Hi Ran On Wed, Sep 16, 2015 at 1:10 AM, Ran Shalit <ranshalit@gmail.com> wrote:

Hello,

I need to implement mmap for non-volatile memory chip (NVRAM). I already did something simple, but now I understand that it is not complete: The nvram need to be unlock and locked after finishing the memory task of read/write.

I guess you are better off with an ioctl call to the driver and be done with the read/write. You won't get faults once you've mapped it. So I don't think you can do locking via your driver after that. If you are thinking of doing something like below P1--->mmap--->driver [OK] P2-->mmap--->driver[OK] You won't be able to get the faults for the below cases as you would've already filled the vma for that in your vm_fault handler. P1--->writes to mmaped [No fault] P2--->writes to mmaped [No fault] You can't lock once both have mapped. What you can do is provide a different mapping[?] and then sync that mapping I guess? But that's just insane. If you say that subsequent mmap would fail then again you'll have to code user-space to work with this. Better off with ioctl rather than mmap.

Does mmap can handle such post/pre actions or not ( I guess that if not - I will need to use read/write alternatives) ?

Thank you, Ran

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