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Subject[PATCH v1 2/5] driver core: Allow a device to wait on optional suppliers
From
Before this change, if a device is waiting on suppliers, it's assumed
that all those suppliers are needed for the device to probe
successfully. This change allows marking a devices as waiting only on
optional suppliers. This allows a device to wait on suppliers (and link
to them as soon as they are available) without preventing the device
from being probed.

Signed-off-by: Saravana Kannan <saravanak@google.com>
---
drivers/base/core.c | 28 +++++++++++++++++++++++++---
include/linux/device.h | 3 +++
2 files changed, 28 insertions(+), 3 deletions(-)

diff --git a/drivers/base/core.c b/drivers/base/core.c
index 17ed054c4132..48cd43a91ce6 100644
--- a/drivers/base/core.c
+++ b/drivers/base/core.c
@@ -480,13 +480,25 @@ EXPORT_SYMBOL_GPL(device_link_add);
* This function is NOT meant to be called from the probe function of the
* consumer but rather from code that creates/adds the consumer device.
*/
-static void device_link_wait_for_supplier(struct device *consumer)
+static void device_link_wait_for_supplier(struct device *consumer,
+ bool need_for_probe)
{
mutex_lock(&wfs_lock);
list_add_tail(&consumer->links.needs_suppliers, &wait_for_suppliers);
+ consumer->links.need_for_probe = need_for_probe;
mutex_unlock(&wfs_lock);
}

+static void device_link_wait_for_mandatory_supplier(struct device *consumer)
+{
+ device_link_wait_for_supplier(consumer, true);
+}
+
+static void device_link_wait_for_optional_supplier(struct device *consumer)
+{
+ device_link_wait_for_supplier(consumer, false);
+}
+
/**
* device_link_add_missing_supplier_links - Add links from consumer devices to
* supplier devices, leaving any
@@ -656,7 +668,8 @@ int device_links_check_suppliers(struct device *dev)
* probe.
*/
mutex_lock(&wfs_lock);
- if (!list_empty(&dev->links.needs_suppliers)) {
+ if (!list_empty(&dev->links.needs_suppliers) &&
+ dev->links.need_for_probe) {
mutex_unlock(&wfs_lock);
return -EPROBE_DEFER;
}
@@ -760,6 +773,15 @@ void device_links_driver_bound(struct device *dev)
{
struct device_link *link;

+ /*
+ * If a device probes successfully, it's expected to have created all
+ * the device links it needs to or make new device links as it needs
+ * them. So, it no longer needs to wait on any suppliers.
+ */
+ mutex_lock(&wfs_lock);
+ list_del_init(&dev->links.needs_suppliers);
+ mutex_unlock(&wfs_lock);
+
device_links_write_lock();

list_for_each_entry(link, &dev->links.consumers, s_node) {
@@ -2393,7 +2415,7 @@ int device_add(struct device *dev)

if (fwnode_has_op(dev->fwnode, add_links)
&& fwnode_call_int_op(dev->fwnode, add_links, dev))
- device_link_wait_for_supplier(dev);
+ device_link_wait_for_mandatory_supplier(dev, true);

bus_probe_device(dev);
if (parent)
diff --git a/include/linux/device.h b/include/linux/device.h
index f1f2aa0b19da..4fd33da9a848 100644
--- a/include/linux/device.h
+++ b/include/linux/device.h
@@ -1156,6 +1156,8 @@ enum dl_dev_state {
* @consumers: List of links to consumer devices.
* @needs_suppliers: Hook to global list of devices waiting for suppliers.
* @defer_sync: Hook to global list of devices that have deferred sync_state.
+ * @need_for_probe: If needs_suppliers is on a list, this indicates if the
+ * suppliers are needed for probe or not.
* @status: Driver status information.
*/
struct dev_links_info {
@@ -1163,6 +1165,7 @@ struct dev_links_info {
struct list_head consumers;
struct list_head needs_suppliers;
struct list_head defer_sync;
+ bool need_for_probe;
enum dl_dev_state status;
};

--
2.24.0.rc0.303.g954a862665-goog
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