Which include should I have to have these macros IS_BLK and IS_CHR to
run. I grepped the all the source files and I didnt find the occurance of
these two functions ( macros).
Please give me the usage of this...
thanks a lot,
raghu
On Fri, 22 Nov 2002, Jan Hudec wrote:
> On Thu, Nov 21, 2002 at 06:39:37PM -0500, Raghu R. Arur wrote:
> > Hi,
> >
> > I have a problem. In my module I am not able to differentiate between
> > whether requests are coming from a block device or character device.
> >
> > I am running my module on vmware and the keyboard hits are read thru
> > ptty. The major number of ptty and the hard disk are both 3. I am blocking
> > read system call in my module and I want to deal with the requests
> > pertaining to the disk only. So given a file descriptor I am able to get
> > the inode value and also the major and minor number of the device to which
> > the request has to go.
> >
> > So in order to service only the requests of the disk i have an if
> > statement
> >
> > if(inode && major == 3)
> > {
> > do my sys_read
> > }
> > else
> > {
> > do original sys_read
> > }
> >
> >
> > but every keystroke evaluates to true and does my sys_read section. I
> > thought that character devices do not have inode and the ptty requests
> > evaluate to false at if statement. But it is not happening so...
> >
> > am i missing something...
> >
> > please help me.
> >
> > thanks,
> > raghu
>
> Every device must have an inode. Actually sys_read is called on file and
> file must have an inode. It is the device inode, that is it is the inode
> that makes /dev/tty<n> appear on your filesystem (even if it may be
> created on the fly by kernel, it's still an inode in memory). In this
> inode, the i_dev should contain the device number and the i_mode should
> contain the file type, in this case either IS_CHR(i_mode) or
> IS_BLK(i_mode) should be true.
>
> What about intercepting the function registered for char major 3?
> Best way would be to patch the kernel a bit to make a hook there.
> However if you find the file_operations structure registered for the
> device, you can just replace the pointer in there.
>
> PS: Please don't send new topics as a reply to unrelated message. Many
> people have threaded mail readers and such mail tend to get lost in
> threads.
>
> -------------------------------------------------------------------------------
> Jan 'Bulb' Hudec <bulb@ucw.cz>
>
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