From: Arnd Bergmann <arnd@arndb.de>
To: linux-arm-kernel@lists.infradead.org
Cc: Alan Stern <stern@rowland.harvard.edu>,
Alexander Holler <holler@ahsoftware.de>,
gregkh@suse.de, Nicolas Pitre <nico@fluxnic.net>,
linux-usb@vger.kernel.org, lkml <linux-kernel@vger.kernel.org>,
Rabin Vincent <rabin@rab.in>
Subject: Re: [PATCH] USB: ehci: use packed,aligned(4) instead of removing the packed attribute
Date: Mon, 20 Jun 2011 22:09:34 +0200 [thread overview]
Message-ID: <201106202209.35152.arnd@arndb.de> (raw)
In-Reply-To: <Pine.LNX.4.44L0.1106201436430.2113-100000@iolanthe.rowland.org>
On Monday 20 June 2011 20:39:02 Alan Stern wrote:
> On Mon, 20 Jun 2011, Alexander Holler wrote:
>
> > I see it that way: packed is needed to be sure that at least for struct
> > ehci_regs there are no padding bytes inbetween the members.
>
> But is it really needed?
No. When the structure is marked packed, it's broken because it relies
on undefined behavior. If it's not packed, there is no problem.
> > It might
> > work without, but that depends on the compiler (-version, architecture,
> > whatever).
>
> Have there ever been any combinations of compiler, version,
> architecture, whatever, that had unwanted padding bytes in this
> structure?
Only on compilers that are not able to build Linux kernels anyway.
Arnd
WARNING: multiple messages have this Message-ID (diff)
From: arnd@arndb.de (Arnd Bergmann)
To: linux-arm-kernel@lists.infradead.org
Subject: [PATCH] USB: ehci: use packed, aligned(4) instead of removing the packed attribute
Date: Mon, 20 Jun 2011 22:09:34 +0200 [thread overview]
Message-ID: <201106202209.35152.arnd@arndb.de> (raw)
In-Reply-To: <Pine.LNX.4.44L0.1106201436430.2113-100000@iolanthe.rowland.org>
On Monday 20 June 2011 20:39:02 Alan Stern wrote:
> On Mon, 20 Jun 2011, Alexander Holler wrote:
>
> > I see it that way: packed is needed to be sure that at least for struct
> > ehci_regs there are no padding bytes inbetween the members.
>
> But is it really needed?
No. When the structure is marked packed, it's broken because it relies
on undefined behavior. If it's not packed, there is no problem.
> > It might
> > work without, but that depends on the compiler (-version, architecture,
> > whatever).
>
> Have there ever been any combinations of compiler, version,
> architecture, whatever, that had unwanted padding bytes in this
> structure?
Only on compilers that are not able to build Linux kernels anyway.
Arnd
next prev parent reply other threads:[~2011-06-20 20:11 UTC|newest]
Thread overview: 124+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-04-27 14:34 [PATCH] echi: remove structure packing from ehci_def Rabin Vincent
2011-04-27 14:34 ` Rabin Vincent
2011-04-27 15:15 ` Sergei Shtylyov
2011-04-27 15:15 ` Sergei Shtylyov
2011-04-27 15:37 ` [PATCHv2] " Rabin Vincent
2011-04-27 15:37 ` Rabin Vincent
2011-06-16 16:17 ` [PATCH] USB: ehci: use packed,aligned(4) instead of removing the packed attribute Alexander Holler
2011-06-16 16:17 ` [PATCH] USB: ehci: use packed, aligned(4) " Alexander Holler
