From: pranjas@gmail.com (Pranay Srivastava)
To: kernelnewbies@lists.kernelnewbies.org
Subject: mmap - post/pre actions
Date: Wed, 16 Sep 2015 14:32:35 +0530 [thread overview]
Message-ID: <CA+aCy1EvBhRsREvMtHvASb+EDGx6R7kd+G5sn0cA2SUZoRLSfg@mail.gmail.com> (raw)
In-Reply-To: <CAJ2oMhL_uDPQLMztxCLMOX7YsvhxqKEPqKbpfROovzxHo24gsg@mail.gmail.com>
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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--
---P.K.S
prev parent reply other threads:[~2015-09-16 9:02 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-09-15 19:40 mmap - post/pre actions Ran Shalit
2015-09-15 19:51 ` Valdis.Kletnieks at vt.edu
2015-09-16 9:02 ` Pranay Srivastava [this message]
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