问题描述
我正在为Linux中的DMA设备编写设备驱动程序.在Linux设备驱动程序，第15章，它说:
I am writing a device driver for a DMA device in Linux. In Linux Device Drivers, Chapter 15, it says:
我这样呼叫 kmalloc :
physical_pointer0 = kmalloc(number_of_bytes, GFP_DMA);
并打印如下结果:
printk(KERN_INFO "pinmem:pinmen_write kmalloc succeeded. pointer is %p, buffer size is %d\n", physical_pointer0, (unsigned)number_of_bytes);
这就是我所看到的:
Sep 9 00:29:45 nfellman_lnx kernel: [ 112.161744] pinmem:pinmen_write kmalloc succeeded. pointer is ffff880000180000, buffer size is 320800
如果我使用的是GFP_DMA，如何获取不适合24位的 0xffff880000180000 的指针?
How can I be getting a pointer to 0xffff880000180000, which doesn't fit in 24 bits, if I used GFP_DMA?
这可能不是我的内存块的物理地址吗?如果没有(那意味着我完全误解了 kmalloc )，如何获取其物理地址?
Could it be that this is not the physical address of my block of memory? If not (which would mean I'm completely misunderstanding kmalloc), how can I get its physical address?
我正在OpenSuse 12中工作.
I am working in OpenSuse 12.
推荐答案
答案似乎是 kmalloc 实际上并不返回物理指针，而是线性指针，我必须使用 virt_to_phys 转换为物理.
The answer to this appears to be that kmalloc doesn't in fact return a physical pointer, but rather a linear pointer, that I must convert to physical with virt_to_phys.
感谢 Alex Brown 提供了答案此处.
这篇关于在Linux中将kmalloc与GFP_DMA一起使用时，为什么得到高地址?的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持！