Using select()/poll() in device driver

Question

I have a driver, which handles several TCP connections.

Is there a way to perform something similar to user space application api's select/poll()/epoll() in kernel given a list of struct sock's?

Thanks

Answer 1

You may want to write your own custom sk_buff handler, which calls the kernel_select() that tries to lock the semaphore and does a blocking wait when the socket is open.

Not sure if you have already gone through this link Simulate effect of select() and poll() in kernel socket programming

Answer 2

On the kernel side it's easy to avoid using sys_epoll() interface outright. After all, you've got a direct access to kernel objects, no need to jump through hoops.

Each file object, sockets included, "overrides" a poll method in its file_operations "vtable". You can simply loop around all your sockets, calling ->poll() on each of them and yielding periodically or when there's no data available.

If the sockets are fairly high traffic, you won't need anything more than this.

A note on the API:

poll() method requires a poll_table() argument, however if you do not intend to wait on it, it can safely be initialized to null:

poll_table pt;
init_poll_funcptr(&pt, NULL);
...
// struct socket *sk;
...
unsigned event_mask = sk->ops->poll(sk->file, sk, &pt);

If you do want to wait, just play around with the callback set into poll_table by init_poll_funcptr().