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Subject: Re: [PATCH 1/6] GenWQE PCI support, health monitoring and recovery
From: Frank Haverkamp <haver@linux.vnet.ibm.com>
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To: Arnd Bergmann <arnd@arndb.de>
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Organization: IBM
Date: Mon, 09 Dec 2013 13:34:22 +0100
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Hi,

Am Freitag, den 06.12.2013, 09:39 +0100 schrieb Frank Haverkamp:
> Hi Arnd,
> 
> Am Donnerstag, den 05.12.2013, 21:31 +0100 schrieb Arnd Bergmann:
> > On Thursday 05 December 2013, Frank Haverkamp wrote:
> > > > > Was wrong, as already pointed out before. It is now:
> > > > > 
> > > > > struct genwqe_mem {
> > > > >     __u64 addr;
> > > > >     __u64 size;
> > > > >     int direction;
> > > > > };
> > > > > 
> > > > > I hope the int is ok here.
> > > > 
> > > > No, it's not. The problem is that sizeof(struct genwqe_mem) is now 24 on
> > > > most architectures (including x86-64) and 20 on x86-32.
> > > 
> > > Interesting. So int is like long architecture specific. I changed it to
> > > be __u64 too, to avoid any problem.
> > 
> > The solution is ok, but the problem is different from what you thought:
> > 
> > On all architectures that Linux runs on, 'int' is 32 bit. The problem is
> > again the alignment of __u64. On normal architectures, it is naturally
> > aligned, and gcc adds 4 byte padding so that 'sizeof (struct genwqe_mem)'
> > is  multiple of the required alignment. On x86-32, the required alignment
> > for the __u64 members is only 4 bytes, so no padding is added.
> > 
> > 	Arnd

I took some time and converted my test-applications, such that I can
compile them as 32-bit binaries. I had to introduce the
compatibility_ioctl to get the driver working with that. Therefore I
post now my new version v10 which has this change as well.

> now I understand. Interesting. I wondered how one could check this
> automatically such that others don't repeat the mistakes I did.
> 
> I hope I have fixed all those issues now in my latest posting, or do you
> still see some?
> 
> Other than that, is the code ready for inclusion now, or do you still
> like to have other changes done (hopefully not, but if so which ones)?
> 
> Thanks
> 
> Frank


Regards

Frank