Date: Fri, 3 Jun 2005 15:35:52 +0200 From: Seb <sebastien.b@swissinfo.org> To: hselasky@c2i.net Cc: freebsd-usb@freebsd.org Subject: Re: usbd_bulk_transfer returns 1 (USBD_IN_PROGRESS) ?! Message-ID: <200506031535.53126.sebastien.b@swissinfo.org> In-Reply-To: <200505281531.14351.hselasky@c2i.net> References: <200505252120.22408.sebastien.b@swissinfo.org> <200505271331.05132.sebastien.b@swissinfo.org> <200505281531.14351.hselasky@c2i.net>
next in thread | previous in thread | raw e-mail | index | archive | help
On Saturday 28 May 2005 15:31, Hans Petter Selasky wrote:
> On Friday 27 May 2005 13:31, Seb wrote:
> > But I didn't fix it with mutexes, I used semaphores instead.
> > I initialize a semaphore with a value equal to 1 and then, before the USB
> > transfers, I do :
>
> while(entered)
> {
>
> > mtx_unlock(&Giant);
> > sema_wait(&sc->usb_tx_sema);
> > mtx_lock(&Giant);
>
> }
> entered = 1;
>
> > And after the USB transfers :
> > sema_post(&sc->usb_tx_sema);
>
> entered = 0;
I'm afraid I don't understand why I should do that.
Moreover, if the functions are never called concurrently, the semaphore value
will never go down...
> > Is this OK ?
>
> I think it is better you use "sx_xlock", "sx_xunlock" and "sx_init".
> See "man sx".
What would be the difference with mutexes ? Only so that I can sleep while
holding the lock ?
Is calling sx_xlock() safe while holding Giant ? The manual page does not
specify this...
> If you do things via callback you can remove "sc->tx_queues[]" and
> associated functions.
No, these are also part of Conexant's proprietary protocol.
> I think you will get better performance using
> callbacks. And most importantly, you are no longer blocking the callers of
> those functions that send packets.
With the device's protocol which require chained transfers, it will be a mess.
That's why I use those software interrupt handlers.
Regards,
Sebastien
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?200506031535.53126.sebastien.b>