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id *p;
/* touch every page in the allocated memory */
for (p = dma_virt[i]; p < dma_virt[i] + (i + 1) * SZ_1M; p += PAGE_SIZE)
*(u32 *)p = 0;
_dev_info(cma_dev, "alloc virt: %p phys: %p\n", dma_virt[i], (void *)dma_phys[i]);
} else {
dev_err(cma_dev, "no mem in CMA area\n");
ret = -ENOMEM;
}
break;
}
}
return count;
}
static const struct file_operations cma_test_fops = {
.owner = THIS_MODULE,
.read = cma_test_read,
.write = cma_test_write,
};
static struct miscdevice cma_test_misc = {
.name = "cma_test",
.fops = &cma_test_fops,
};
static int __init cma_test_init(void)
{
int ret = 0;
ret = misc_register(&cma_test_misc);
if (unlikely(ret)) {
pr_err("failed to register cma test misc device!\n");
return ret;
}
cma_dev = cma_test_misc.this_device;
cma_dev->coherent_dma_mask = ~0;
_dev_info(cma_dev, "registered.\n");
return ret;
}
module_init(cma_test_init);
static void __exit cma_test_exit(void)
{
misc_deregister(&cma_test_misc);
}
module_exit(cma_test_exit);
MODULE_LICENSE("GPL");
MODULE_AUTHOR("Barry Song <21cnbao@gmail.com>");
MODULE_DESCRIPTION("kernel module to help the test of CMA");
MODULE_ALIAS("CMA test");
申请内存：
# echo 0 > /dev/cma_test
释放内存：
# cat /dev/cma_test
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