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-rw-r--r--Documentation/debugging-via-ohci1394.txt16
1 files changed, 10 insertions, 6 deletions
diff --git a/Documentation/debugging-via-ohci1394.txt b/Documentation/debugging-via-ohci1394.txt
index c360d4e91b48..59a91e5c6909 100644
--- a/Documentation/debugging-via-ohci1394.txt
+++ b/Documentation/debugging-via-ohci1394.txt
@@ -41,15 +41,19 @@ to a working state and enables physical DMA by default for all remote nodes.
41This can be turned off by ohci1394's module parameter phys_dma=0. 41This can be turned off by ohci1394's module parameter phys_dma=0.
42 42
43The alternative firewire-ohci driver in drivers/firewire uses filtered physical 43The alternative firewire-ohci driver in drivers/firewire uses filtered physical
44DMA, hence is not yet suitable for remote debugging. 44DMA by default, which is more secure but not suitable for remote debugging.
45Compile the driver with CONFIG_FIREWIRE_OHCI_REMOTE_DMA (Kernel hacking menu:
46Remote debugging over FireWire with firewire-ohci) to get unfiltered physical
47DMA.
45 48
46Because ohci1394 depends on the PCI enumeration to be completed, an 49Because ohci1394 and firewire-ohci depend on the PCI enumeration to be
47initialization routine which runs pretty early (long before console_init() 50completed, an initialization routine which runs pretty early has been
48which makes the printk buffer appear on the console can be called) was written. 51implemented for x86. This routine runs long before console_init() can be
52called, i.e. before the printk buffer appears on the console.
49 53
50To activate it, enable CONFIG_PROVIDE_OHCI1394_DMA_INIT (Kernel hacking menu: 54To activate it, enable CONFIG_PROVIDE_OHCI1394_DMA_INIT (Kernel hacking menu:
51Provide code for enabling DMA over FireWire early on boot) and pass the 55Remote debugging over FireWire early on boot) and pass the parameter
52parameter "ohci1394_dma=early" to the recompiled kernel on boot. 56"ohci1394_dma=early" to the recompiled kernel on boot.
53 57
54Tools 58Tools
55----- 59-----