Re: [Resend][PATCH] usb driver for intellon int51x1 based PLC like devolo dlan duo

["Peter Holik" <peter@holik.at>]

>> +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;

cu Peter