2011-06-16 17:09 ` [PATCH] USB: ehci: use packed,aligned(4) " Alan Stern
2011-06-16 17:09 ` Alan Stern
2011-06-16 17:55 ` Arnd Bergmann
2011-06-16 17:55 ` [PATCH] USB: ehci: use packed, aligned(4) " Arnd Bergmann
2011-06-16 19:25 ` [PATCH] USB: ehci: use packed,aligned(4) " Alexander Holler
2011-06-16 19:25 ` Alexander Holler
2011-06-16 19:46 ` Alan Stern
2011-06-16 19:46 ` Alan Stern
2011-06-16 20:10 ` Alexander Holler
2011-06-16 20:10 ` Alexander Holler
2011-06-16 20:20 ` Arnd Bergmann
2011-06-16 20:20 ` [PATCH] USB: ehci: use packed, aligned(4) " Arnd Bergmann
2011-06-19 15:02 ` [PATCH] USB: ehci: use packed,aligned(4) " Nicolas Pitre
2011-06-19 15:02 ` [PATCH] USB: ehci: use packed, aligned(4) " Nicolas Pitre
2011-06-19 19:00 ` [PATCH] USB: ehci: use packed,aligned(4) " Alan Stern
2011-06-19 19:00 ` Alan Stern
2011-06-19 20:02 ` Arnd Bergmann
2011-06-19 20:02 ` [PATCH] USB: ehci: use packed, aligned(4) " Arnd Bergmann
2011-06-19 20:11 ` [PATCH] USB: ehci: use packed,aligned(4) " Arnd Bergmann
2011-06-19 20:11 ` [PATCH] USB: ehci: use packed, aligned(4) " Arnd Bergmann
2011-06-19 21:39 ` [PATCH] USB: ehci: use packed,aligned(4) " Nicolas Pitre
2011-06-19 21:39 ` [PATCH] USB: ehci: use packed, aligned(4) " Nicolas Pitre
2011-06-19 21:27 ` [PATCH] USB: ehci: use packed,aligned(4) " Nicolas Pitre
2011-06-19 21:27 ` [PATCH] USB: ehci: use packed, aligned(4) " Nicolas Pitre
2011-06-20 15:03 ` [PATCH] USB: ehci: use packed,aligned(4) " Alan Stern
2011-06-20 15:03 ` Alan Stern
2011-06-20 16:16 ` Nicolas Pitre
2011-06-20 16:16 ` [PATCH] USB: ehci: use packed, aligned(4) " Nicolas Pitre
2011-06-20 16:48 ` [PATCH] USB: ehci: use packed,aligned(4) " Alan Stern
2011-06-20 16:48 ` Alan Stern
2011-06-20 16:58 ` Arnd Bergmann
2011-06-20 16:58 ` [PATCH] USB: ehci: use packed, aligned(4) " Arnd Bergmann
2011-06-20 19:02 ` Russell King - ARM Linux
2011-06-20 19:02 ` Russell King - ARM Linux
2011-06-20 19:20 ` Nicolas Pitre
2011-06-20 19:20 ` Nicolas Pitre
2011-06-20 19:29 ` Nicolas Pitre
2011-06-20 19:29 ` Nicolas Pitre
2011-06-20 17:10 ` [PATCH] USB: ehci: use packed,aligned(4) " Nicolas Pitre
2011-06-20 17:10 ` [PATCH] USB: ehci: use packed, aligned(4) " Nicolas Pitre
2011-06-20 17:35 ` [PATCH] USB: ehci: use packed,aligned(4) " Alan Stern
2011-06-20 17:35 ` Alan Stern
2011-06-20 18:48 ` Russell King - ARM Linux
2011-06-20 18:48 ` Russell King - ARM Linux
2011-06-20 20:26 ` Arnd Bergmann
2011-06-20 20:26 ` [PATCH] USB: ehci: use packed, aligned(4) " Arnd Bergmann
2011-06-20 20:50 ` Nicolas Pitre
2011-06-20 20:50 ` Nicolas Pitre
2011-06-20 20:55 ` [PATCH] USB: ehci: use packed,aligned(4) " Russell King - ARM Linux
2011-06-20 20:55 ` Russell King - ARM Linux
2011-06-20 21:23 ` Arnd Bergmann
2011-06-20 21:23 ` [PATCH] USB: ehci: use packed, aligned(4) " Arnd Bergmann
2011-06-20 22:23 ` [PATCH] USB: ehci: use packed,aligned(4) " Nicolas Pitre
2011-06-20 22:23 ` [PATCH] USB: ehci: use packed, aligned(4) " Nicolas Pitre
