Messages in this thread | | | Date | Fri, 17 Jun 2011 10:41:25 +0100 | From | Russell King - ARM Linux <> | Subject | Re: [PATCH 00/10] Enhance /dev/mem to allow read/write of arbitrary physical addresses |
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On Fri, Jun 17, 2011 at 11:30:32AM +0200, Ingo Molnar wrote: > I'm aware of these current /dev/mem uses: > > - Xorg maps below 4G non-RAM addresses and the video BIOS > > - It used to have some debugging role but these days kexec and kgdb > has largely taken over that role - partly due to the 4G limit. > > - there's some really horrible out-of-tree drivers that do mmap()s > via /dev/mem, those should be fixed if they want to move beyond > 4G: their char device should be mmap()able. > > - all distro kernel's i'm aware of use CONFIG_STRICT_DEVMEM=y, which > restricts /dev/mem to non-RAM pages of physical memory. > [ With the sad inclusion of the first 1MB, which Xorg needs. ]
There's another use case for /dev/mem:
- debugging via devmem2 on embedded platforms, where you want to be able to boot a kernel, and then peek and poke at MMIO registers either to verify register values or test things out.
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