* [RFC PATCH 1/1] i2c: core: add of_get_i2c_adapter_by_node
@ 2015-06-29 6:36 Frkuska, Joshua
[not found] ` <5590E763.3090703-nmGgyN9QBj3QT0dZR+AlfA@public.gmane.org>
0 siblings, 1 reply; 3+ messages in thread
From: Frkuska, Joshua @ 2015-06-29 6:36 UTC (permalink / raw)
To: linux-i2c-u79uwXL29TY76Z2rM5mHXA; +Cc: Wolfram Sang
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-nmGgyN9QBj3QT0dZR+AlfA@public.gmane.org>
Signed-off-by: Joshua Frkuska <joshua_frkuska-nmGgyN9QBj3QT0dZR+AlfA@public.gmane.org>
---
drivers/i2c/i2c-core.c | 20 ++++++++++++++++++++
1 file changed, 20 insertions(+)
diff --git a/drivers/i2c/i2c-core.c b/drivers/i2c/i2c-core.c
index 987c124..97caec6 100644
--- a/drivers/i2c/i2c-core.c
+++ b/drivers/i2c/i2c-core.c
@@ -1347,6 +1347,26 @@ struct i2c_adapter
*of_find_i2c_adapter_by_node(struct device_node *node)
return i2c_verify_adapter(dev);
}
EXPORT_SYMBOL(of_find_i2c_adapter_by_node);
+
+/* must call put_device() when done with returned i2c_adapter device */
+struct i2c_adapter *of_get_i2c_adapter_by_node(struct device_node *node)
+{
+ struct device *dev;
+ struct i2c_adapter *adapter;
+
+ dev = bus_find_device(&i2c_bus_type, NULL, node,
+ of_dev_node_match);
+ if (!dev)
+ return NULL;
+
+ adapter = i2c_verify_adapter(dev);
+
+ if (adapter && !try_module_get(adapter->owner))
+ adapter = NULL;
+
+ return adapter;
+}
+EXPORT_SYMBOL(of_get_i2c_adapter_by_node);
#else
static void of_i2c_register_devices(struct i2c_adapter *adap) { }
#endif /* CONFIG_OF */
--
Joshua Frkuska | Embedded Software Engineer
Mentor Embedded Software Division
Mentor Graphics Japan Co., ltd.
^ permalink raw reply related [flat|nested] 3+ messages in thread
* Re: [RFC PATCH 1/1] i2c: core: add of_get_i2c_adapter_by_node
[not found] ` <5590E763.3090703-nmGgyN9QBj3QT0dZR+AlfA@public.gmane.org>
@ 2015-06-29 8:17 ` Wolfram Sang
2015-06-29 14:14 ` Vladimir Zapolskiy
0 siblings, 1 reply; 3+ messages in thread
From: Wolfram Sang @ 2015-06-29 8:17 UTC (permalink / raw)
To: Frkuska, Joshua; +Cc: linux-i2c-u79uwXL29TY76Z2rM5mHXA
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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-nmGgyN9QBj3QT0dZR+AlfA@public.gmane.org>
> Signed-off-by: Joshua Frkuska <joshua_frkuska-nmGgyN9QBj3QT0dZR+AlfA@public.gmane.org>
What is your use case? Which code will be using this function?
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^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: [RFC PATCH 1/1] i2c: core: add of_get_i2c_adapter_by_node
2015-06-29 8:17 ` Wolfram Sang
@ 2015-06-29 14:14 ` Vladimir Zapolskiy
0 siblings, 0 replies; 3+ messages in thread
From: Vladimir Zapolskiy @ 2015-06-29 14:14 UTC (permalink / raw)
To: Wolfram Sang; +Cc: Frkuska, Joshua, linux-i2c-u79uwXL29TY76Z2rM5mHXA
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-nmGgyN9QBj3QT0dZR+AlfA@public.gmane.org>
>> Signed-off-by: Joshua Frkuska <joshua_frkuska-nmGgyN9QBj3QT0dZR+AlfA@public.gmane.org>
>
> 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
^ permalink raw reply related [flat|nested] 3+ messages in thread
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2015-06-29 6:36 [RFC PATCH 1/1] i2c: core: add of_get_i2c_adapter_by_node Frkuska, Joshua
[not found] ` <5590E763.3090703-nmGgyN9QBj3QT0dZR+AlfA@public.gmane.org>
2015-06-29 8:17 ` Wolfram Sang
2015-06-29 14:14 ` Vladimir Zapolskiy
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