Re: [Xen-devel] [PATCH V2 08/33] xen/arm: Add helpers to use the device tree

[Ian Campbell <Ian.Campbell@xxxxxxxxxx>]

On Wed, 2013-05-08 at 03:33 +0100, Julien Grall wrote:
> Signed-off-by: Julien Grall <julien.grall@xxxxxxxxxx>
> 
> Changes in v2:
>     - use dt_node_cmp and dt_compat_cmp in early device tree code
> ---
>  xen/common/device_tree.c      |  127 
> ++++++++++++++++++++++++++++++++++++++++-
>  xen/include/xen/device_tree.h |  120 ++++++++++++++++++++++++++++++++++++++
>  2 files changed, 245 insertions(+), 2 deletions(-)
> 
> diff --git a/xen/common/device_tree.c b/xen/common/device_tree.c
> index bdf8871..449c332 100644
> --- a/xen/common/device_tree.c
> +++ b/xen/common/device_tree.c
> @@ -88,20 +88,23 @@ bool_t device_tree_type_matches(const void *fdt, int 
> node, const char *match)
>      if ( prop == NULL )
>          return 0;
>  
> -    return !strcmp(prop, match);
> +    return !dt_node_cmp(prop, match);
>  }
>  
>  bool_t device_tree_node_compatible(const void *fdt, int node, const char 
> *match)

Aside: I wonder if any of these should be __init...

>  {
>      int len, l;
> +    int mlen;
>      const void *prop;
>  
> +    mlen = strlen(match);
> +
>      prop = fdt_getprop(fdt, node, "compatible", &len);
>      if ( prop == NULL )
>          return 0;
>  
>      while ( len > 0 ) {
> -        if ( !strcmp(prop, match) )
> +        if ( !dt_compat_cmp(prop, match, mlen) )

Is there a change in behaviour here where strlen(match) < strlen(prop)?

I may be mistaken but I think match=="foo" would be compatible with a
node "foobar" now whereas it wasn't before.

On the otherhand this is the same behaviour as dt_device_is_compatible
so maybe it is expected. I seem to recall some name matching code which
explicitly wanted to handle foo@0 as matching foo and things, not sure
that applies here though.

>              return 1;
>          l = strlen(prop) + 1;
>          prop += l;
> @@ -573,6 +576,54 @@ const void *dt_get_property(const struct dt_device_node 
> *np,
>      return pp ? pp->value : NULL;
>  }
>  
> +bool_t dt_device_is_compatible(const struct dt_device_node *device,
> +                               const char *compat)
> +{
> +    const char* cp;
> +    u32 cplen, l;
> +
> +    cp = dt_get_property(device, "compatible", &cplen);
> +    if ( cp == NULL )
> +        return 0;
> +    while ( cplen > 0 )
> +    {
> +        if ( dt_compat_cmp(cp, compat, strlen(compat)) == 0 )
> +            return 1;
> +        l = strlen(cp) + 1;
> +        cp += l;
> +        cplen -= l;
> +    }
> +
> +    return 0;
> +}
> +
> +bool_t dt_machine_is_compatible(const char *compat)
> +{
> +    const struct dt_device_node *root;
> +    bool_t rc = 0;
> +
> +    root = dt_find_node_by_path("/");
> +    if ( root )
> +    {
> +        rc = dt_device_is_compatible(root, compat);
> +    }
> +    return rc;
> +}
> +
> +struct dt_device_node *dt_find_node_by_name(struct dt_device_node *from,
> +                                            const char *name)
> +{
> +    struct dt_device_node *np;
> +    struct dt_device_node *dt;
> +
> +    dt = from ? from->allnext : dt_host;
> +    for_each_device_node(dt, np)
> +        if ( np->name && (dt_node_cmp(np->name, name) == 0) )
> +            break;
> +
> +    return np;
> +}
> +
>  struct dt_device_node *dt_find_node_by_path(const char *path)
>  {
>      struct dt_device_node *np;



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