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Date: Wed, 09 Sep 2015 20:34:27 +0200 From: Rasmus Villemoes <linux@...musvillemoes.dk> To: Joe Perches <joe@...ches.com> Cc: Sebastian Hesselbarth <sebastian.hesselbarth@...il.com>, netdev@...r.kernel.org, linux-kernel@...r.kernel.org Subject: Re: [PATCH 3/4] net: mv643xx_eth: use kzalloc On Wed, Sep 09 2015, Joe Perches <joe@...ches.com> wrote: > On Wed, 2015-09-09 at 10:38 +0200, Rasmus Villemoes wrote: >> The double memset is a little ugly; using kzalloc avoids it altogether. > [] >> diff --git a/drivers/net/ethernet/marvell/mv643xx_eth.c b/drivers/net/ethernet/marvell/mv643xx_eth.c > [] >> @@ -1859,14 +1859,11 @@ oom: >> return; >> } >> >> - mc_spec = kmalloc(0x200, GFP_ATOMIC); >> + mc_spec = kzalloc(0x200, GFP_ATOMIC); >> if (mc_spec == NULL) >> goto oom; >> mc_other = mc_spec + (0x100 >> 2); > > This sure looks wrong as it sets a pointer > to unallocated memory. > >> - memset(mc_spec, 0, 0x100); >> - memset(mc_other, 0, 0x100); > > So this does a memset of random memory. > Huh? mc_spec and mc_other are u32*, we allocate 0x200 = 512 bytes = 128 u32s, and pointer arithmetic makes mc_other point to the latter 64. Then the memory is cleared 256 bytes at a time. It's unusual and slightly obfuscated code, but I don't think it's wrong. > > for (i = 0; i < 0x100; i += 4) { > wrl(mp, SPECIAL_MCAST_TABLE(mp->port_num) + i, mc_spec[i >> 2]); > wrl(mp, OTHER_MCAST_TABLE(mp->port_num) + i, mc_other[i >> 2]); > } I'd probably have written that as for (i = 0; i < 64; ++i) { wrl(mp, SPECIAL_MCAST_TABLE(mp->port_num) + 4*i, mc_spec[i]); wrl(mp, OTHER_MCAST_TABLE(mp->port_num) + 4*i, mc_other[i]); } but again, I don't think it's wrong [haven't checked what SPECIAL_MCAST_TABLE/OTHER_MCAST_TABLE do, though]. Rasmus -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
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