void *mem; dma_addr_t mem_dma; mem = dma_alloc_coherent(dev, 4096, &mem_dma, GFP_KERNEL); if (!mem) { printk(KERN_ERR "Failed to allocate memory\n"); return; } memset(mem, 0, 4096); dma_free_coherent(dev, 4096, mem, mem_dma); 如果有n个void *mem;需要根据mem动态申请dma,代码展示

可以使用一个循环来动态申请n个void *mem，并且为每个mem申请相应的dma内存。以下是示例代码：

void **mem_array;
dma_addr_t *dma_array;
int i;

mem_array = kmalloc(n * sizeof(void *), GFP_KERNEL);
if (!mem_array) {
    printk(KERN_ERR "Failed to allocate memory array\n");
    return;
}

dma_array = kmalloc(n * sizeof(dma_addr_t), GFP_KERNEL);
if (!dma_array) {
    printk(KERN_ERR "Failed to allocate DMA array\n");
    kfree(mem_array);
    return;
}

for (i = 0; i < n; i++) {
    mem_array[i] = dma_alloc_coherent(dev, 4096, &dma_array[i], GFP_KERNEL);
    if (!mem_array[i]) {
        printk(KERN_ERR "Failed to allocate memory %d\n", i);
        goto fail;
    }

    memset(mem_array[i], 0, 4096);
}

// Free all memory and DMA resources
for (i = 0; i < n; i++) {
    dma_free_coherent(dev, 4096, mem_array[i], dma_array[i]);
}

kfree(dma_array);
kfree(mem_array);

return;

fail:
for (i = 0; i < n; i++) {
    if (mem_array[i]) {
        dma_free_coherent(dev, 4096, mem_array[i], dma_array[i]);
    }
}

kfree(dma_array);
kfree(mem_array);

注意，如果在循环中出现了错误，需要跳转到fail标签处进行资源的释放，这样可以确保所有的资源都能够被正确地释放。