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

[Stefano Stabellini <stefano.stabellini@xxxxxxxxxxxxx>]

On Thu, 6 Dec 2012, Ian Campbell wrote:
> 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;
>  }

You have really written a lot of code here!
I would have thought that just matching on the compatible string would
be enough:

else if ( device_tree_node_matches(fdt, node, "linux-zimage") )
     process_linuxzimage_node(fdt, node, name, address_cells, size_cells);
else if ( device_tree_node_matches(fdt, node, "linux-initrd") )
     process_linuxinitrd_node(fdt, node, name, address_cells, size_cells);

so that your process_linuxzimage_node and process_linuxinitrd_node start
from the right node and have everything they need to parse it



> 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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