On 07/07/15 13:51, Alessio Igor Bogani wrote:
Current VME stack links windows not to the boards, but to device drivers.
>Driver
>could potentially minimise window usage within it’s scope (any sort of
>window
>reusing, like mapping whole A16 once to be used with all boards), but this
>won’t
>work across multiple drivers. Even if all of your drivers are window-wise
>economic,
>they will still need some amount of windows per each driver. Not that we
>have that
>many kernel drivers...
Yes you can share a window/image between all boards of the same type
(in effect we are porting our drivers in this way)*but* it isn't the
expected way to work (see Documentation/vme_api.txt struct
vme_driver's probe() and match() functions and the GE PIO2 VME
driver).
I think it's perfectly valid to use a single window to dynamically map
to the address space belonging to one of a number of devices supported
by a single driver. I think this is almost preferable to mapping a large
window over a large portion of the VME address space to drive a number
of devices as (depending on there spacing in the VME address space) the
latter could cause issues with filling available PCI address space.
Admittedly this is more of a problem on 32-bit systems, but...
--
Martyn Welch (Lead Software Engineer) | Registered in England and Wales
GE Intelligent Platforms | (3828642) at 100 Barbirolli Square
T +44(0)1327322748 | Manchester, M2 3AB
E martyn.welch@xxxxxx | VAT:GB 927559189
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