On Mon, Sep 14, 2009 at 2:19 PM, Leonidas . <leonidas137@xxxxxxxxx> wrote:
No, Greg KH mentions that is should not be done!On Mon, Sep 14, 2009 at 1:57 PM, Pei Lin <telent997@xxxxxxxxx> wrote:
SO u can use the first method,write files from the kernel space.....
See the hyperlink i give.
> On Mon, Sep 14, 2009 at 1:22 PM, Leonidas . <leonidas137@xxxxxxxxx> wrote:
>>
>>
>> Hi List
>>
>> I have written a kernel module which implements a char device. An
>> userspace app
>> is supposed to get data from my module and then dump it into a file for
>> further processing.
>>
>> The kind of data which kernel module is going to pass to userspace is
>> going to be a 4K buffer,
>> and the data traffic is not going to be really heavy, meaning may be a 4K
>> buffer every 1 min or so.
>> I am not very sure though, but certainly not heavy traffic the way they
>> describe for network traffic etc.
>>
>> And this data needs to be logged to a file either from kernel or userspace
>> and an userspace all will work
>> on that data. This data needs to be logged as soon as it arrives meaning,
>> I might not be able to write it to
>> /proc since from module I can update /proc only when user actually
>> accesses it. This data needs to be
>> static in nature, meaning I get one error and I write it to a file somehow
>> and user can see it anytime.
>>
>> I hope I have described the situation clearly. I have explored some
>> mechanism like ioctls, mmaping the
>> kernel buffer etc but all these would require the user module to poll or
>> notified somehow by kernel that
>> the data is available. I dont want the user module to poll.
>>
>>
>> -Leo.
>>
>
> When we do a printk it writes to kernel log buffer, correct? This is real in
> time operation i.e. as soon as we do a
> printk the messages get logged. Now this log file can be accesses from
> /var/log/messages right? How is this done?
>
> I want to so something similar, so I can log my messages to a seprate file
> which is going to stay around so user can
> see at across reboots as well.
>
>
>
> -Leo.
>
>
And I have been reading that 'It is a bad..bad thing to access files from kernel space'
since I started doing Linux stuff.
_Leo.
I am aware of other legitimate mechanisms as I have described on my origianl post.
It is just that I have certain constraints under which I cant use many of the methods
since I dont want to user space entity to do polling or get signal from kernel.
-Leo.
