On Sat, 18 Apr 2009, Peter Holik wrote:
> >> +static struct sk_buff *int51x1_tx_fixup(struct usbnet *dev,
> >> + struct sk_buff *skb, gfp_t flags)
> >> +{
> >> + int pack_len = skb->len;
> >> + int headroom = skb_headroom(skb);
> >> + int tailroom = skb_tailroom(skb);
> >> + int need_tail = 0;
> >> + __le16 *len;
> >> +
> >> + /*
> >> + * usbnet would send a ZLP if packetlength mod urbsize == 0 for us,
> >> + * but we need to know ourself, because this would add to the length
> >> + * we send down to the device...
> >> + */
> >> + if (!((pack_len + INT51X1_HEADER_SIZE) % dev->maxpacket))
> >> + need_tail = 1;
> >> +
> >> + /* if packet and our header is smaler than 64 pad to 64 (+ ZLP) */
> >> + if ((pack_len + INT51X1_HEADER_SIZE + need_tail) < dev->maxpacket + 1)
> >> + need_tail = dev->maxpacket + 1 - pack_len - INT51X1_HEADER_SIZE;
> >
> > This is totally crazy code fragment, first need_tail is used like a
> > boolean? But on the same some +1 scalar trick is being done? Is there some
> > reason why DIV_ROUND_UP (linux/kernel.h) won't do what you want here and
> > then you can trivally find diff = new - old ?
> >
>
> maybe this version is not so crazy for you?
>
> /* if packet and our header is smaler than 64 pad to 64 (+ ZLP) */
> if ((pack_len + INT51X1_HEADER_SIZE) < dev->maxpacket)
> need_tail = dev->maxpacket - pack_len - INT51X1_HEADER_SIZE + 1;
> /*
> * usbnet would send a ZLP if packetlength mod urbsize == 0 for us,
> * but we need to know ourself, because this would add to the length
> * we send down to the device...
> */
> else if (!((pack_len + INT51X1_HEADER_SIZE) % dev->maxpacket))
> need_tail = 1;
Certainly looks more obvious, having that + need_tail and the related + 1
on the other side of the condition made the original very hard to read
(and I failed to read it correctly which was the reason for the wrong
DIV_ROUND_UP comment I made). This one is much better. I guess adding
a temporary var for pack_len + INT51X1_HEADER_SIZE would also make it
somewhat nicer looking.
--
i.
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