You might want to take a look at the bpf pseudo device and how it
handles polls int bpf.c. You need to use the selrecord() and
selwakeup() functions.
Check out:
http://www.freebsd.org/cgi/cvsweb.cgi/src/sys/net/
On May 26, 2005, at 6:00 PM, Aziz Kezzou wrote:
Aziz Kezzou wrote:
Hi all,
I am trying to implement a small kld pseudo-device driver on
FreeBSD 5.3 that
behaves just like a socket with regards to the select system call.
Currently, I am using the sample echo pseudo-device driver from
http://www.freebsd.org/doc/en_US.ISO8859-1/books/arch-handbook/
driverbasics-char.html
as an example. However, whenever I call select on the file
descriptor of "/dev/echo" it always returns even when there is
no data
to be read.
I looked at the socket code and it looks like I need to provide
my own
"fo_select" function in the fileops data structure. Am i right ?
How
do I do that ? The sample echo pseudo-device driver above uses
"struct cdevsw" instead...
Thanks
-aziz
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look at spec_poll()
I beleive that when your device is opened the fileops{} will
point to the spec ops and you're code will be entered via
spec_poll() - now you just need to implement the poll/select notion
for your device.
Thanks,
Actually, il turned out to be very simple.
I needed only to provide a "d_poll" function as part of the structure
cdevsw, as follows :
/* Character device entry points */
static struct cdevsw echo_cdevsw = {
.d_version = D_VERSION,
.d_open = echo_open,
.d_close = echo_close,
.d_read = echo_read,
.d_write = echo_write,
.d_poll = echo_poll,
.d_name = "echo",
};
with echo_poll :
static int
echo_poll(struct cdev *dev, int events, struct thread *td)
{
uprintf( "echo_poll called : data_available = %d!\n",
data_available );
if(data_available == 0)
return 0;
data_available = 0;
return 1;
}
Now the question is, if I don't have any data available when select
(i.e d_poll ) is called, how do I notify select when data arrives ?
looks like "d_poll" is called only once (the name is a bit misleading
here ;-) , isn't it ?
Any hints ?
Thanks.
-aziz
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