USB2 patches

[Andrew Thompson]

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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