This allows you to get the equivalent functionality of
i2c_add_numbered_adapter() with all data in the device tree and no
special case code in your driver. This is a common device tree
technique.
For quick reference, the FDT syntax for using an alias to provide an
ID looks like:
aliases {
i2c0 = &i2c_0;
i2c1 = &i2c_1;
};
Signed-off-by: Doug Anderson <dianders@xxxxxxxxxxxx>
Acked-by: Haojian Zhuang <haojian.zhuang@xxxxxxxxx>
---
Changes in v2: None
drivers/i2c/i2c-core.c | 105 +++++++++++++++++++++++++++++++++++-------------
1 files changed, 77 insertions(+), 28 deletions(-)
diff --git a/drivers/i2c/i2c-core.c b/drivers/i2c/i2c-core.c
index e388590..a60ed6d 100644
--- a/drivers/i2c/i2c-core.c
+++ b/drivers/i2c/i2c-core.c
@@ -921,13 +921,81 @@ out_list:
}
/**
+ * i2c_get_number_from_dt - get the adapter number based on dt alias
+ * @adap: the adapter to look at
+ *
+ * Check whether there's an alias in the FDT that gives an ID for this i2c
+ * device. Use an alias like "i2c<nr>", like:
+ * aliases {
+ * i2c0 = &i2c_0;
+ * i2c1 = &i2c_1;
+ * };
+ *
+ * Returns the ID if found. If no alias is found returns -1.
+ */
+static int i2c_get_number_from_dt(struct i2c_adapter *adap)
+{
+ struct device *dev = &adap->dev;
+ int id;
+
+ if (!dev->of_node)
+ return -1;
+
+ id = of_alias_get_id(dev->of_node, "i2c");
+ if (id < 0)
+ return -1;
+ return id;
+}
+
+/**
+ * _i2c_add_numbered_adapter - i2c_add_numbered_adapter where nr is never -1
+ * @adap: the adapter to register (with adap->nr initialized)
+ * Context: can sleep
+ *
+ * See i2c_add_numbered_adapter() for details.
+ */
+static int _i2c_add_numbered_adapter(struct i2c_adapter *adap)
+{
+ int id;
+ int status;
+
+ /* Handled by wrappers */
+ BUG_ON(adap->nr == -1);
+
+ if (adap->nr & ~MAX_IDR_MASK)
+ return -EINVAL;
+
+retry:
+ if (idr_pre_get(&i2c_adapter_idr, GFP_KERNEL) == 0)
+ return -ENOMEM;
+
+ mutex_lock(&core_lock);
+ /* "above" here means "above or equal to", sigh;
+ * we need the "equal to" result to force the result
+ */
+ status = idr_get_new_above(&i2c_adapter_idr, adap, adap->nr, &id);
+ if (status == 0 && id != adap->nr) {
+ status = -EBUSY;
+ idr_remove(&i2c_adapter_idr, id);
+ }
+ mutex_unlock(&core_lock);
+ if (status == -EAGAIN)
+ goto retry;
+
+ if (status == 0)
+ status = i2c_register_adapter(adap);
+ return status;
+}
+
+/**
* i2c_add_adapter - declare i2c adapter, use dynamic bus number
* @adapter: the adapter to add
* Context: can sleep
*
* This routine is used to declare an I2C adapter when its bus number
- * doesn't matter. Examples: for I2C adapters dynamically added by
- * USB links or PCI plugin cards.
+ * doesn't matter or when its bus number is specified by an dt alias.
+ * Examples of bases when the bus number doesn't matter: I2C adapters
+ * dynamically added by USB links or PCI plugin cards.
*
* When this returns zero, a new bus number was allocated and stored
* in adap->nr, and the specified adapter became available for clients.
@@ -937,6 +1005,12 @@ int i2c_add_adapter(struct i2c_adapter *adapter)
{
int id, res = 0;
+ id = i2c_get_number_from_dt(adapter);
+ if (id >= 0) {
+ adapter->nr = id;
+ return _i2c_add_numbered_adapter(adapter);
+ }
+
retry:
if (idr_pre_get(&i2c_adapter_idr, GFP_KERNEL) == 0)
return -ENOMEM;
@@ -983,34 +1057,9 @@ EXPORT_SYMBOL(i2c_add_adapter);
*/
int i2c_add_numbered_adapter(struct i2c_adapter *adap)
{
- int id;
- int status;
-
if (adap->nr == -1) /* -1 means dynamically assign bus id */
return i2c_add_adapter(adap);
- if (adap->nr & ~MAX_IDR_MASK)
- return -EINVAL;
-
-retry:
- if (idr_pre_get(&i2c_adapter_idr, GFP_KERNEL) == 0)
- return -ENOMEM;
-
- mutex_lock(&core_lock);
- /* "above" here means "above or equal to", sigh;
- * we need the "equal to" result to force the result
- */
- status = idr_get_new_above(&i2c_adapter_idr, adap, adap->nr, &id);
- if (status == 0 && id != adap->nr) {
- status = -EBUSY;
- idr_remove(&i2c_adapter_idr, id);
- }
- mutex_unlock(&core_lock);
- if (status == -EAGAIN)
- goto retry;
-
- if (status == 0)
- status = i2c_register_adapter(adap);
- return status;
+ return _i2c_add_numbered_adapter(adap);
}
EXPORT_SYMBOL_GPL(i2c_add_numbered_adapter);
--
1.7.7.3
--
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