Re: [Qemu-devel] [PATCH v2 4/7] device_tree: qemu_fdt_getprop converted to use the error API

[Eric Auger]

Hi Peter,
On 01/07/2016 01:20 AM, Peter Crosthwaite wrote:
> On Wed, Jan 6, 2016 at 7:13 AM, Eric Auger <address@hidden> wrote:
>> Current qemu_fdt_getprop exits if the property is not found. It is
>> sometimes needed to read an optional property, in which case we do
>> not wish to exit but simply returns a null value.
>>
>> This patch converts qemu_fdt_getprop to accept an Error **, and existing
>> users are converted to pass &error_fatal. This preserves the existing
>> behaviour. Then to use the API with your optional semantic a null
>> parameter can be conveyed.
>>
>> Signed-off-by: Eric Auger <address@hidden>
>>
>> ---
>>
>> v1 -> v2:
>> - add a doc comment in the header file
>>
>> RFC -> v1:
>> - get rid of qemu_fdt_getprop_optional and implement Peter's suggestion
>>   that consists in using the error API
>>
>> Signed-off-by: Eric Auger <address@hidden>
>> ---
>>  device_tree.c                | 11 ++++++-----
>>  include/sysemu/device_tree.h | 15 ++++++++++++++-
>>  2 files changed, 20 insertions(+), 6 deletions(-)
>>
>> diff --git a/device_tree.c b/device_tree.c
>> index 8441e01..6ecc9da 100644
>> --- a/device_tree.c
>> +++ b/device_tree.c
>> @@ -321,18 +321,18 @@ int qemu_fdt_setprop_string(void *fdt, const char 
>> *node_path,
>>  }
>>
>>  const void *qemu_fdt_getprop(void *fdt, const char *node_path,
>> -                             const char *property, int *lenp)
>> +                             const char *property, int *lenp, Error **errp)
>>  {
>>      int len;
>>      const void *r;
>> +
>>      if (!lenp) {
>>          lenp = &len;
>>      }
>>      r = fdt_getprop(fdt, findnode_nofail(fdt, node_path), property, lenp);
>>      if (!r) {
>> -        error_report("%s: Couldn't get %s/%s: %s", __func__,
>> -                     node_path, property, fdt_strerror(*lenp));
>> -        exit(1);
>> +        error_setg(errp, "%s: Couldn't get %s/%s: %s", __func__,
>> +                  node_path, property, fdt_strerror(*lenp));
>>      }
>>      return r;
>>  }
>> @@ -341,7 +341,8 @@ uint32_t qemu_fdt_getprop_cell(void *fdt, const char 
>> *node_path,
>>                                 const char *property)
>>  {
>>      int len;
>> -    const uint32_t *p = qemu_fdt_getprop(fdt, node_path, property, &len);
>> +    const uint32_t *p = qemu_fdt_getprop(fdt, node_path, property, &len,
>> +                                         &error_fatal);
> 
> The _cell variant is now inconsistent with the regular _getprop. Can
> we convert them both together and fix the clients to error_fatal?
> (there are only 4 of them).

Yes sure

Best Regards

Eric
> 
> This would become the standard error_propagate pattern.
> 
>>      if (len != 4) {
>>          error_report("%s: %s/%s not 4 bytes long (not a cell?)",
>>                       __func__, node_path, property);
> 
> And this would also convert to error_setg.
> 
> Regards,
> Peter
> 
>> diff --git a/include/sysemu/device_tree.h b/include/sysemu/device_tree.h
>> index 269cb1c..4d7cbb9 100644
>> --- a/include/sysemu/device_tree.h
>> +++ b/include/sysemu/device_tree.h
>> @@ -45,8 +45,21 @@ int qemu_fdt_setprop_string(void *fdt, const char 
>> *node_path,
>>  int qemu_fdt_setprop_phandle(void *fdt, const char *node_path,
>>                               const char *property,
>>                               const char *target_node_path);
>> +/**
>> + * qemu_fdt_getprop: retrieve the value of a given property
>> + * @fdt: pointer to the device tree blob
>> + * @node_path: node path
>> + * @property: name of the property to find
>> + * @lenp: fdt error if any or length of the property on success
>> + * @errp: handle to an error object
>> + *
>> + * returns a pointer to the property on success and NULL on failure
>> + * in case errp is set to &error_fatal, the function auto-asserts
>> + * on error (legacy behavior)
>> + */
>>  const void *qemu_fdt_getprop(void *fdt, const char *node_path,
>> -                             const char *property, int *lenp);
>> +                             const char *property, int *lenp,
>> +                             Error **errp);
>>  uint32_t qemu_fdt_getprop_cell(void *fdt, const char *node_path,
>>                                 const char *property);
>>  uint32_t qemu_fdt_get_phandle(void *fdt, const char *path);
>> --
>> 1.9.1
>>