Arjan van de Ven wrote:
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)
Ok so what functions should i use to synchronise my application with the
kernel module?
And when i call copy_to_user() and the user space pointer is invalid, it
should return a
negative value right (-EFAULT) and shouldnt give an unhandled page fault.
Chris.
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