Re: ioctl()

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you told that

> fd = open("/dev/mydev", O_RDONLY);

but i found that extra one parameter...see

fd = open (dev_name, O_RDWR /*required*/| O_NONBLOCK,0);
`
can you explain this?



--- On Sat, 3/1/09, Robert P. J. Day <rpjday@xxxxxxxxxxxxxx> wrote:
From: Robert P. J. Day <rpjday@xxxxxxxxxxxxxx>
Subject: Re: ioctl()
To: "Rohit Sharma" <imreckless@xxxxxxxxx>
Cc: "rishi agrawal" <postrishi@xxxxxxxxx>, shariefbe@xxxxxxxxxxx, "Kernel newbies" <kernelnewbies@xxxxxxxxxxxx>
Date: Saturday, 3 January, 2009, 8:42 PM

On Sat, 3 Jan 2009, Rohit Sharma wrote:

> ioctls are also known as generic system calls. Its a simple switch
> case implementation inside a device.
> you send command and argument through ioctls as parameters.
> Its a way you use to interact with the device itself.
>
> for using it just open the device and use its fd to invoke ioctls.
>
> for eg.
>
> fd = open("/dev/mydev", O_RDONLY);
>
> ioctl(fd, cmd, argument);
>
>
> its internal representation is something like:
>
> ioctl( struct file *, struct inode*, unsigned int cmd, unsigned long arg)
> {
>     switch(cmd) {
>                          case 1:  .......
>                          case 2:  .........
>      }
> }
>
> for more details refer Beginning Linux Programming.
> I hope that helps.

  the last i heard, while ioctl's aren't going away any time soon,
they're deprecated in favour of ... uh, files under /sys?  am i
remembering that correctly?  in short, if you're already working with
an ioctl-based code base, keep doing that.  but if you have the
opportunity to design some kernel code from scratch, use the sysfs.

  or am i way off base here?

rday
--

========================================================================
Robert P. J. Day
Linux Consulting, Training and Annoying Kernel Pedantry:
    Have classroom, will lecture.

http://crashcourse.ca                          Waterloo, Ontario, CANADA
========================================================================

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