Re: [Xen-devel] [PATCH 06/16] arm: parse modules from DT during early boot.

[Stefano Stabellini <stefano.stabellini@xxxxxxxxxxxxx>]

On Mon, 3 Sep 2012, Ian Campbell wrote:
> The bootloader should populate /chosen/nr-modules with the number of
> modules and then for each module 0..nr-modules-1 it should populate
> /chosen/moduleN-{start,end} with the physical address of the module.

Considering that we can traverse the DT and enumerate all the children
of a particular node, we don't need a nr-modules property.

Also I would rather move all the modules under /chosen/modules than have
/chosen/module-N.

We could even go as far as having one single modules node, with every
module expressed as a reg range in memory.

Then you can document that for Xen the first module should be the linux
kernel and the second module should be the initrd.

chosen {
    modules {
        reg = < first_address first_size >, <second_address second_size>;
    };
};

Besides being more concise and requiring simpler parsing, I think that
it is much more... aesthetic :)


> The hypervisor allows for 2 modules (kernel and initrd). Currently we
> don't do anything with them.
> 
> Signed-off-by: Ian Campbell <ian.campbell@xxxxxxxxxx>
> ---
>  xen/common/device_tree.c      |   57 
> +++++++++++++++++++++++++++++++++++++++++
>  xen/include/xen/device_tree.h |    7 +++++
>  2 files changed, 64 insertions(+), 0 deletions(-)
> 
> diff --git a/xen/common/device_tree.c b/xen/common/device_tree.c
> index 3d1f0f4..226e3f3 100644
> --- a/xen/common/device_tree.c
> +++ b/xen/common/device_tree.c
> @@ -229,6 +229,61 @@ 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 i, nr_modules;
> +
> +    prop = fdt_get_property(fdt, node, "nr-modules", NULL);
> +    if ( !prop )
> +    {
> +        early_info.modules.nr_mods = 0;
> +        return;
> +    }
> +
> +    cell = (const u32 *)prop->data;
> +    get_val(&cell, 1, (u64*)&nr_modules);
> +
> +    if ( nr_modules > NR_MODULES )
> +    {
> +        early_panic("too many modules %d > %d\n", nr_modules, NR_MODULES);
> +    }
> +
> +    for ( i = 0; i < nr_modules; i++ )
> +    {
> +        struct membank *mod = &early_info.modules.module[i];
> +        /* longest prop name is "start", single digit numbers of modules */
> +        char propname[strlen("moduleX-start") + 1];
> +
> +        BUILD_BUG_ON(NR_MODULES > 9);
> +
> +        snprintf(propname, sizeof(propname), "module%d-start", i+1);
> +        prop = fdt_get_property(fdt, node, propname, NULL);
> +        if ( !prop )
> +            early_panic("no start for module %d\n", i);
> +
> +        cell = (const u32 *)prop->data;
> +        device_tree_get_reg(&cell, address_cells, size_cells,
> +                            &mod->start, &size);

I don't think you should be using device_tree_get_reg to parse a non reg
property


> +        snprintf(propname, sizeof(propname), "module%d-end", i+1);
> +        prop = fdt_get_property(fdt, node, propname, NULL);
> +        if ( !prop )
> +            early_panic("no end for module %d\n", i);
> +
> +        cell = (const u32 *)prop->data;
> +        device_tree_get_reg(&cell, address_cells, size_cells,
> +                            &mod->size, &size);
> +        mod->size -= mod->start;
> +    }
> +
> +    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 +291,8 @@ 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..585fcc9 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 +27,14 @@ struct dt_mem_info {
>      struct membank bank[NR_MEM_BANKS];
>  };
>  
> +struct dt_module_info {
> +    int nr_mods;
> +    struct membank module[NR_MODULES];
> +};
> +
>  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
> 
> 
> _______________________________________________
> Xen-devel mailing list
> Xen-devel@xxxxxxxxxxxxx
> http://lists.xen.org/xen-devel
> 

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