的副本覆盖ISR。

困惑linux smc91cx驱动程序代码和相关的数据表？

1 个答案: