Date: Sun, 1 Feb 2009 11:14:32 -0800 From: Andrew Thompson <thompsa@FreeBSD.org> To: Hans Petter Selasky <hselasky@c2i.net> Cc: freebsd-usb@freebsd.org Subject: Re: USB2 patches Message-ID: <20090201191432.GD32503@citylink.fud.org.nz> In-Reply-To: <200902012001.06914.hselasky@c2i.net> References: <200902011220.18745.hselasky@c2i.net> <20090201.112756.1320088159.imp@bsdimp.com> <200902011938.48670.hselasky@c2i.net> <200902012001.06914.hselasky@c2i.net>
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On Sun, Feb 01, 2009 at 08:01:05PM +0100, Hans Petter Selasky wrote:
> Hi Andrew,
>
> Regarding using taskqueues.
>
> Yes - USB2 can use taskqueues, but I would very much like to have the original
> queueing mechanism intact.
Can you explain this further? What is t0 vs t1?
A taskqueue will execute tasks sequentially, why do you need to pass two
tasks in at a time?
> How about:
>
> struct task *
> tasqueue_enqueue_pair(struct taskqueue *queue, struct task *t0, struct task
> *t1);
>
> Which does something similar to this:
>
> void *
> usb2_proc_msignal(struct usb2_process *up, void *_pm0, void *_pm1)
> {
> struct usb2_proc_msg *pm0 = _pm0;
> struct usb2_proc_msg *pm1 = _pm1;
> struct usb2_proc_msg *pm2;
> uint32_t d;
> uint8_t t;
>
> mtx_assert(up->up_mtx, MA_OWNED);
>
> t = 0;
>
> if (pm0->pm_qentry.tqe_prev) {
> t |= 1;
> }
> if (pm1->pm_qentry.tqe_prev) {
> t |= 2;
> }
> if (t == 0) {
> /*
> * No entries are queued. Queue "pm0" and use the existing
> * message number.
> */
> pm2 = pm0;
> } else if (t == 1) {
> /* Check if we need to increment the message number. */
> if (pm0->pm_num == up->up_msg_num) {
> up->up_msg_num++;
> }
> pm2 = pm1;
> } else if (t == 2) {
> /* Check if we need to increment the message number. */
> if (pm1->pm_num == up->up_msg_num) {
> up->up_msg_num++;
> }
> pm2 = pm0;
> } else if (t == 3) {
> /*
> * Both entries are queued. Re-queue the entry closest to
> * the end.
> */
> d = (pm1->pm_num - pm0->pm_num);
>
> /* Check sign after subtraction */
> if (d & 0x80000000) {
> pm2 = pm0;
> } else {
> pm2 = pm1;
> }
>
> TAILQ_REMOVE(&up->up_qhead, pm2, pm_qentry);
> } else {
> pm2 = NULL; /* panic - should not happen */
> }
>
> DPRINTF(" t=%u, num=%u\n", t, up->up_msg_num);
>
> /* Put message last on queue */
>
> pm2->pm_num = up->up_msg_num;
> TAILQ_INSERT_TAIL(&up->up_qhead, pm2, pm_qentry);
>
> /* Check if we need to wakeup the USB process. */
>
> if (up->up_msleep) {
> up->up_msleep = 0; /* save "cv_signal()" calls */
> usb2_cv_signal(&up->up_cv);
> }
> return (pm2);
> }
>
> --HPS
> _______________________________________________
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