[Xen-devel] [PATCH 2/9] xen: arm: parse modules from DT during early boot.

[Ian Campbell <ian.campbell@xxxxxxxxxx>]

The bootloader should populate /chosen/modules/module@<N>/ for each
module it wishes to pass to the hypervisor. The content of these nodes
is described in docs/misc/arm/device-tree/booting.txt

The hypervisor parses for 2 types of module, linux zImages and linux
initrds. Currently we don't do anything with them.

Signed-off-by: Ian Campbell <ian.campbell@xxxxxxxxxx>
---
v4: Use /chosen/modules/module@N
    Identify module type by compatible property not number.
v3: Use a reg = < > property for the module address/length.
v2: Reserve the zeroeth module for Xen itself (not used yet)
    Use a more idiomatic DT layout
    Document said layout
---
 docs/misc/arm/device-tree/booting.txt |   25 ++++++++++
 xen/common/device_tree.c              |   86 +++++++++++++++++++++++++++++++++
 xen/include/xen/device_tree.h         |   14 +++++
 3 files changed, 125 insertions(+), 0 deletions(-)
 create mode 100644 docs/misc/arm/device-tree/booting.txt

diff --git a/docs/misc/arm/device-tree/booting.txt 
b/docs/misc/arm/device-tree/booting.txt
new file mode 100644
index 0000000..94cd3f1
--- /dev/null
+++ b/docs/misc/arm/device-tree/booting.txt
@@ -0,0 +1,25 @@
+Xen is passed the dom0 kernel and initrd via a reference in the /chosen
+node of the device tree.
+
+Each node has the form /chosen/modules/module@<N> and contains the following
+properties:
+
+- compatible
+
+       Must be:
+
+               "xen,<type>", "xen,multiboot-module"
+
+       where <type> must be one of:
+
+       - "linux-zimage" -- the dom0 kernel
+       - "linux-initrd" -- the dom0 ramdisk
+
+- reg
+
+       Specifies the physical address of the module in RAM and the
+       length of the module.
+
+- bootargs (optional)
+
+       Command line associated with this module
diff --git a/xen/common/device_tree.c b/xen/common/device_tree.c
index da0af77..4bb640e 100644
--- a/xen/common/device_tree.c
+++ b/xen/common/device_tree.c
@@ -270,6 +270,90 @@ static void __init process_cpu_node(const void *fdt, int 
node,
     cpumask_set_cpu(start, &cpu_possible_map);
 }
 
+static int __init process_chosen_modules_node(const void *fdt, int node,
+                                              const char *name, int *depth,
+                                              u32 address_cells, u32 
size_cells)
+{
+    const struct fdt_property *prop;
+    const u32 *cell;
+    int nr, nr_modules = 0;
+    struct dt_mb_module *mod;
+    int len;
+
+    for ( *depth = 1;
+          *depth >= 1;
+          node = fdt_next_node(fdt, node, depth) )
+    {
+        name = fdt_get_name(fdt, node, NULL);
+        if ( strncmp(name, "module@", strlen("module@")) == 0 ) {
+
+            if ( fdt_node_check_compatible(fdt, node,
+                                           "xen,multiboot-module" ) != 0 )
+                early_panic("%s not a compatible module node\n", name);
+
+            if ( fdt_node_check_compatible(fdt, node,
+                                           "xen,linux-zimage") == 0 )
+                nr = 1;
+            else if ( fdt_node_check_compatible(fdt, node,
+                                                "xen,linux-initrd") == 0)
+                nr = 2;
+            else
+                early_panic("%s not a known xen multiboot byte\n");
+
+            if ( nr > nr_modules )
+                nr_modules = nr;
+
+            mod = &early_info.modules.module[nr];
+
+            prop = fdt_get_property(fdt, node, "reg", NULL);
+            if ( !prop )
+                early_panic("node %s missing `reg' property\n", name);
+
+            cell = (const u32 *)prop->data;
+            device_tree_get_reg(&cell, address_cells, size_cells,
+                                &mod->start, &mod->size);
+
+            prop = fdt_get_property(fdt, node, "bootargs", &len);
+            if ( prop )
+            {
+                if ( len > sizeof(mod->cmdline) )
+                    early_panic("module %d command line too long\n", nr);
+
+                safe_strcpy(mod->cmdline, prop->data);
+            }
+            else
+                mod->cmdline[0] = 0;
+        }
+    }
+
+    for ( nr = 1 ; nr < nr_modules ; nr++ )
+    {
+        mod = &early_info.modules.module[nr];
+        if ( !mod->start || !mod->size )
+            early_panic("module %d  missing / invalid\n", nr);
+    }
+
+    early_info.modules.nr_mods = nr_modules;
+    return node;
+}
+
+static void __init process_chosen_node(const void *fdt, int node,
+                                       const char *name,
+                                       u32 address_cells, u32 size_cells)
+{
+    int depth;
+
+    for ( depth = 0;
+          depth >= 0;
+          node = fdt_next_node(fdt, node, &depth) )
+    {
+        name = fdt_get_name(fdt, node, NULL);
+        if ( depth == 1 && strcmp(name, "modules") == 0 )
+            node = process_chosen_modules_node(fdt, node, name, &depth,
+                                               address_cells, size_cells);
+    }
+}
+
 static int __init early_scan_node(const void *fdt,
                                   int node, const char *name, int depth,
                                   u32 address_cells, u32 size_cells,
@@ -279,6 +363,8 @@ static int __init early_scan_node(const void *fdt,
         process_memory_node(fdt, node, name, address_cells, size_cells);
     else if ( device_tree_type_matches(fdt, node, "cpu") )
         process_cpu_node(fdt, node, name, address_cells, size_cells);
+    else if ( device_tree_node_matches(fdt, node, "chosen") )
+        process_chosen_node(fdt, node, name, address_cells, size_cells);
 
     return 0;
 }
diff --git a/xen/include/xen/device_tree.h b/xen/include/xen/device_tree.h
index 4d010c0..c383677 100644
--- a/xen/include/xen/device_tree.h
+++ b/xen/include/xen/device_tree.h
@@ -15,6 +15,7 @@
 #define DEVICE_TREE_MAX_DEPTH 16
 
 #define NR_MEM_BANKS 8
+#define NR_MODULES 2
 
 struct membank {
     paddr_t start;
@@ -26,8 +27,21 @@ struct dt_mem_info {
     struct membank bank[NR_MEM_BANKS];
 };
 
+struct dt_mb_module {
+    paddr_t start;
+    paddr_t size;
+    char cmdline[1024];
+};
+
+struct dt_module_info {
+    int nr_mods;
+    /* Module 0 is Xen itself, followed by the provided modules-proper */
+    struct dt_mb_module module[NR_MODULES + 1];
+};
+
 struct dt_early_info {
     struct dt_mem_info mem;
+    struct dt_module_info modules;
 };
 
 typedef int (*device_tree_node_func)(const void *fdt,
-- 
1.7.9.1


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