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2012-03-09T21:09:56.180
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sessyargc.jp's answer was sufficient; however, just for completeness, I wanted to offer a bit of C code that I used to print out some basic tree info from inside the driver: <pre><code>#include <linux/of_device.h> #include <linux/of_platform.h> ... print_device_tree_node(of_find_node_by_path("/"), 0); ... static void print_device_tree_node(struct device_node *node, int depth) { int i = 0; struct device_node *child; struct property *properties; char indent[255] = ""; for(i = 0; i < depth * 3; i++) { indent[i] = ' '; } indent[i] = '\0'; ++depth; for_each_child_of_node(node, child) { printk(KERN_INFO "%s{ name = %s\n", indent, child->name); printk(KERN_INFO "%s type = %s\n", indent, child->type); for (properties = child->properties; properties != NULL; properties = properties->next) { printk(KERN_INFO "%s %s (%d)\n", indent, properties->name, properties->length); } print_device_tree_node(child, depth); printk(KERN_INFO "%s}\n", indent); } } </code></pre> I wish I knew how to determine each properties type, so I could format the value and output it correctly. Any suggestions? Lastly, here is the original snippet, modified oh-so slightly: <pre><code>char *path = "/fpga_dt@c0000000"; struct device_node *dt_node; const u32 *property; int len; dt_node = of_find_node_by_path(path); if (!dt_node) { printk(KERN_ERR "(E) Failed to find device-tree node: %s\n", path); return -ENODEV; } printk(KERN_INFO "(I) Found device-tree node. Now retrieving property.\n"); property = of_get_property(dt_node, "reg", &len); printk(KERN_INFO "(I) len=%d\n", len); printk(KERN_INFO "(I) reg[0]=0x%08lX\n", (unsigned long) property[0]); printk(KERN_INFO "(I) reg[1]=0x%08lX\n", (unsigned long) property[1]); printk(KERN_INFO "(I) reg[2]=0x%08lX\n", (unsigned long) property[2]); printk(KERN_INFO "(I) reg[3]=0x%08lX\n", (unsigned long) property[3]); </code></pre> The seg-fault was happening on some bad device-tree paths. Apparently, there was some typeo error. I ultimately fixed the problem by probing the root path, and then some other basic nodes (like, /cpu0, /memory, etc.), and finally I was able to probe my fpga. I am not sure what really changed, but I am able to reference my FPGA's device-tree node correctly now, when using the above code. Thanks for all the help! :)
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1. POhow to access and debug a FDT/DTS device tree from a Linux driver (seg-fault)
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