Re: [Qemu-devel] [PATCH v4 4/8] device_tree: qemu_fdt_getprop converted to use the error API

[Peter Crosthwaite]

On Fri, Jan 08, 2016 at 09:32:01AM +, Eric Auger 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 

Reviewed-by: Peter Crosthwaite 

> 
> ---
> 
> 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 
> ---
>  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);
>  if (len != 4) {
>  error_report("%s: %s/%s not 4 bytes long (not a cell?)",
>   __func__, node_path, property);
> 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
> 

[Qemu-devel] [PATCH v4 4/8] device_tree: qemu_fdt_getprop converted to use the error API

[Eric Auger]

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 

---

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 
---
 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);
 if (len != 4) {
 error_report("%s: %s/%s not 4 bytes long (not a cell?)",
  __func__, node_path, property);
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