Very Computer

by **Fredric Moreniu** » Wed, 05 Sep 2001 21:29:02

Hello,

I am writing a custom char device driver and would like to check which
file access mode (reading only ,writing only, etc.) a process that opens
the char file requests. Which member of the file data structure holds this
information and which are the possible types?

Thanks,

Fredric Morenius

by **Kasper Dupon** » Wed, 05 Sep 2001 23:27:31

> Hello,

> I am writing a custom char device driver and would like to check which
> file access mode (reading only ,writing only, etc.) a process that opens
> the char file requests. Which member of the file data structure holds this
> information and which are the possible types?

The f_mode field. I suggest you see how
sys_read and sys_write check that field.
(linux/fs/read_write.c)

> Thanks,

> Fredric Morenius

--
Kasper Dupont

by **Pete Zaitc** » Thu, 06 Sep 2001 00:13:59

Quote:> > I am writing a custom char device driver and would like to check which
> > file access mode (reading only ,writing only, etc.) a process that opens
> > the char file requests. Which member of the file data structure holds this
> > information and which are the possible types?

> The f_mode field. I suggest you see how
> sys_read and sys_write check that field.
> (linux/fs/read_write.c)

Kasper's answer is correct for testing permissions, but
this is not how I interpret Fredric's question.
He probably was looking for something like this:

static int ymf_open(struct inode *inode, struct file *file)
{
.................
if (file->f_mode & FMODE_WRITE) {
.... Program device for write
}
if (file->f_mode & FMODE_READ) {
.... Program device for read
}
return 0;

Quote:}

Note that both flags may be set if the process is using O_RDWR.

-- Pete

Very Computer

Which member of the file data struct. holds file access type?

Which member of the file data struct. holds file access type?

Which member of the file data struct. holds file access type?

Which member of the file data struct. holds file access type?