Re: [Qemu-devel] [RESEND RFC 3/6] device_tree: introduce qemu_fdt_node_path

[Eric Auger <eric.auger@linaro.org>]

On 11/26/2015 01:06 PM, Alex Bennée wrote:
> 
> Eric Auger <eric.auger@linaro.org> writes:
> 
>> This new helper routine returns the node path of a device
>> referred to by its name and compat string.
>>
>> Signed-off-by: Eric Auger <eric.auger@linaro.org>
>> ---
>>  device_tree.c                | 40 ++++++++++++++++++++++++++++++++++++++++
>>  include/sysemu/device_tree.h |  3 +++
>>  2 files changed, 43 insertions(+)
>>
>> diff --git a/device_tree.c b/device_tree.c
>> index 58a5329..f184e3c 100644
>> --- a/device_tree.c
>> +++ b/device_tree.c
>> @@ -171,6 +171,46 @@ static int findnode_nofail(void *fdt, const char *node_path)
>>      return offset;
>>  }
>>
>> +/**
>> + * qemu_fdt_node_path
>> + *
>> + * return the node path of a device, referred to by its node name
>> + * and its compat string
>> + * fdt: pointer to the dt blob
>> + * name: name of the device
>> + * compat: compatibility string of the device
>> + *
>> + * returns the node path
>> + */
>> +int qemu_fdt_node_path(void *fdt, const char *name, char *compat,
>> +                       char **node_path)
>> +{
>> +    int offset = 0, len;
>> +    const char *iter_name;
>> +    char path[256];
>> +    int ret;
>> +
>> +    *node_path = NULL;
>> +    while (1) {
>> +        offset = fdt_node_offset_by_compatible(fdt, offset, compat);
>> +        if (offset == -FDT_ERR_NOTFOUND) {
> 
> Is this not the only error code fdt_node_offset_by_compatible() won't
> return?
> 
>> +            break;
>> +        }
>> +        iter_name = fdt_get_name(fdt, offset, &len);
>> +        if (!strncmp(iter_name, name, len)) {
> 
> is it possible for fdt_get_name to fail here and give you NULL and -len?
I agree with both of your comments. Thanks for spotting my wrong
handling of the errors.

Thank you for your time!

Eric
> 
>> +            goto found;
>> +        }
>> +    }
>> +    return offset;
>> +
>> +found:
>> +    ret = fdt_get_path(fdt, offset, path, 256);
>> +    if (!ret) {
>> +        *node_path = g_strdup(path);
>> +    }
>> +    return ret;
>> +}
>> +
>>  int qemu_fdt_setprop(void *fdt, const char *node_path,
>>                       const char *property, const void *val, int size)
>>  {
>> diff --git a/include/sysemu/device_tree.h b/include/sysemu/device_tree.h
>> index 307e53d..f9e6e6e 100644
>> --- a/include/sysemu/device_tree.h
>> +++ b/include/sysemu/device_tree.h
>> @@ -18,6 +18,9 @@ void *create_device_tree(int *sizep);
>>  void *load_device_tree(const char *filename_path, int *sizep);
>>  void *load_device_tree_from_sysfs(void);
>>
>> +int qemu_fdt_node_path(void *fdt, const char *name, char *compat,
>> +                       char **node_path);
>> +
>>  int qemu_fdt_setprop(void *fdt, const char *node_path,
>>                       const char *property, const void *val, int size);
>>  int qemu_fdt_setprop_cell(void *fdt, const char *node_path,
> 
> 
> --
> Alex Bennée
>