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Subject[PATCH v2 9/9] driver core: Add device link flag DL_FLAG_AUTOPROBE_CONSUMER
Date
From: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

Add a new device link flag, DL_FLAG_AUTOPROBE_CONSUMER, to request the
driver core to probe for a consumer driver automatically after binding
a driver to the supplier device on a persistent managed device link.

As unbinding the supplier driver on a managed device link causes the
consumer driver to be detached from its device automatically, this
flag provides a complementary mechanism which is needed to address
some "composite device" use cases.

Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
---
Documentation/driver-api/device_link.rst | 9 +++++++++
drivers/base/core.c | 16 +++++++++++++++-
drivers/base/dd.c | 2 +-
include/linux/device.h | 3 +++
4 files changed, 28 insertions(+), 2 deletions(-)

Index: linux-pm/include/linux/device.h
===================================================================
--- linux-pm.orig/include/linux/device.h
+++ linux-pm/include/linux/device.h
@@ -341,6 +341,7 @@ struct device *driver_find_device(struct
struct device *start, void *data,
int (*match)(struct device *dev, void *data));

+void driver_deferred_probe_add(struct device *dev);
int driver_deferred_probe_check_state(struct device *dev);

/**
@@ -827,12 +828,14 @@ enum device_link_state {
* PM_RUNTIME: If set, the runtime PM framework will use this link.
* RPM_ACTIVE: Run pm_runtime_get_sync() on the supplier during link creation.
* AUTOREMOVE_SUPPLIER: Remove the link automatically on supplier driver unbind.
+ * AUTOPROBE_CONSUMER: Probe consumer driver automatically after supplier binds.
*/
#define DL_FLAG_STATELESS BIT(0)
#define DL_FLAG_AUTOREMOVE_CONSUMER BIT(1)
#define DL_FLAG_PM_RUNTIME BIT(2)
#define DL_FLAG_RPM_ACTIVE BIT(3)
#define DL_FLAG_AUTOREMOVE_SUPPLIER BIT(4)
+#define DL_FLAG_AUTOPROBE_CONSUMER BIT(5)

/**
* struct device_link - Device link representation.
Index: linux-pm/drivers/base/core.c
===================================================================
--- linux-pm.orig/drivers/base/core.c
+++ linux-pm/drivers/base/core.c
@@ -208,6 +208,12 @@ static void device_link_rpm_prepare(stru
* the link will be maintained until one of the devices pointed to by it (either
* the consumer or the supplier) is unregistered.
*
+ * Also, if DL_FLAG_STATELESS, DL_FLAG_AUTOREMOVE_CONSUMER and
+ * DL_FLAG_AUTOREMOVE_SUPPLIER are not set in @flags (that is, a persistent
+ * managed device link is being added), the DL_FLAG_AUTOPROBE_CONSUMER flag can
+ * be used to request the driver core to automaticall probe for a consmer
+ * driver after successfully binding a driver to the supplier device.
+ *
* The combination of DL_FLAG_STATELESS and either DL_FLAG_AUTOREMOVE_CONSUMER
* or DL_FLAG_AUTOREMOVE_SUPPLIER set in @flags at the same time is invalid and
* will cause NULL to be returned upfront.
@@ -228,7 +234,12 @@ struct device_link *device_link_add(stru

if (!consumer || !supplier ||
(flags & DL_FLAG_STATELESS &&
- flags & (DL_FLAG_AUTOREMOVE_CONSUMER | DL_FLAG_AUTOREMOVE_SUPPLIER)))
+ flags & (DL_FLAG_AUTOREMOVE_CONSUMER |
+ DL_FLAG_AUTOREMOVE_SUPPLIER |
+ DL_FLAG_AUTOPROBE_CONSUMER)) ||
+ (flags & DL_FLAG_AUTOPROBE_CONSUMER &&
+ flags & (DL_FLAG_AUTOREMOVE_CONSUMER |
+ DL_FLAG_AUTOREMOVE_SUPPLIER)))
return NULL;

if (flags & DL_FLAG_PM_RUNTIME && flags & DL_FLAG_RPM_ACTIVE) {
@@ -589,6 +600,9 @@ void device_links_driver_bound(struct de

WARN_ON(link->status != DL_STATE_DORMANT);
WRITE_ONCE(link->status, DL_STATE_AVAILABLE);
+
+ if (link->flags & DL_FLAG_AUTOPROBE_CONSUMER)
+ driver_deferred_probe_add(link->consumer);
}

list_for_each_entry(link, &dev->links.suppliers, c_node) {
Index: linux-pm/drivers/base/dd.c
===================================================================
--- linux-pm.orig/drivers/base/dd.c
+++ linux-pm/drivers/base/dd.c
@@ -116,7 +116,7 @@ static void deferred_probe_work_func(str
}
static DECLARE_WORK(deferred_probe_work, deferred_probe_work_func);

-static void driver_deferred_probe_add(struct device *dev)
+void driver_deferred_probe_add(struct device *dev)
{
mutex_lock(&deferred_probe_mutex);
if (list_empty(&dev->p->deferred_probe)) {
Index: linux-pm/Documentation/driver-api/device_link.rst
===================================================================
--- linux-pm.orig/Documentation/driver-api/device_link.rst
+++ linux-pm/Documentation/driver-api/device_link.rst
@@ -94,6 +94,15 @@ Similarly, when the device link is added
``DL_FLAG_AUTOREMOVE_SUPPLIER`` causes the device link to be automatically
purged when the supplier fails to probe or later unbinds.

+If neither ``DL_FLAG_AUTOREMOVE_CONSUMER`` nor ``DL_FLAG_AUTOREMOVE_SUPPLIER``
+is set, ``DL_FLAG_AUTOPROBE_CONSUMER`` can be used to request the driver core
+to probe for a driver for the consumer driver on the link automatically after
+a driver has been bound to the supplier device.
+
+Note, however, that any combinations of ``DL_FLAG_AUTOREMOVE_CONSUMER``,
+``DL_FLAG_AUTOREMOVE_SUPPLIER`` or ``DL_FLAG_AUTOPROBE_CONSUMER`` with
+``DL_FLAG_STATELESS`` are invalid and cannot be used.
+
Limitations
===========

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