netdev - Re: [PATCH v3 net-next 09/21] net: usb: aqc111: Implement RX data path

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Message-Id: <20181122.111257.148155241898152803.davem@davemloft.net>
Date:   Thu, 22 Nov 2018 11:12:57 -0800 (PST)
From:   David Miller <davem@...emloft.net>
To:     Igor.Russkikh@...antia.com
Cc:     linux-usb@...r.kernel.org, netdev@...r.kernel.org, andrew@...n.ch,
        Dmitry.Bezrukov@...antia.com
Subject: Re: [PATCH v3 net-next 09/21] net: usb: aqc111: Implement RX data
 path

From: Igor Russkikh <Igor.Russkikh@...antia.com>
Date: Wed, 21 Nov 2018 10:13:39 +0000

> +	desc_hdr = *(u64 *)skb_tail_pointer(skb);
> +	le64_to_cpus(&desc_hdr);

This is:

	desc_hdr = le64_to_cpup(skb_tail_pointer(skb));

> +	/* Get the first RX packet descriptor */
> +	pkt_desc = (u64 *)(skb->data + desc_offset);
> +
> +	while (pkt_count--) {
> +		u32 pkt_len = 0;
> +		u32 pkt_len_with_padd = 0;
> +
> +		le64_to_cpus(pkt_desc);

Probably better to load the translated value into a local variable
once:

		u64 cpu_desc = le64_to_cpup(pkt_desc);

and then use 'cpu_desc' instead of dereferencing "*pkt_desc" over and
over again.

> +		/* Clone SKB */
> +		new_skb = skb_clone(skb, GFP_ATOMIC);
> +
> +		if (!new_skb)
> +			goto err;
> +
> +		new_skb->len = pkt_len;
> +		skb_pull(new_skb, AQ_RX_HW_PAD);
> +		skb_set_tail_pointer(new_skb, new_skb->len);
> +
> +		new_skb->truesize = new_skb->len + sizeof(struct sk_buff);

I see lots of USB drivers doing this, but it's not correct.

We have a SKB_TRUESIZE() macro, please use it.