1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
|
#include <linux/kernel.h>
#include <linux/init.h>
#include <linux/module.h>
#include <linux/of.h>
MODULE_DESCRIPTION("Kernel module to show off the DeviceTree Kernel API");
MODULE_AUTHOR("Miquel Sabaté Solà");
MODULE_LICENSE("GPL");
MODULE_VERSION("0.0.1");
// `compatible` value for QEMU/KVM.
static const char *const qemu[] = {
"riscv-virtio",
NULL,
};
// `compatible` values that will match on Starfive VisionFive2 v1.3b (plus a
// boogie value).
static const char *const vf2[] = {
"starfive,visionfive-2-v1.3b",
"starfive,jh7110",
"this is bullshit but it won't interfere",
NULL,
};
static int __init dtm_init(void)
{
unsigned int cpu;
struct device_node *node, *parent;
const char *isa;
int rc;
/*
* `of_compatible_match` returns true if there is _one_ element of the given
* array which matches a string on the `compatible` file. That is, not all
* of them have to match.
*/
if (of_machine_compatible_match(qemu)) {
pr_info("Inside of QEMU\n");
} else if (of_machine_compatible_match(vf2)) {
pr_info("Inside of VisionFive2\n");
} else {
pr_info("Somewhere over the rainbow\n");
}
/*
* The `for_each_possible_cpu` is a function-like macro provided by the
* Kernel which allows `cpu` to be an iterator over CPU device nodes.
*/
for_each_possible_cpu(cpu) {
/*
* Given a CPU identifier, `of_cpu_device_node_get` returns a `struct
* device_node` related to the specified CPU (or NULL on error).
*/
node = of_cpu_device_node_get(cpu);
if (!node) {
pr_warn("Unable to find cpu node\n");
continue;
}
/*
* `of_property_present` returns a boolean on whether the given node
* property is present for the given device node.
*/
if (!of_property_present(node, "riscv,isa")) {
pr_warn("Unable to find 'riscv,isa' for this node\n");
goto release_cpu_node;
}
/*
* `of_property_read_string` initializes the given `isa` string with the
* contents of the property we are trying to fetch. Returns 0 on
* success, and a kernel error otherwise. Note that the previous
* `of_property_present` call was actually not needed, we would've get
* here an `-EINVAL` error eitherway.
*/
rc = of_property_read_string(node, "riscv,isa", &isa);
if (rc) {
pr_warn("Unable to find \"riscv,isa\" devicetree entry\n");
goto release_cpu_node;
}
pr_info("RISC-V ISA for '%s': %s\n", node->full_name, isa);
/*
* `of_get_parent` returns the parent device node for the one provided
* or NULL if there's none.
*/
parent = of_get_parent(node);
if (!node) {
pr_warn("No parent for the given node!\n");
goto release_cpu_node;
}
pr_info("parent: %s\n", node->full_name);
/*
* `of_node_put` is used to decrement the reference counter on device
* nodes. We are done using these instances, so we should decrement
* their life times.
*/
of_node_put(parent);
release_cpu_node:
of_node_put(node);
}
return 0;
}
static void __exit dtm_exit(void)
{
pr_info("Exiting from DTM module\n");
}
module_init(dtm_init);
module_exit(dtm_exit);
|
