All of lore.kernel.org
 help / color / mirror / Atom feed
From: David Laight <David.Laight@ACULAB.COM>
To: 'Mauro Carvalho Chehab' <mchehab@s-opensource.com>,
	Laurent Pinchart <laurent.pinchart@ideasonboard.com>,
	"netdev@vger.kernel.org" <netdev@vger.kernel.org>
Cc: Oliver Neukum <oneukum@suse.com>,
	David Mosberger <davidm@egauge.net>,
	Jaejoong Kim <climbbb.kim@gmail.com>,
	Mauro Carvalho Chehab <mchehab@infradead.org>,
	Mauro Carvalho Chehab <mchehab@kernel.org>,
	"Greg Kroah-Hartman" <gregkh@linuxfoundation.org>,
	"linux-rpi-kernel@lists.infradead.org"
	<linux-rpi-kernel@lists.infradead.org>,
	Jonathan Corbet <corbet@lwn.net>,
	Wolfram Sang <wsa-dev@sang-engineering.com>,
	John Youn <johnyoun@synopsys.com>, Roger Quadros <rogerq@ti.com>,
	"Linux Doc Mailing List" <linux-doc@vger.kernel.org>,
	Linux Media Mailing List <linux-media@vger.kernel.org>,
	"linux-usb@vger.kernel.org" <linux-usb@vger.kernel.org>
Subject: RE: [PATCH 22/22] usb: document that URB transfer_buffer should be aligned
Date: Thu, 30 Mar 2017 11:07:27 +0000	[thread overview]
Message-ID: <063D6719AE5E284EB5DD2968C1650D6DCFFC2476@AcuExch.aculab.com> (raw)
In-Reply-To: <20170330072800.5ee8bc33@vento.lan>

From: Mauro Carvalho Chehab
> Sent: 30 March 2017 11:28
...
> While debugging this issue, I saw *a lot* of network-generated URB
> traffic from RPi3 Ethernet port drivers that were using non-aligned
> buffers and were subject to the temporary buffer conversion.

Buffers from the network stack will almost always be 4n+2 aligned.
Receive data being fed into the network stack really needs to be
4n=2 aligned.

The USB stack almost certainly has to live with that.

If the USB ethernet device doesn't have two bytes of 'pad' before
the frame data (destination MAC address) then you have to solve
the problem within the USB stack.

For transmits it might be possible to send an initial 2 byte fragment
from a separate buffer - but only if arbitrary fragment sizes are
allowed.
A normal USB3 controller should allow this - but you have to be very
careful about what happens at the end of the ring.

	David

  reply	other threads:[~2017-03-30 11:07 UTC|newest]