2011-06-21 11:25 ` [PATCH] USB: ehci: use packed,aligned(4) " Arnd Bergmann
2011-06-21 11:25 ` [PATCH] USB: ehci: use packed, aligned(4) " Arnd Bergmann
2011-06-25 1:25 ` Nicolas Pitre
2011-06-25 8:09 ` Arnd Bergmann
2011-06-28 18:51 ` Nicolas Pitre
2011-06-29 10:56 ` Arnd Bergmann
2011-06-20 19:14 ` [PATCH] USB: ehci: use packed,aligned(4) " Nicolas Pitre
2011-06-20 19:14 ` [PATCH] USB: ehci: use packed, aligned(4) " Nicolas Pitre
2011-06-20 19:32 ` Russell King - ARM Linux
2011-06-20 19:32 ` Russell King - ARM Linux
2011-06-20 20:14 ` Arnd Bergmann
2011-06-20 20:14 ` Arnd Bergmann
2011-06-20 20:42 ` [PATCH] USB: ehci: use packed,aligned(4) " Alan Stern
2011-06-20 20:42 ` Alan Stern
2011-06-20 22:36 ` Nicolas Pitre
2011-06-20 22:36 ` [PATCH] USB: ehci: use packed, aligned(4) " Nicolas Pitre
2011-06-21 15:06 ` [PATCH] USB: ehci: use packed,aligned(4) " Alan Stern
2011-06-21 15:06 ` Alan Stern
2011-06-20 17:39 ` Alexander Holler
2011-06-20 17:39 ` Alexander Holler
2011-06-20 18:39 ` Alan Stern
2011-06-20 18:39 ` Alan Stern
2011-06-20 18:46 ` Alexander Holler
2011-06-20 18:46 ` Alexander Holler
2011-06-20 18:57 ` Alan Stern
2011-06-20 18:57 ` Alan Stern
2011-06-20 19:56 ` Nicolas Pitre
2011-06-20 19:56 ` [PATCH] USB: ehci: use packed, aligned(4) " Nicolas Pitre
2011-06-20 21:04 ` [PATCH] USB: ehci: use packed,aligned(4) " Alan Stern
2011-06-20 21:04 ` Alan Stern
2011-06-20 22:31 ` Nicolas Pitre
2011-06-20 22:31 ` [PATCH] USB: ehci: use packed, aligned(4) " Nicolas Pitre
2011-06-21 14:58 ` [PATCH] USB: ehci: use packed,aligned(4) " Alan Stern
2011-06-21 14:58 ` Alan Stern
2011-06-21 20:41 ` Nicolas Pitre
2011-06-21 20:41 ` [PATCH] USB: ehci: use packed, aligned(4) " Nicolas Pitre
2011-06-22 6:23 ` [PATCH] USB: ehci: use packed,aligned(4) " Alexander Holler
2011-06-22 6:23 ` Alexander Holler
2011-06-20 20:09 ` Arnd Bergmann [this message]
2011-06-20 20:09 ` [PATCH] USB: ehci: use packed, aligned(4) " Arnd Bergmann
2011-06-20 21:05 ` [PATCH] USB: ehci: use packed,aligned(4) " Alan Stern
2011-06-20 21:05 ` Alan Stern
2011-06-20 20:07 ` Arnd Bergmann
2011-06-20 20:07 ` [PATCH] USB: ehci: use packed, aligned(4) " Arnd Bergmann
2011-06-20 20:28 ` [PATCH] USB: ehci: use packed,aligned(4) " Nicolas Pitre
2011-06-20 20:28 ` [PATCH] USB: ehci: use packed, aligned(4) " Nicolas Pitre
2011-06-20 20:39 ` Arnd Bergmann
2011-06-20 20:39 ` Arnd Bergmann
2011-06-20 21:03 ` Nicolas Pitre
2011-06-20 21:03 ` Nicolas Pitre
2011-06-23 9:47 ` Alexander Holler
2011-06-23 9:47 ` Alexander Holler
2011-06-23 14:25 ` Alan Stern
2011-06-23 14:25 ` Alan Stern
2011-06-24 11:40 ` Alexander Holler
2011-06-24 11:40 ` Alexander Holler
2011-06-20 16:26 ` [PATCH] USB: ehci: use packed,aligned(4) " Arnd Bergmann
2011-06-20 16:26 ` [PATCH] USB: ehci: use packed, aligned(4) " Arnd Bergmann
2011-06-16 20:30 ` [PATCH] USB: ehci: use packed,aligned(4) " Alan Stern
2011-06-16 20:30 ` Alan Stern
2011-06-16 18:16 ` Alexander Holler
2011-06-16 18:16 ` Alexander Holler
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