Re: UIO: missing resource mapping

["Michael S. Tsirkin" <mst@redhat.com>]

On Fri, Jul 13, 2012 at 04:42:51PM +0200, Dominic Eschweiler wrote:
> Am Freitag, den 13.07.2012, 16:22 +0300 schrieb Michael S. Tsirkin:
> > Could you give an example of the problem? How do you bind
> > both UIO and another driver to the same device? 
> 
> Sorry, I'm looking on it from the user-space perspective. Maybe I'm
> wrong, but I can give you an example :
> 
> lspci -v
> ...
> 03:00.0 Network controller: Broadcom Corporation BCM4331 802.11a/b/g/n
> (rev 02)
> 	Subsystem: Apple Inc. AirPort Extreme
> 	Flags: bus master, fast devsel, latency 0, IRQ 17
> 	Memory at b0600000 (64-bit, non-prefetchable) [size=16K]
> 	Capabilities: [40] Power Management version 3
> 	Capabilities: [58] Vendor Specific Information: Len=78 <?>
> 	Capabilities: [48] MSI: Enable- Count=1/1 Maskable- 64bit+
> 	Capabilities: [d0] Express Endpoint, MSI 00
> 	Capabilities: [100] Advanced Error Reporting
> 	Capabilities: [13c] Virtual Channel
> 	Capabilities: [160] Device Serial Number 85-f2-6d-ff-ff-42-68-a8
> 	Capabilities: [16c] Power Budgeting <?>
> 	Kernel driver in use: bcma-pci-bridge
> ...
> 
> This Device has one 64 Bit Bar. When I look at the related sysfs
> entry ...
> 
> 
> ls /sys/bus/pci/devices/0000:03:00.0
> ...
> --w------- 1 root root 4.0K Jul 13 16:35 reset
> -r--r--r-- 1 root root 4.0K Jul 12 21:43 resource
> -rw------- 1 root root  16K Jul 13 16:35 resource0
> lrwxrwxrwx 1 root root    0 Jul 12 23:41 subsystem
> -> ../../../../bus/pci
> ...
> 
> ... I can see that it should be possible to map resource0 and directly
> write into a BAR which is already managed by a kernel drivers. 
> 
> Moving this functionality to UIO would only generate those resource
> files, if the device is handled by UIO and therefore intended to be
> managed from the user-space. 

UIO has the same property, doesn't it? Multiple users can
access device memory through sysfs.


> -- 
> Gruß
>   Dominic