linux-kernel - Re: [PATCH] uio_pci_generic does not export memory resources

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Message-ID: <20120608151843.GA9705@local>
Date:	Fri, 8 Jun 2012 17:18:43 +0200
From:	"Hans J. Koch" <hjk@...sjkoch.de>
To:	Dominic Eschweiler <eschweiler@...s.uni-frankfurt.de>
Cc:	"Michael S. Tsirkin" <mst@...hat.com>,
	"Hans J. Koch" <hjk@...sjkoch.de>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	kvm@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] uio_pci_generic does not export memory resources

On Fri, Jun 08, 2012 at 04:28:58PM +0200, Dominic Eschweiler wrote:
> Am Freitag, den 08.06.2012, 16:03 +0300 schrieb Michael S. Tsirkin:
> > Why is this needed?
> > What's wrong with mapping resources through
> >  /sys/bus/pci/devices/XXXXXresourceX
> > ?
> > 
> Mmmh ok, the problem here is, that the UIO documentation states:
> 
> "/dev/uioX is used to access the address space of the card. Just use
> mmap() to access registers or RAM locations of your card."
> 
> and
> 
> "From userspace, the different mappings are distinguished by adjusting
> the offset parameter of the mmap() call."
> 
> 
> This does not work and the "/sys/class/uio/uioX/maps/mapX/" directories
> do also not appear.

Then there's something fundamentally wrong in your driver. Check the return
value of uio_register_device().

> I was very confused when I tried UIO the first time
> and it did not behave like it is described in the documentation.

UIO is the mainline since 2007, and I can assure you it works like described.
Lots of people use it.

Try and fix your driver, then post it. If you absolutely don't get it working,
post a non-working version for review.

Thanks,
Hans

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