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From: Alan Stern <stern@rowland.harvard.edu>
To: Alexander Holler <holler@ahsoftware.de>
Cc: Nicolas Pitre <nico@fluxnic.net>, Arnd Bergmann <arnd@arndb.de>,
	<linux-arm-kernel@lists.infradead.org>,
	<linux-usb@vger.kernel.org>, <gregkh@suse.de>,
	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 14:57:29 -0400 (EDT)	[thread overview]
Message-ID: <Pine.LNX.4.44L0.1106201455460.2113-100000@iolanthe.rowland.org> (raw)
In-Reply-To: <4DFF9568.8030704@ahsoftware.de>

On Mon, 20 Jun 2011, Alexander Holler wrote:

> Am 20.06.2011 20:39, schrieb Alan Stern:
> > 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?
> >
> >> 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?
> 
> I don't know. But if there would be no doubts, this discussion would not 
> happen and I assume there never would have been an attribute packed there.

Don't be so sure.  That is very old code; the attribute could easily 
have been present for no good reason.

Alan Stern


WARNING: multiple messages have this Message-ID (diff)
From: stern@rowland.harvard.edu (Alan Stern)
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 14:57:29 -0400 (EDT)	[thread overview]
Message-ID: <Pine.LNX.4.44L0.1106201455460.2113-100000@iolanthe.rowland.org> (raw)
In-Reply-To: <4DFF9568.8030704@ahsoftware.de>

On Mon, 20 Jun 2011, Alexander Holler wrote:

> Am 20.06.2011 20:39, schrieb Alan Stern:
> > 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?
> >
> >> 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?
> 
> I don't know. But if there would be no doubts, this discussion would not 
> happen and I assume there never would have been an attribute packed there.

Don't be so sure.  That is very old code; the attribute could easily 
have been present for no good reason.

Alan Stern

  reply	other threads:[~2011-06-20 18:57 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 [this message]
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
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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