free address space

QNX Newsgroups (Archives) qdn.public.qnxrtp.embedded
1

Hello,
I use nto on a VME board which is populated with a PCI/VME Bridge (i.e.
Tundra UniverseII ).
I need to map an unused address ( memory and / or PCI ) aera to provide
access to VME through the bridge.
The first solution is to scan memory and PCI to find this free aera. But may
be nto already knows unused space on system.

Any Ideas.
Thanks

2

“Philippe Elskens” <pelskens@tecatom.fr> wrote in
news:a79hk0$7jn$2@inn.qnx.com:

Hello,
I use nto on a VME board which is populated with a PCI/VME Bridge (i.e.
Tundra UniverseII ).
I need to map an unused address ( memory and / or PCI ) aera to provide
access to VME through the bridge.
The first solution is to scan memory and PCI to find this free aera.
But may be nto already knows unused space on system.

You’re looking to find out where you have holes in your physical address
space? Would you already know that from your board specs? I could be mis-
understanding the problem.

\

Cheers,
Adam

QNX Software Systems Ltd.
[ amallory@qnx.com ]

With a PC, I always felt limited by the software available.
On Unix, I am limited only by my knowledge.
–Peter J. Schoenster <pschon@baste.magibox.net>

3

Hello,
I use nto on a VME board which is populated with a PCI/VME Bridge (i.e.
Tundra UniverseII ).
I need to map an unused address ( memory and / or PCI ) aera to provide
access to VME through the bridge.
The first solution is to scan memory and PCI to find this free aera.
But may be nto already knows unused space on system.

You’re looking to find out where you have holes in your physical address
space? Would you already know that from your board specs? I could be
mis-
understanding the problem.

You’re right: I’m looking to find out where are holes in the physical

address space without any considerations about the board specifications.
Philippe

4

“Philippe Elskens” <pelskens@tecatom.fr> wrote in
news:a7cnd0$ijg$1@inn.qnx.com:

You’re right: I’m looking to find out where are holes in the physical
address space without any considerations about the board
specifications. Philippe

I assume you have a well defined behaviour for poking at addresses that
have nothing on the other side.

You could do a write/lagging read of certain boundaries. You write a well
know value (1), write another section w/ well known value (2), read section
(1), verify the well known value is there → assume there is backing store
at that address.

Of course writing willy-nilly to addresses where you don’t know what the
backing store is (ie. flash, some device etc) is really dangerous. Getting
a generic solution at such a low level, for custom/different hardware is
really hard to do.



\

Cheers,
Adam

QNX Software Systems Ltd.
[ amallory@qnx.com ]

With a PC, I always felt limited by the software available.
On Unix, I am limited only by my knowledge.
–Peter J. Schoenster <pschon@baste.magibox.net>

5

Adam Mallory <amallory@qnx.com> wrote in
news:Xns91D95BF1A250amalloryqnxcom@209.226.137.4:

“Philippe Elskens” <> pelskens@tecatom.fr> > wrote in
news:a7cnd0$ijg$> 1@inn.qnx.com> :

You’re right: I’m looking to find out where are holes in the physical
address space without any considerations about the board
specifications. Philippe

I assume you have a well defined behaviour for poking at addresses that
have nothing on the other side.

You could do a write/lagging read of certain boundaries. You write a
well know value (1), write another section w/ well known value (2),
read section (1), verify the well known value is there → assume there
is backing store at that address.

Of course writing willy-nilly to addresses where you don’t know what
the backing store is (ie. flash, some device etc) is really dangerous.
Getting a generic solution at such a low level, for custom/different
hardware is really hard to do.

Just as a follow up, you could also take a look at rsrcdbmgr_attach() to
query the resource database on the layout of the RAM/ROM/devices etc. Of
course your startup code would have had to fill this in properly at boot.

\

Cheers,
Adam

QNX Software Systems Ltd.
[ amallory@qnx.com ]

With a PC, I always felt limited by the software available.
On Unix, I am limited only by my knowledge.
–Peter J. Schoenster <pschon@baste.magibox.net>

6

“Philippe Elskens” <pelskens@tecatom.fr> wrote in message
news:a79hk0$7jn$2@inn.qnx.com…

Hello,
I use nto on a VME board which is populated with a PCI/VME Bridge (i.e.
Tundra UniverseII ).
I need to map an unused address ( memory and / or PCI ) aera to provide
access to VME through the bridge.

So don’t you want to map in the address’s belonging to VME into virtual
memory? In this case you don’t need to scan for free memory?

Are you using pci_attach and other pci_xxxx functions?

The first solution is to scan memory and PCI to find this free aera. But
may
be nto already knows unused space on system.

Any Ideas.
Thanks
\