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

[Julien Grall <julien.grall@xxxxxxxxxx>]

On 05/08/2013 02:18 PM, Ian Campbell wrote:

> 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...


I think yes.

> 
>>  {
>>      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.

I have checked the linux code and the also use strncmp with the length
of "match"/"compatible".

> 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.


This behaviour only happens for the compatible node.

-- 
Julien Grall


_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxx
http://lists.xen.org/xen-devel