From: Jeremy Kerr <jk@xxxxxxxxxx>
Once we call fsi_master_unregister, the core will put_device,
potentially freeing the hub master. This change adds a comment
explaining the lifetime of an allocated fsi_master.
We then add a reference from the driver to the hub master, so it stays
around until we've finished ->remove().
Signed-off-by: Jeremy Kerr <jk@xxxxxxxxxx>
Tested-by: Christopher Bostic <cbostic@xxxxxxxxxxxxxxxxxx>
Signed-off-by: Joel Stanley <joel@xxxxxxxxx>
---
drivers/fsi/fsi-master-hub.c | 21 ++++++++++++++++++---
drivers/fsi/fsi-master.h | 15 +++++++++++++++
2 files changed, 33 insertions(+), 3 deletions(-)
diff --git a/drivers/fsi/fsi-master-hub.c b/drivers/fsi/fsi-master-hub.c
index 5e4cd3134bc0..5885fc4a1ef0 100644
--- a/drivers/fsi/fsi-master-hub.c
+++ b/drivers/fsi/fsi-master-hub.c
@@ -288,10 +288,19 @@ static int hub_master_probe(struct device *dev)
hub_master_init(hub);
rc = fsi_master_register(&hub->master);
- if (!rc)
- return 0;
+ if (rc)
+ goto err_release;
+
+ /* At this point, fsi_master_register performs the device_initialize(),
+ * and holds the sole reference on master.dev. This means the device
+ * will be freed (via ->release) during any subsequent call to
+ * fsi_master_unregister. We add our own reference to it here, so we
+ * can perform cleanup (in _remove()) without it being freed before
+ * we're ready.
+ */
+ get_device(&hub->master.dev);
+ return 0;
- kfree(hub);
err_release:
fsi_slave_release_range(fsi_dev->slave, FSI_HUB_LINK_OFFSET,
FSI_HUB_LINK_SIZE * links);
@@ -306,6 +315,12 @@ static int hub_master_remove(struct device *dev)
fsi_slave_release_range(hub->upstream->slave, hub->addr, hub->size);
of_node_put(hub->master.dev.of_node);
+ /*
+ * master.dev will likely be ->release()ed after this, which free()s
+ * the hub
+ */
+ put_device(&hub->master.dev);
+
return 0;
}
diff --git a/drivers/fsi/fsi-master.h b/drivers/fsi/fsi-master.h
index 18bd4ad79356..ee0b46086026 100644
--- a/drivers/fsi/fsi-master.h
+++ b/drivers/fsi/fsi-master.h
@@ -37,6 +37,21 @@ struct fsi_master {
#define dev_to_fsi_master(d) container_of(d, struct fsi_master, dev)
+/**
+ * fsi_master registration & lifetime: the fsi_master_register() and
+ * fsi_master_unregister() functions will take ownership of the master, and
+ * ->dev in particular. The registration path performs a get_device(), which
+ * takes the first reference on the device. Similarly, the unregistration path
+ * performs a put_device(), which may well drop the last reference.
+ *
+ * This means that master implementations *may* need to hold their own
+ * reference (via get_device()) on master->dev. In particular, if the device's
+ * ->release callback frees the fsi_master, then fsi_master_unregister will
+ * invoke this free if no other reference is held.
+ *
+ * The same applies for the error path of fsi_master_register; if the call
+ * fails, dev->release will have been invoked.
+ */
extern int fsi_master_register(struct fsi_master *master);
extern void fsi_master_unregister(struct fsi_master *master);
--
2.15.1
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