netdev - Re: [PATCH net-2.6] can: Fix data length code handling in rx path

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Message-ID: <4B23C602.7050302@grandegger.com>
Date:	Sat, 12 Dec 2009 17:34:10 +0100
From:	Wolfgang Grandegger <wg@...ndegger.com>
To:	Oliver Hartkopp <oliver@...tkopp.net>
CC:	David Miller <davem@...emloft.net>,
	Linux Netdev List <netdev@...r.kernel.org>,
	SocketCAN Core Mailing List <socketcan-core@...ts.berlios.de>
Subject: Re: [PATCH net-2.6] can: Fix data length code handling in rx path

Hi Oliver,

Oliver Hartkopp wrote:
> A valid CAN dataframe can have a data length code (DLC) of 0 .. 8 data bytes.
> 
> When reading the CAN controllers register the 4-bit value may contain values
> from 0 .. 15 which may exceed the reserved space in the socket buffer!
> 
> The ISO 11898-1 Chapter 8.4.2.3 (DLC field) says that register values > 8
> should be reduced to 8 without any error reporting or frame drop.
> 
> This patch introduces a new helper macro to cast a given 4-bit data length
> code (dlc) to __u8 and ensure the DLC value to be max. 8 bytes.
> 
> The different handlings in the rx path of the CAN netdevice drivers are fixed.
> 
> Signed-off-by: Oliver Hartkopp <oliver@...tkopp.net>

Please send you patches inline next time please. For the bfin_can and
the ems_usb driver your patch now masks the dlc with 0xf. Are you sure
this is needed or even correct? Also, s/__u8/u8/, please.

Thanks,

Wolfgang.
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