Thread overview: 53+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2017-03-29 18:54 [PATCH 01/22] driver-api/basics.rst: add device table header Mauro Carvalho Chehab
2017-03-29 18:54 ` [PATCH 02/22] docs-rst: convert usb docbooks to ReST Mauro Carvalho Chehab
2017-03-30  7:48   ` Markus Heiser
2017-03-30  8:21     ` Jani Nikula
2017-03-30  9:20       ` Markus Heiser
2017-03-30 10:12         ` Mauro Carvalho Chehab
2017-03-30 11:17           ` Markus Heiser
2017-03-30 11:35             ` Markus Heiser
2017-03-30 12:10             ` Mauro Carvalho Chehab
2017-03-31 14:46         ` Jonathan Corbet
2017-03-29 18:54 ` [PATCH 03/22] usb.rst: Enrich its ReST representation Mauro Carvalho Chehab
2017-03-29 18:54 ` [PATCH 04/22] gadget.rst: Enrich its ReST representation and add kernel-doc tag Mauro Carvalho Chehab
2017-03-30  7:01   ` Jani Nikula
2017-03-30  7:04     ` Jani Nikula
2017-03-30  9:29       ` Mauro Carvalho Chehab
2017-03-30  8:45     ` Mauro Carvalho Chehab
2017-03-29 18:54 ` [PATCH 05/22] writing_usb_driver.rst: Enrich its ReST representation Mauro Carvalho Chehab
2017-03-29 18:54 ` [PATCH 06/22] writing_musb_glue_layer.rst: " Mauro Carvalho Chehab
2017-03-29 18:54 ` [PATCH 07/22] usb/anchors.txt: convert to ReST and add to driver-api book Mauro Carvalho Chehab
2017-03-29 18:54 ` [PATCH 08/22] usb/bulk-streams.txt: " Mauro Carvalho Chehab
2017-03-29 18:54 ` [PATCH 09/22] usb/callbacks.txt: " Mauro Carvalho Chehab
2017-03-29 18:54 ` [PATCH 10/22] usb/power-management.txt: " Mauro Carvalho Chehab
2017-03-29 18:54 ` [PATCH 11/22] usb/dma.txt: " Mauro Carvalho Chehab
2017-03-29 18:54 ` [PATCH 12/22] error-codes.rst: " Mauro Carvalho Chehab
2017-03-29 18:54 ` [PATCH 13/22] usb/hotplug.txt: " Mauro Carvalho Chehab
2017-03-29 18:54 ` [PATCH 14/22] usb/persist.txt: " Mauro Carvalho Chehab
2017-03-29 18:54 ` [PATCH 15/22] usb/URB.txt: convert to ReST and update it Mauro Carvalho Chehab
2017-03-29 18:54 ` [PATCH 16/22] usb/gadget.rst: remove unused kernel-doc tags Mauro Carvalho Chehab
2017-03-29 18:54 ` [PATCH 17/22] usb.rst: get rid of some Sphinx errors Mauro Carvalho Chehab
2017-03-29 18:54 ` [PATCH 18/22] usb: get rid of some ReST doc build errors Mauro Carvalho Chehab
2017-03-29 18:54 ` [PATCH 19/22] usb: composite.h: fix two warnings when building docs Mauro Carvalho Chehab
2017-03-29 18:54 ` [PATCH 20/22] usb: gadget.h: be consistent at kernel doc macros Mauro Carvalho Chehab
2017-03-29 18:54 ` [PATCH 21/22] docs-rst: fix usb cross-references Mauro Carvalho Chehab
2017-03-29 18:54   ` Mauro Carvalho Chehab
2017-03-29 18:54 ` [PATCH 22/22] usb: document that URB transfer_buffer should be aligned Mauro Carvalho Chehab
2017-03-29 22:15   ` Laurent Pinchart
2017-03-30  1:06     ` Mauro Carvalho Chehab
2017-03-30  9:38       ` Laurent Pinchart
2017-03-30 10:51         ` Mauro Carvalho Chehab
2017-03-30  8:11     ` Oliver Neukum
2017-03-30  9:34       ` Laurent Pinchart
2017-03-30 10:28         ` Mauro Carvalho Chehab
2017-03-30 11:07           ` David Laight [this message]
2017-03-30 12:05           ` Laurent Pinchart
2017-03-30 12:37             ` Mauro Carvalho Chehab
2017-03-30 12:56           ` Oliver Neukum
2017-03-30 14:26             ` Alan Stern
2017-03-30 15:45               ` Mauro Carvalho Chehab
2017-03-30 15:55                 ` Alan Stern
2017-03-30 20:16                   ` Laurent Pinchart
2017-03-30 20:57                   ` Oliver Neukum
2017-03-31 14:07                     ` Alan Stern
2017-03-31  1:26 ` [PATCH 01/22] driver-api/basics.rst: add device table header kbuild test robot

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=063D6719AE5E284EB5DD2968C1650D6DCFFC2476@AcuExch.aculab.com \
    --to=david.laight@aculab.com \
    --cc=climbbb.kim@gmail.com \
    --cc=corbet@lwn.net \
    --cc=davidm@egauge.net \
    --cc=gregkh@linuxfoundation.org \
    --cc=johnyoun@synopsys.com \
    --cc=laurent.pinchart@ideasonboard.com \
    --cc=linux-doc@vger.kernel.org \
    --cc=linux-media@vger.kernel.org \
    --cc=linux-rpi-kernel@lists.infradead.org \
    --cc=linux-usb@vger.kernel.org \
    --cc=mchehab@infradead.org \
    --cc=mchehab@kernel.org \
    --cc=mchehab@s-opensource.com \
    --cc=netdev@vger.kernel.org \
    --cc=oneukum@suse.com \
    --cc=rogerq@ti.com \
    --cc=wsa-dev@sang-engineering.com \
    /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.