DMA 8字节对齐的描述符程序

好久没更新blog，今天做网卡驱动的时候需要这样一个DMA描述符程序，要求描述符数组8字节对齐，于是写了一个来玩，如下：

#include <string.h>

#define u32 unsigned int
#define u8 unsigned char

typedef struct bd {
    u32 fsize;
    u8  *pdata;
}bd_t;

#define DMA_TXBD_MAX 3
#define DMA_RXBD_MAX 16

struct txbd {
    bd_t bds[DMA_TXBD_MAX];
}
#ifdef WIN32
#pragma warning(disable:4103)
#pragma pack(8)
#else
__attribute__ ((aligned (8)))
#endif
;

struct rxbd{
    bd_t bds[DMA_RXBD_MAX];
}
#ifdef WIN32
#pragma warning(disable:4103)
#pragma pack(8)
#else
__attribute__ ((aligned (8)))
#endif
;

#define DMA_TXBUF_SZ 1536
#define DMA_RXBUF_SZ 1536

static txbd tbds;
static rxbd rbds;

static u8 dma_txbuf[DMA_TXBD_MAX][DMA_TXBUF_SZ];
static u8 dma_rxbuf[DMA_RXBD_MAX][DMA_RXBUF_SZ];

#define init_bd(bdx,bufs,max) do{\
    int x=0; \
    while(x<(max)) { \
    ((bd_t*)(&bdx))[x].fsize=0; \
    ((bd_t*)(&bdx))[x].pdata=(bufs)[x]; \
    x++; \
    } \
}while(0);

#define _dump    printf

#define is_align(addr,bytes) (!((u32)(addr)%(bytes)))
#define check_align(bdx,max,bytes) do { \
    int x=0; \
    while(x<(max)) { \
        if(!is_align(&((bdx).bds[x]),(bytes))) \
            _dump("%02d.align(%d) failed! ptr:0x%08X\r\n",(x),(bytes),&((bdx).bds[x])); \
        else \
            _dump("%02d.align(%d) passed! ptr:0x%08X\r\n",(x),(bytes),&((bdx).bds[x])); \
        x++; \
    } \
}while(0);

#define MSG_VALIDATE "hello world!"

int main(int argc, char* argv[])
{
    int i;
    init_bd(tbds,dma_txbuf,DMA_TXBD_MAX);
    init_bd(rbds,dma_rxbuf,DMA_RXBD_MAX);
    check_align(tbds, DMA_TXBD_MAX, 8);
    check_align(rbds, DMA_RXBD_MAX, 8);

    for(i=0; i<DMA_TXBD_MAX; i++)
    {
        memcpy(tbds.bds[i].pdata, MSG_VALIDATE, sizeof(MSG_VALIDATE));
        _dump("%d. %s\r\n", i, dma_txbuf[i]);
    }

    for(i=0; i<DMA_RXBD_MAX; i++)
    {
        memcpy(rbds.bds[i].pdata, MSG_VALIDATE, sizeof(MSG_VALIDATE));
        _dump("%d. %s\r\n", i, dma_rxbuf[i]);
    }

    return 0;
}

完成！