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From: David Miller <davem@davemloft.net>
To: mika.westerberg@linux.intel.com
Cc: gregkh@linuxfoundation.org, andreas.noever@gmail.com,
	michael.jamet@intel.com, yehezkel.bernat@intel.com,
	amir.jer.levy@intel.com, Mario.Limonciello@dell.com,
	lukas@wunner.de, andriy.shevchenko@linux.intel.com,
	andrew@lunn.ch, linux-kernel@vger.kernel.org,
	netdev@vger.kernel.org
Subject: Re: [PATCH v2 02/16] thunderbolt: Add support for XDomain properties
Date: Wed, 27 Sep 2017 09:22:16 -0700 (PDT)	[thread overview]
Message-ID: <20170927.092216.1164977518037321262.davem@davemloft.net> (raw)
In-Reply-To: <20170927113241.GB4630@lahna.fi.intel.com>

From: Mika Westerberg <mika.westerberg@linux.intel.com>
Date: Wed, 27 Sep 2017 14:32:41 +0300

> Just for my education, is there some rule which tells when __packed is
> to be used? For example the above structures are all 32-bit aligned but
> how about something like:
> 
> struct foo {
> 	u32 value1;
> 	u8 value2;
> };
> 
> If the on-wire format requires such structures I assume __packed
> is needed here?

Usually header elements are 32-bit aligned in a protocol, so it wouldn't
be specified like that.

The only legitimate case I've seen is where things are purposefully
misaligned within the header, like this:

struct foo {
	u16	x;
	u64	y;
	u16	z;
};

Where the 'y' element is 2-byte aligned.

Fortunately, those situations are extremely rare.

  parent reply	other threads:[~2017-09-27 16:22 UTC|newest]

Thread overview: 28+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2017-09-25 11:07 [PATCH v2 00/16] Thunderbolt networking Mika Westerberg
2017-09-25 11:07 ` [PATCH v2 01/16] byteorder: Move {cpu_to_be32,be32_to_cpu}_array() from Thunderbolt to core Mika Westerberg
2017-09-25 11:07 ` [PATCH v2 02/16] thunderbolt: Add support for XDomain properties Mika Westerberg
2017-09-27  4:33   ` David Miller
2017-09-27 11:32     ` Mika Westerberg
2017-09-27 16:06       ` David Laight
2017-09-27 16:22       ` David Miller [this message]
2017-09-25 11:07 ` [PATCH v2 03/16] thunderbolt: Move enum tb_cfg_pkg_type to thunderbolt.h Mika Westerberg
2017-09-25 11:07 ` [PATCH v2 04/16] thunderbolt: Move thunderbolt domain structure " Mika Westerberg
2017-09-25 11:07 ` [PATCH v2 05/16] thunderbolt: Move tb_switch_phy_port_from_link() " Mika Westerberg
2017-09-25 11:07 ` [PATCH v2 06/16] thunderbolt: Add support for XDomain discovery protocol Mika Westerberg
2017-09-27  4:35   ` David Miller
2017-09-25 11:07 ` [PATCH v2 07/16] thunderbolt: Configure interrupt throttling for all interrupts Mika Westerberg
2017-09-25 11:07 ` [PATCH v2 08/16] thunderbolt: Add support for frame mode Mika Westerberg
2017-09-25 11:07 ` [PATCH v2 09/16] thunderbolt: Export ring handling functions to modules Mika Westerberg
2017-09-25 11:07 ` [PATCH v2 10/16] thunderbolt: Move ring descriptor flags to thunderbolt.h Mika Westerberg
2017-09-25 11:07 ` [PATCH v2 11/16] thunderbolt: Use spinlock in ring serialization Mika Westerberg
2017-09-25 11:07 ` [PATCH v2 12/16] thunderbolt: Use spinlock in NHI serialization Mika Westerberg
2017-09-25 11:07 ` [PATCH v2 13/16] thunderbolt: Add polling mode for rings Mika Westerberg
2017-09-25 11:07 ` [PATCH v2 14/16] thunderbolt: Add function to retrieve DMA device for the ring Mika Westerberg
2017-09-25 11:07 ` [PATCH v2 15/16] thunderbolt: Allocate ring HopID automatically if requested Mika Westerberg
2017-09-25 11:07 ` [PATCH v2 16/16] net: Add support for networking over Thunderbolt cable Mika Westerberg
2017-09-27  4:47   ` David Miller
2017-09-27 13:42     ` Mika Westerberg
2017-09-27 16:27       ` David Miller
2017-09-27 17:27         ` Mika Westerberg
2017-09-27 18:23           ` David Miller
2017-09-26 17:37 ` [PATCH v2 00/16] Thunderbolt networking Andy Shevchenko

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