On Wed, 2006-07-26 at 16:54 +0200, Christian Boon wrote:
> Arjan van de Ven wrote:
>
> >On Wed, 2006-07-26 at 16:25 +0200, Christian Boon wrote:
> >
> >
> >>Hello,
> >>
> >>i've got a question about a page fault:
> >>
> >>If have a kernel module that puts data in an array from an external fifo
> >>after an interrupt:
> >>
> >>static void *datapointer;
> >>__u16 Data[325];
> >>
> >>for (Counter = 0 ; Counter < 325; Counter++)
> >>{
> >> Data[Counter] = readw(datapointer);
> >>}
> >>wake_up_interruptible(&waitqueue);
> >>
> >>My application is sleeping on the waitqueue.
> >>
> >>in the application:
> >>
> >>typedef unsigned char u8;
> >>u8 VideoData[650];
> >>
> >>bytes = read(fd, VideoData, sizeof(u8));
> >>
> >>So i want to store the array u16 and read in userspace u8.
> >>is this a problem? maybe alignment?
> >>
> >>sometimes i get this error:
> >>
> >>PraxisSC: unhandled page fault at pc=0x40026df0, lr=0x40089790 (bad
> >>
> >>
> >
> >that looks like a bug in your read function... unfortunately you didn't
> >provide a pointer to your source so it's hard for us to point that out
> >in more detail...
> >
> >Greetings,
> > Arjan van de Ven
> >
> ssize_t EribRead(struct file *filp, char *buf, size_t count, loff_t *offp)
> {
> interruptible_sleep_on(&waitqueue);
> copy_to_user(buf, &Data, sizeof(Data));
> }
you're not returning a return value.. that'll blow up bigtime
(and you're not handling error conditions either, and
interruptible_sleep_on() has many nasty corner cases that you don't
handle, you really shouldn't use that API)
--
Kernelnewbies: Help each other learn about the Linux kernel.
Archive: http://mail.nl.linux.org/kernelnewbies/
FAQ: http://kernelnewbies.org/faq/
