From: Alan Stern <stern@rowland.harvard.edu>
To: Nicolas Pitre <nico@fluxnic.net>
Cc: Arnd Bergmann <arnd@arndb.de>,
<linux-arm-kernel@lists.infradead.org>,
Alexander Holler <holler@ahsoftware.de>,
<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: Tue, 21 Jun 2011 11:06:37 -0400 (EDT) [thread overview]
Message-ID: <Pine.LNX.4.44L0.1106211058250.2327-100000@iolanthe.rowland.org> (raw)
In-Reply-To: <alpine.LFD.2.00.1106201653450.2142@xanadu.home>
On Mon, 20 Jun 2011, Nicolas Pitre wrote:
> On Mon, 20 Jun 2011, Alan Stern wrote:
>
> > On Mon, 20 Jun 2011, Nicolas Pitre wrote:
> >
> > > > As far as I can tell, the other structures in ehci.h have
> > > > ((aligned(32)) simply in order to save space, since there can be large
> > > > numbers of these structures allocated.
> > >
> > > How can increasing the alignment to 32 bytes save space?
> >
> > No, no -- the alignment is _decreased_ to 32 bits. Without the
> > attribute the alignment would have been 64 bits.
>
> The aligned attribute requires a byte value not a bit value.
> Maybe what you meant is ((aligned(4)) ?
Ah, very good point! No, I meant ((aligned(32))). Do "grep aligned
drivers/usb/host/ehci.h" and you'll see.
So my understanding was wrong; these structure really are being forced
to a strict alignment. And indeed, now that I go back and look at the
EHCI spec, it turns out that this alignment is required by the
hardware.
Okay, so this digression was irrelevant to our discussion. Forget I
mentioned it...
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: Tue, 21 Jun 2011 11:06:37 -0400 (EDT) [thread overview]
Message-ID: <Pine.LNX.4.44L0.1106211058250.2327-100000@iolanthe.rowland.org> (raw)
In-Reply-To: <alpine.LFD.2.00.1106201653450.2142@xanadu.home>
On Mon, 20 Jun 2011, Nicolas Pitre wrote:
> On Mon, 20 Jun 2011, Alan Stern wrote:
>
> > On Mon, 20 Jun 2011, Nicolas Pitre wrote:
> >
> > > > As far as I can tell, the other structures in ehci.h have
> > > > ((aligned(32)) simply in order to save space, since there can be large
> > > > numbers of these structures allocated.
> > >
> > > How can increasing the alignment to 32 bytes save space?
> >
> > No, no -- the alignment is _decreased_ to 32 bits. Without the
> > attribute the alignment would have been 64 bits.
>
> The aligned attribute requires a byte value not a bit value.
> Maybe what you meant is ((aligned(4)) ?
Ah, very good point! No, I meant ((aligned(32))). Do "grep aligned
drivers/usb/host/ehci.h" and you'll see.
So my understanding was wrong; these structure really are being forced
to a strict alignment. And indeed, now that I go back and look at the
EHCI spec, it turns out that this alignment is required by the
hardware.
Okay, so this digression was irrelevant to our discussion. Forget I
mentioned it...
Alan Stern
next prev parent reply other threads:[~2011-06-21 15:06 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 ` Alan Stern [this message]
2011-06-21 15:06 ` [PATCH] USB: ehci: use packed,aligned(4) " 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
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
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=Pine.LNX.4.44L0.1106211058250.2327-100000@iolanthe.rowland.org \
--to=stern@rowland.harvard.edu \
--cc=arnd@arndb.de \
--cc=gregkh@suse.de \
--cc=holler@ahsoftware.de \
--cc=linux-arm-kernel@lists.infradead.org \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-usb@vger.kernel.org \
--cc=nico@fluxnic.net \
--cc=rabin@rab.in \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.