Re: [PATCH 04/12] arm: parse modules from DT during early boot.

[Tim Deegan <tim@xen.org>]

At 16:23 +0000 on 13 Nov (1352823796), Ian Campbell wrote:
> The bootloader should populate /chosen/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 allows for 2 modules (@1==kernel and @2==initrd).
> Currently we don't do anything with them.
> 
> Signed-off-by: Ian Campbell <ian.campbell@citrix.com>
> ---
> 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 |   27 ++++++++++++
>  xen/common/device_tree.c              |   75 +++++++++++++++++++++++++++++++++
>  xen/include/xen/device_tree.h         |   14 ++++++
>  3 files changed, 116 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..2609450
> --- /dev/null
> +++ b/docs/misc/arm/device-tree/booting.txt
> @@ -0,0 +1,27 @@
> +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/module@<N> and contains the following
> +properties:
> +
> +- compatible
> +
> +	Must be "xen,multiboot-module"
> +
> +- start
> +
> +	Physical address of the start of this module
> +
> +- end
> +
> +	Physical address of the end of this module
> +
> +- bootargs (optional)
> +
> +	Command line associated with this module
> +
> +The following modules are understood
> +
> +- 1 -- the domain 0 kernel
> +- 2 -- the domain 0 ramdisk
> +
> diff --git a/xen/common/device_tree.c b/xen/common/device_tree.c
> index 3d1f0f4..efd1663 100644
> --- a/xen/common/device_tree.c
> +++ b/xen/common/device_tree.c
> @@ -229,6 +229,79 @@ static void __init process_memory_node(const void *fdt, int node,
>      }
>  }
>  
> +static void __init process_chosen_node(const void *fdt, int node,
> +                                       const char *name,
> +                                       u32 address_cells, u32 size_cells)
> +{
> +    const struct fdt_property *prop;
> +    const u32 *cell;
> +    paddr_t size;
> +    int nr, depth, nr_modules = 0;
> +    struct dt_mb_module *mod;
> +    int len;
> +
> +    for ( depth = 0;
> +          depth >= 0;
> +          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);
> +
> +            nr = simple_strtol(name + strlen("module@"), NULL, 10);
> +            if ( nr <= 0 )
> +                early_panic("Invalid module number %d\n", nr);
> +
> +            if ( nr > NR_MODULES )
> +                early_panic("too many modules %d > %d\n", nr, NR_MODULES);
> +            if ( nr > nr_modules )
> +                nr_modules = nr;
> +
> +            mod = &early_info.modules.module[nr];
> +
> +            prop = fdt_get_property(fdt, node, "start", NULL);
> +            if ( !prop )
> +                early_panic("no start for module %d\n", nr);
> +
> +            cell = (const u32 *)prop->data;
> +            device_tree_get_reg(&cell, address_cells, size_cells,
> +                                &mod->start, &size);

This get_reg returns a start + size -- can/should we encode the module
as one of these rather than encdong start + end separately and
discarding the 'size' fields?

> +
> +            prop = fdt_get_property(fdt, node, "end", NULL);
> +            if ( !prop )
> +                early_panic("no end for module %d\n", nr);
> +
> +            cell = (const u32 *)prop->data;
> +            device_tree_get_reg(&cell, address_cells, size_cells,
> +                                &mod->size, &size);
> +            mod->size -= mod->start;
> +
> +            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;
> +}
> +
>  static int __init early_scan_node(const void *fdt,
>                                    int node, const char *name, int depth,
>                                    u32 address_cells, u32 size_cells,
> @@ -236,6 +309,8 @@ static int __init early_scan_node(const void *fdt,
>  {
>      if ( device_tree_node_matches(fdt, node, "memory") )
>          process_memory_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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