Re: [PATCH] net: stmmac: ensure jumbo_frm error return is correctly checked for -ve value

[David Miller]

From: Colin King <colin.king@xxxxxxxxxxxxx>
Date: Fri,  2 Jun 2017 15:58:27 +0100

> From: Colin Ian King <colin.king@xxxxxxxxxxxxx>
> 
> 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.
> 
> Detected by CoverityScan, CID#1238760 ("Macro compares unsigned to 0")
> 
> Signed-off-by: Colin Ian King <colin.king@xxxxxxxxxxxxx>

Like others have suggested, probably making 'entry' signed is
a better fix.

I was initially worried that STMMAC_GET_ENTRY() might become
more expensive if it was implemented using '%' but it is using
'and' masking instead which doesn't have that kind of problem.