From: Dan Dennedy <dan@dennedy.org>
To: Stefan Richter <stefanr@s5r6.in-berlin.de>
Subject: Re: [PATCH] Fix/add raw1394 CONFIG_COMPAT code
Date: Tue, 22 May 2007 21:54:24 -0700
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Cc: Arnd Bergmann <arnd@arndb.de>, Petr Vandrovec <petr@vandrovec.name>,
       linux1394-devel@lists.sourceforge.net, linux-kernel@vger.kernel.org
References: <20070507021447.GA22197@vana.vc.cvut.cz> <200705201703.37561.arnd@arndb.de> <46506912.9020904@s5r6.in-berlin.de>
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On Sunday 20 May 2007 08:28, Stefan Richter wrote:
> Arnd Bergmann wrote:
> > On Sunday 20 May 2007, Stefan Richter wrote:
> >>> Note that this data structure only needs conversion on x86_64 and ia64, 
but
> >>> not on powerpc and other 64 bit architectures that align __u64 also in
> >>> 32 bit mode.
> >> Is this conversion just unnecessary or actually harmful on ppc64 and 
others?
> > 
> > With the current patch, the compat_ioctl function does not handle the 
ppc32
> > version of the structure at all, so it's broken there, it would at least
> > need a 
> > 
> > 	case RAW1394_IOC_GET_CYCLE_TIMER:
> > 		err = raw1394_ioctl(NULL, file, cmd, arg);
> > 		break;
> 
> Dan,
> 
> maybe we should change
> 
> /* argument to RAW1394_IOC_GET_CYCLE_TIMER ioctl */
> struct raw1394_cycle_timer {
> 	/* contents of Isochronous Cycle Timer register,
> 	   as in OHCI 1.1 clause 5.13 (also with non-OHCI hosts) */
> 	__u32 cycle_timer;
> 
> 	/* local time in microseconds since Epoch,
> 	   simultaneously read with cycle timer */
> 	__u64 local_time;
> };
> 
> to
> 
> /* argument to RAW1394_IOC_GET_CYCLE_TIMER ioctl */
> struct raw1394_cycle_timer {
> 	/*
> 	 * least significant 32 bits are contents of Isochronous Cycle
> 	 * Timer register, as in OHCI 1.1 clause 5.13 (also with
> 	 * non-OHCI hosts)
> 	 */
> 	__u64 cycle_timer;
> 
> 	/*
> 	 * local time in microseconds since Epoch,
> 	 * simultaneously read with cycle timer
> 	 */
> 	__u64 local_time;
> };
> 
> before a libraw1394 with get-cycle-timer support is released.
> Shall I prepare according patches for raw1394 and libraw1394?

This seems like a good idea, and I have forwarded it to the ffado (formerly 
freebob) developers, specifically Pieter Palmers--the submitter of 
raw1394_read_cycle_timer--to get his feedback.
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