Re: opening linux char device file in user thread.

["P.Manohar" <pmanohar@lantana.cs.iitm.ernet.in>]

thanks for help, it is working now, I opened the char file before the 
thread starts.

On Thu, 4 Aug 2005, Bhanu Kalyan Chetlapalli wrote:

> On 8/4/05, P.Manohar <pmanohar@lantana.cs.iitm.ernet.in> wrote:
> > hai,
> >
> >    I have written a daemon which is running in user space, will send some
> > data periodically to kernel space. This I have done with the help of a
> > device file.
> >
> >  It is working, but I want to apply threads mechanism in that daemon. But
> > when I split that daemon functionality into a thread and a original
> > process. I am unable to
> > open the device file. This is happening in both places(either in thread or
> > original process).
>
> Try opening the device, get the FD and THEN spawn the thread. this
> will help, as the device is opened only once as far as the driver is
> concerned. The presence of usage from the thread is felt only in the
> reference count of the fd (which should be transparent to user space
> and the device driver). Race conditions are assumed to be taken care
> of in the kernel module though.
>
> The other way is to open device, write data, close device every time u
> write something. This is beneficial if the time between the writes is
> seperated by more than a minute. There will be no races etc to take
> care of.
>
> > The device is opening  when threading is not there.
> >
> > Can anybody suggest me?
> >
> > Regards,
> > P.Manohar.
>
> Bhanu.
>
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