[英]communicating with a PCI device through /dev/mem
I'm need to communicate with a memory PCI device through /dev/mem
. 我需要通过
/dev/mem
与内存PCI设备进行通信。 Why? 为什么? There are many reasons, one of which is because my boss told me so.
原因有很多,其中之一是因为我的老板告诉过我。
I think I have my answer here . 我想我在这里有答案。 What I can't figure out however is the
MMIO_ADDR
in the answer. 我不知道的是答案中的
MMIO_ADDR
。 If I want to communicate with a specific memory region, would I use a value stored in a BAR
register as my MMIO_ADDR
? 如果我想与特定的内存区域通信,是否可以将
BAR
寄存器中存储的值用作MMIO_ADDR
? If no then how do I communicate with my PCI device? 如果没有,我该如何与我的PCI设备通信?
Your BAR will have been assigned an address by the BIOS/kernel. BIOS /内核将为您的BAR分配一个地址。 That address should have been written into the BAR address registers in the PCI configuration header by the time the system is up.
在系统启动时,该地址应该已经写入PCI配置标头中的BAR地址寄存器中。
For example, on a VM I have here, the e1000 device is as follows (from lspci -v
): 例如,在我拥有的VM上,e1000设备如下(来自
lspci -v
):
02:03.0 Ethernet controller: Intel Corporation 82545EM Gigabit Ethernet Controller (Copper) (rev 01)
Subsystem: VMware PRO/1000 MT Single Port Adapter
Physical Slot: 35
Flags: bus master, 66MHz, medium devsel, latency 0, IRQ 17
=> Memory at fd560000 (64-bit, non-prefetchable) [size=128K]
Memory at fdfd0000 (64-bit, non-prefetchable) [size=64K]
I/O ports at 2080 [size=64]
[virtual] Expansion ROM at fd520000 [disabled] [size=64K]
Capabilities: <access denied>
Kernel driver in use: e1000
You'll need to read that info (you can reach it in binary form via /proc/bus/pci/<Bus>/<DevFn>
or via /sys/bus/pci/devices/
) to find the MMIO address. 您需要阅读该信息(可以通过
/proc/bus/pci/<Bus>/<DevFn>
或通过/sys/bus/pci/devices/
以二进制形式获取该信息)以找到MMIO地址。
For example, dumping the binary of the PCI configuration space for the device above shows: 例如,转储上述设备的PCI配置空间的二进制文件显示:
od -tx1z -Ax /proc/bus/pci/02/03.0
000000 86 80 0f 10 17 01 30 02 01 00 00 02 10 00 00 00 >......0.........<
000010 04 00 56 fd 00 00 00 00 04 00 fd fd 00 00 00 00 >..V.............<
000020 81 20 00 00 00 00 00 00 00 00 00 00 ad 15 50 07 >. ............P.<
000030 00 00 00 00 dc 00 00 00 00 00 00 00 0b 01 ff 00 >................<
000040
The first BAR (bar region #0) is at offset 0x10, the second (bar region #2) is at offset 0x18. 第一个BAR(条形区域#0)的偏移量为0x10,第二个BAR形条形区域#2的偏移量为0x18。
See https://en.wikipedia.org/wiki/PCI_configuration_space for description of the layout and interpretation. 有关布局和解释的说明,请参见https://en.wikipedia.org/wiki/PCI_configuration_space 。
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