Hi Wolfram,
On 29.06.2015 11:17, Wolfram Sang wrote:
> On Mon, Jun 29, 2015 at 03:36:19PM +0900, Frkuska, Joshua wrote:
>> This adds of_get_i2c_adapter_by_node which both finds and properly
>> increments the adapter reference count.
>>
>> This is different from of_find_i2c_device_by_node which does not
>> increment the adapter reference counter.
>>
>> Signed-off-by: Vladimir Zapolskiy <vladimir_zapolskiy@xxxxxxxxxx>
>> Signed-off-by: Joshua Frkuska <joshua_frkuska@xxxxxxxxxx>
>
> What is your use case?
the usecase is to avoid double getting of a pointer to the wanted struct
i2c_adapter with incrementing its user counter at once, now it is done
in two stages, namely find adapter and get adapter:
------8<------
struct i2c_adapter *ddc;
int id;
...
- ddc = of_find_i2c_adapter_by_node(ddc_node);
- if (ddc) {
- id = i2c_adapter_id(dcc);
- dcc = i2c_get_adapter(id);
+ dcc = of_get_i2c_adapter_by_node(ddc);
+ if (dcc)
+ put_device(&ddc->dev);
put_device(&ddc->dev);
- }
...
i2c_put_adapter(ddc);
------8<------
Since i2c adapted is locked by client, it might have sense to add
put_device() hidden inside of_get_i2c_adapter_by_node().
> Which code will be using this function?
>
At the moment there is an intention to add clients in drivers/gpu/drm/*,
who should lock i2c bus driver to sustain DDC lines.
By the way to the current version the correspondent change in
include/linux/i2c.h is missing:
------8<------
diff --git a/include/linux/i2c.h b/include/linux/i2c.h
index e83a738..555ad9c 100644
--- a/include/linux/i2c.h
+++ b/include/linux/i2c.h
@@ -638,6 +638,9 @@ extern struct i2c_client
*of_find_i2c_device_by_node(struct device_node *node);
/* must call put_device() when done with returned i2c_adapter device */
extern struct i2c_adapter *of_find_i2c_adapter_by_node(struct
device_node *node);
+/* must call put_device() when done with returned i2c_adapter device */
+extern struct i2c_adapter *of_get_i2c_adapter_by_node(struct
device_node *node);
+
#else
static inline struct i2c_client *of_find_i2c_device_by_node(struct
device_node *node)
@@ -649,6 +652,11 @@ static inline struct i2c_adapter
*of_find_i2c_adapter_by_node(struct device_node
{
return NULL;
}
+
+static inline struct i2c_adapter *of_get_i2c_adapter_by_node(struct
device_node *node)
+{
+ return NULL;
+}
#endif /* CONFIG_OF */
#endif /* _LINUX_I2C_H */
------8<------
--
With best wishes,
Vladimir
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