In some cases a driver may want to monitor multiple cables on a single
extcon. For example a charger driver will typically want to monitor all
of EXTCON_CHG_USB_SDP, EXTCON_CHG_USB_CDP, EXTCON_CHG_USB_DCP to configure
the max. current it can sink while charging.
Due to the signature of the notifier_call function + how extcon passes
state and the extcon_dev as parameters this requires using one
notifier_block + one notifier_call function per cable, otherwise the
notifier_call function cannot get to its driver's data (using container_of
requires it to know which notifier block its first parameter is).
For a driver wanting to monitor the above 3 cables that would result
in something like this:
static const unsigned int vbus_cable_ids[] = {
EXTCON_CHG_USB_SDP, EXTCON_CHG_USB_CDP, EXTCON_CHG_USB_DCP };
struct driver_data {
struct notifier_block vbus_nb[ARRAY_SIZE(vbus_cable_ids)];
}
/*
* We need 3 copies of this, because there is no way to find out for which
* cable id we are being called from the passed in arguments; and we must
* have a separate nb for each extcon_register_notifier call.
*/
static int vbus_cable0_evt(struct notifier_block *nb, unsigned long e, void *p)
{
struct driver_data *data =
container_of(nb, struct driver_data, vbus_nb[0]);
...
}
static int vbus_cable1_evt(struct notifier_block *nb, unsigned long e, void *p)
{
struct driver_data *data =
container_of(nb, struct driver_data, vbus_nb[1]);
...
}
static int vbus_cable2_evt(struct notifier_block *nb, unsigned long e, void *p)
{
struct driver_data *data =
container_of(nb, struct driver_data, vbus_nb[2]);
...
}
int probe(...)
{
/* Register for vbus notification */
data->vbus_nb[0].notifier_call = vbus_cable0_evt;
data->vbus_nb[1].notifier_call = vbus_cable1_evt;
data->vbus_nb[2].notifier_call = vbus_cable2_evt;
for (i = 0; i < ARRAY_SIZE(vbus_cable_ids); i++) {
ret = devm_extcon_register_notifier(dev, data->vbus_extcon,
vbus_cable_ids[i], &data->vbus_nb[i]);
if (ret)
...
}
}
And then in the event handling the driver often checks the state of
all cables explicitly using extcon_get_state, rather then using the
event argument to the notifier_call.
This commit makes extcon_[un]register_notifier accept -1 as cable-id,
which will cause the notifier to get called for changes on any cable
on the extcon_dev. Compared to the above example code this allows much
simpler code in drivers which want to monitor multiple cable types.
Signed-off-by: Hans de Goede <hdego...@redhat.com>
---
Changes in v2:
-Fix false-positive "warning: 'idx' may be used uninitialized" warning
seen with some compiler versions
---
drivers/extcon/extcon.c | 35 ++++++++++++++++++++++++++---------
drivers/extcon/extcon.h | 1 +
2 files changed, 27 insertions(+), 9 deletions(-)
diff --git a/drivers/extcon/extcon.c b/drivers/extcon/extcon.c
index 09ac5e7..2a042ee 100644
--- a/drivers/extcon/extcon.c
+++ b/drivers/extcon/extcon.c
@@ -449,6 +449,7 @@ int extcon_sync(struct extcon_dev *edev, unsigned int id)
state = !!(edev->state & BIT(index));
raw_notifier_call_chain(&edev->nh[index], state, edev);
+ raw_notifier_call_chain(&edev->nh_all, 0, edev);
/* This could be in interrupt handler */
prop_buf = (char *)get_zeroed_page(GFP_ATOMIC);
@@ -900,6 +901,8 @@ EXPORT_SYMBOL_GPL(extcon_get_extcon_dev);
* any attach status changes from the extcon.
* @edev: the extcon device that has the external connecotr.
* @id: the unique id of each external connector in extcon
enumeration.
+ * or -1 to get notififications for all cables on edev, in this
+ * case no state info will get passed to the notifier_call.
* @nb: a notifier block to be registered.
*
* Note that the second parameter given to the callback of nb (val) is
@@ -915,12 +918,18 @@ int extcon_register_notifier(struct extcon_dev *edev,
unsigned int id,
if (!edev || !nb)
return -EINVAL;
- idx = find_cable_index_by_id(edev, id);
- if (idx < 0)
- return idx;
+ if ((int)id != -1) {
+ idx = find_cable_index_by_id(edev, id);
+ if (idx < 0)
+ return idx;
+ }
spin_lock_irqsave(&edev->lock, flags);
- ret = raw_notifier_chain_register(&edev->nh[idx], nb);
+ if ((int)id != -1)
+ ret = raw_notifier_chain_register(&edev->nh[idx], nb);
+ else
+ ret = raw_notifier_chain_register(&edev->nh_all, nb);
+
spin_unlock_irqrestore(&edev->lock, flags);
return ret;
@@ -937,17 +946,23 @@ int extcon_unregister_notifier(struct extcon_dev *edev,
unsigned int id,
struct notifier_block *nb)
{
unsigned long flags;
- int ret, idx;
+ int ret, idx = 0;
if (!edev || !nb)
return -EINVAL;
- idx = find_cable_index_by_id(edev, id);
- if (idx < 0)
- return idx;
+ if ((int)id != -1) {
+ idx = find_cable_index_by_id(edev, id);
+ if (idx < 0)
+ return idx;
+ }
spin_lock_irqsave(&edev->lock, flags);
- ret = raw_notifier_chain_unregister(&edev->nh[idx], nb);
+ if ((int)id != -1)
+ ret = raw_notifier_chain_unregister(&edev->nh[idx], nb);
+ else
+ ret = raw_notifier_chain_unregister(&edev->nh_all, nb);
+
spin_unlock_irqrestore(&edev->lock, flags);
return ret;
@@ -1212,6 +1227,8 @@ int extcon_dev_register(struct extcon_dev *edev)
for (index = 0; index < edev->max_supported; index++)
RAW_INIT_NOTIFIER_HEAD(&edev->nh[index]);
+ RAW_INIT_NOTIFIER_HEAD(&edev->nh_all);
+
dev_set_drvdata(&edev->dev, edev);
edev->state = 0;
diff --git a/drivers/extcon/extcon.h b/drivers/extcon/extcon.h
index 993ddcc..2e6c09d 100644
--- a/drivers/extcon/extcon.h
+++ b/drivers/extcon/extcon.h
@@ -44,6 +44,7 @@ struct extcon_dev {
/* Internal data. Please do not set. */
struct device dev;
struct raw_notifier_head *nh;
+ struct raw_notifier_head nh_all;
struct list_head entry;
int max_supported;
spinlock_t lock; /* could be called by irq handler */
--
2.9.3
