Re: [Qemu-devel] [PATCH RFC] ps2: set the keybord output buffer size as the same as kernel

[Gonglei (Arei)]

> 
> "Gonglei (Arei)" <address@hidden> wrote:
> >>   Hi,
> >>
> >> > Anything bigger than 16bytes, no?  And that is the whole point that we
> >> > are talking about?  Or the 16bytes that we are using can be at any place
> >> > on the buffer?
> >>
> >> Yes.  It's a ring buffer, with rptr pointing to the first used element
> >> and wptr pointing to the first free element.
> >>
> >> So, what we need is a function to move the content we are interested
> >> (between rptr and wptr) in to the head of the ring buffer, set rptr to
> >> 0, set wptr to count.  We obviously need to do that in post_load(), but
> >> as I've noticed meanwhile also in pre_save, otherwise old qemu will get
> >> things wrong in case the buffer is wrapped (rptr > wptr).
> >>
> > Hi, Gerd. Maybe we just need to do in post_load(). Such as the follow code:
> >
> > static int ps2_kbd_post_load(void* opaque, int version_id)
> > {
> >     PS2KbdState *s = (PS2KbdState*)opaque;
> 
> cast not needed.
This is the original code, I don't change it. Maybe I should post the diff 
file, Sorry.

> 
> >     PS2State *ps2 = &s->common;
> >     PS2Queue *q = &ps2->queue;
> >     int size;
> >     int i;
> >
> >     if (version_id == 2)
> >         s->scancode_set=2;
> >     /* the new version id for this patch */
> >     if (version_id == 4) {
> >         return 0;
> >     }
> >     /* set the useful data buffer queue size, < PS2_QUEUE_SIZE */
> >     size = MIN(q->count, PS2_QUEUE_SIZE);
> >     printf(" ==kbd: rptr: %d, wptr: %d, count: %d, size: %d\n", q->rptr,
> q->wptr, q->count, size);
> >     for (i = 0; i < size; i++) {
> >         /* move the queue elements to the start of data array */
> >         q->data[i] = q->data[q->rptr];
> 
> It is me, or this don't work if the destination and source regions
> overlap?  Yes, it depens on how it overlaps.
Good catch, Juan, Thanks. It should use a temp data array to save the q->data[] 
value,
Such as below:
    int size;
    int i;
    int tmp_data[PS2_QUEUE_SIZE];
    
    /* set the useful data buffer queue size, < PS2_QUEUE_SIZE */
    size = MIN(q->count, PS2_QUEUE_SIZE);
    printf(" ==kbd: rptr: %d, wptr: %d, count: %d, size: %d\n", q->rptr, 
q->wptr, q->count, size);
    for (i = 0; i < size; i++) {
        /* move the queue elements to the tmp data array */
        tmp_data[i] = q->data[q->rptr];
        if (++q->rptr == 256) {
            q->rptr = 0;
        }
    }
    for (i = 0; i < size; i++) {
        /* move the queue elements to the start of data array */
        q->data[i] = tmp_data[i];
    }
    /* reset rptr/wptr/count */
    q->rptr = 0;
    q->wptr = size;
    q->count = size;
    s->update_irq(s->update_arg, q->count != 0);
    
    return 0;
}

Best regards,
-Gonglei