On Sat, 3 Jun 2017, Colin Ian King wrote:
> On 03/06/17 16:55, Andy Shevchenko wrote:
> > On Fri, Jun 2, 2017 at 5:58 PM, Colin King <colin.king@xxxxxxxxxxxxx> wrote:
> >> The current comparison of entry < 0 will never be true since entry is an
> >> unsigned integer. Cast entry to an int to ensure -ve error return values
> >> from the call to jumbo_frm are correctly being caught.
> >
> >> if (unlikely(is_jumbo) && likely(priv->synopsys_id <
> >> DWMAC_CORE_4_00)) {
> >> entry = priv->hw->mode->jumbo_frm(tx_q, skb, csum_insertion);
> >> - if (unlikely(entry < 0))
> >> + if (unlikely((int)entry < 0))
> >
> > It feels like a hiding some other issue.
> >
>
> The alternative is:
>
> int rc = priv->hw->mode->jumbo_frm(tx_q, skb, csum_insertion);
> if (unlikely(rc < 0))
> goto dma_map_err;
>
> entry = rc;
>
> however, that is effectively the same. The cast I'm using is a well used
> idiom in the kernel, it used in almost a hundred similar cases.
>
> git grep "< 0" | grep "(int)" | wc -l
> 95
Does entry really have to be unsigned? The jumbo_frm function returns an
int, not an unsigned int, so it seems unpleasant to make it unsigned
prematurely just to put a cast afterwards. The remaining computation
seems to involve only small numbers.
julia
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