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Date: Wed, 13 Jun 2012 08:21:18 -0700 From: Grant Grundler <grantgrundler@...il.com> To: Takuya Yoshikawa <takuya.yoshikawa@...il.com> Cc: Akinobu Mita <akinobu.mita@...il.com>, Takuya Yoshikawa <yoshikawa.takuya@....ntt.co.jp>, akpm@...ux-foundation.org, bhutchings@...arflare.com, grundler@...isc-linux.org, arnd@...db.de, benh@...nel.crashing.org, avi@...hat.com, mtosatti@...hat.com, linux-net-drivers@...arflare.com, netdev@...r.kernel.org, linux-kernel@...r.kernel.org, linux-arch@...r.kernel.org, kvm@...r.kernel.org Subject: Re: [PATCH 2/5] drivers/net/ethernet/dec/tulip: Use standard __set_bit_le() function On Wed, Jun 13, 2012 at 7:00 AM, Takuya Yoshikawa <takuya.yoshikawa@...il.com> wrote: > On Wed, 13 Jun 2012 22:31:13 +0900 > Akinobu Mita <akinobu.mita@...il.com> wrote: > >> >> Should this hash_table be converted from u16 hash_table[32] to >> >> DECLARE_BITMAP(hash_table, 16 * 32) to ensure that it is aligned >> >> on long-word boundary? >> > >> > I think hash_table is already long-word aligned because it is placed >> > right after a pointer. >> >> I recommend converting to proper bitmap. Because such an implicit >> assumption is easily broken by someone touching this function. > > Do you mean something like: > DECLARE_BITMAP(__hash_table, 16 * 32); > u16 *hash_table = (u16 *)__hash_table; > ? > > Grant, what do you think about this? Hi Takuya, two thoughts: 1) while I agree with Akinobu and thank him for pointing out a _potential_ alignment problem, this is a separate issue and your existing patch should go in anyway. There are probably other drivers with _potential_ alignment issues. Akinobu could get credit for finding them by submitting patches after reviewing calls to set_bit and set_bit_le() - similar to what you are doing now. 2) I generally do not like declaring one type and then using an alias of a different type to reference the same memory address. We have a simple alternative since hash_table[] is indexed directly only in one hunk of code: for (i = 0; i < 32; i++) { *setup_frm++ = ((u16 *)hash_table)[i]; *setup_frm++ = ((u16 *)hash_table)[i]; } thanks, grant > > Takuya > > > === > drivers/net/ethernet/dec/tulip/tulip_core.c: > > static void build_setup_frame_hash(u16 *setup_frm, struct net_device *dev) > { > struct tulip_private *tp = netdev_priv(dev); > u16 hash_table[32]; > ... > } > > drivers/net/ethernet/dec/tulip/de2104x.c: > > static void build_setup_frame_hash(u16 *setup_frm, struct net_device *dev) > { > struct de_private *de = netdev_priv(dev); > u16 hash_table[32]; > ... > } -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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