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I've been tasked with making a custom kernel module that reads the memory of a NIC device, from the family of Broadcom chipsets.

In my case I'm using a BCM4311, have installed the firmware and the kernel driver, but I can't seem to get a grasp on how to access the device object memory. I know the memory I/O char and block devices, etc. But NICs are quite complex...

Does the B43 handle the memory access for me? How can I access the physical memory from the device? Can't get a /dev/<nic>, do I have to use an ioctl? But ioctl does not equal to physical memory, right?

I am somewhat confused by this topic...

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  • If the driver does not enable in whatever way what you want then I am afraid (really) that /dev/mem together with detailed documentation of your device will be your two unique friends. Commented Nov 20, 2022 at 0:31
  • @MC68020 So, if i were to rea the physical mem of my device. I would have to read the /dev/mem starting at the corresponding address (in my case, using lspci returns a Region 0: Memory at 0x<Address>), am I right? Commented Nov 20, 2022 at 10:54
  • Basically yes. Being said you'll almost certainly need to mmap it. Since, playing with /dev/mem can just break your system (even when you think you know what you are doing), I strongly urge you to consider busybox' devmem utility ( github.com/brgl/busybox/blob/master/miscutils/devmem.c ) It might well in itself just fulfill all your needs or… at least… give you some useful hints. Commented Nov 20, 2022 at 12:15

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