Subject: [RFC 0/4] firewire: interface to remote memory (mem1394)
From: Johannes Berg <johannes@sipsolutions.net>
To: linux-kernel@vger.kernel.org
Cc: linux1394-devel@lists.sourceforge.net
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Date: Thu, 02 Feb 2006 23:27:18 +0100
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The following series of four patches adds the possiblity for creating
device nodes for each node attached to the firewire bus and accessing
them (currently read-only) which yields access to the node's RAM, if
supported. This is useful for peeking into machines during debugging
(obviously only if you can attach a firewire cable). This is already
supported via the raw1394 interface, but surfacing this like /dev/mem is
advantageous because then user-space tools can work without
modification.

mem1394 itself is currently a bit limited and lacking on the
error-checking, it will be improved but I wanted to get some comments on
the current patches too. Write support will also be added.

The node interface and dynamic character device allocation are useful on
their own if another layer is ever introduced -- which has been under
discussion once a while to make something similar to raw1394 that gives
access only to certain nodes to separate users.

If you want to test this add a udev rule like the following:
  KERNEL=3D=3D"fwmem-[0-9]*", NAME=3D"fwmem-%s{device/guid}"
and then use
  dd if=3D/dev/fwmem-0x<GUID> bs=3D1K count=3D1024 of=3D/tmp/first-megabyte
to, for example, read the targets first megabyte of memory.

The patches (will be posted as follow-ups):
1/4: node interface
2/4: dynamic cdev allocation below firewire major
3/4: unconditionally export hpsb_send_packet_and_wait
4/4: add mem1394

Comments would be appreciated.

Thanks,
Johannes

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