From: Lukas Wunner <lukas@xxxxxxxxx>
[ Upstream commit 5e844cc37a5cbaa460e68f9a989d321d63088a89 ]
SPI driver probing currently comprises two steps, whereas removal
comprises only one step:
spi_alloc_master()
spi_register_master()
spi_unregister_master()
That's because spi_unregister_master() calls device_unregister()
instead of device_del(), thereby releasing the reference on the
spi_master which was obtained by spi_alloc_master().
An SPI driver's private data is contained in the same memory allocation
as the spi_master struct. Thus, once spi_unregister_master() has been
called, the private data is inaccessible. But some drivers need to
access it after spi_unregister_master() to perform further teardown
steps.
Introduce devm_spi_alloc_master(), which releases a reference on the
spi_master struct only after the driver has unbound, thereby keeping the
memory allocation accessible. Change spi_unregister_master() to not
release a reference if the spi_master was allocated by the new devm
function.
The present commit is small enough to be backportable to stable.
It allows fixing drivers which use the private data in their ->remove()
hook after it's been freed. It also allows fixing drivers which neglect
to release a reference on the spi_master in the probe error path.
Long-term, most SPI drivers shall be moved over to the devm function
introduced herein. The few that can't shall be changed in a treewide
commit to explicitly release the last reference on the master.
That commit shall amend spi_unregister_master() to no longer release
a reference, thereby completing the migration.
As a result, the behaviour will be less surprising and more consistent
with subsystems such as IIO, which also includes the private data in the
allocation of the generic iio_dev struct, but calls device_del() in
iio_device_unregister().
Signed-off-by: Lukas Wunner <lukas@xxxxxxxxx>
Link: https://lore.kernel.org/r/272bae2ef08abd21388c98e23729886663d19192.1605121038.git.lukas@xxxxxxxxx
Signed-off-by: Mark Brown <broonie@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
drivers/spi/spi.c | 54 +++++++++++++++++++++++++++++++++++++++++++++++-
include/linux/spi/spi.h | 2 +
2 files changed, 55 insertions(+), 1 deletion(-)
--- a/drivers/spi/spi.c
+++ b/drivers/spi/spi.c
@@ -1827,6 +1827,46 @@ struct spi_master *spi_alloc_master(stru
}
EXPORT_SYMBOL_GPL(spi_alloc_master);
+static void devm_spi_release_master(struct device *dev, void *master)
+{
+ spi_master_put(*(struct spi_master **)master);
+}
+
+/**
+ * devm_spi_alloc_master - resource-managed spi_alloc_master()
+ * @dev: physical device of SPI master
+ * @size: how much zeroed driver-private data to allocate
+ * Context: can sleep
+ *
+ * Allocate an SPI master and automatically release a reference on it
+ * when @dev is unbound from its driver. Drivers are thus relieved from
+ * having to call spi_master_put().
+ *
+ * The arguments to this function are identical to spi_alloc_master().
+ *
+ * Return: the SPI master structure on success, else NULL.
+ */
+struct spi_master *devm_spi_alloc_master(struct device *dev, unsigned int size)
+{
+ struct spi_master **ptr, *master;
+
+ ptr = devres_alloc(devm_spi_release_master, sizeof(*ptr),
+ GFP_KERNEL);
+ if (!ptr)
+ return NULL;
+
+ master = spi_alloc_master(dev, size);
+ if (master) {
+ *ptr = master;
+ devres_add(dev, ptr);
+ } else {
+ devres_free(ptr);
+ }
+
+ return master;
+}
+EXPORT_SYMBOL_GPL(devm_spi_alloc_master);
+
#ifdef CONFIG_OF
static int of_spi_register_master(struct spi_master *master)
{
@@ -2007,6 +2047,11 @@ int devm_spi_register_master(struct devi
}
EXPORT_SYMBOL_GPL(devm_spi_register_master);
+static int devm_spi_match_master(struct device *dev, void *res, void *master)
+{
+ return *(struct spi_master **)res == master;
+}
+
static int __unregister(struct device *dev, void *null)
{
spi_unregister_device(to_spi_device(dev));
@@ -2036,7 +2081,14 @@ void spi_unregister_master(struct spi_ma
list_del(&master->list);
mutex_unlock(&board_lock);
- device_unregister(&master->dev);
+ device_del(&master->dev);
+
+ /* Release the last reference on the master if its driver
+ * has not yet been converted to devm_spi_alloc_master().
+ */
+ if (!devres_find(master->dev.parent, devm_spi_release_master,
+ devm_spi_match_master, master))
+ put_device(&master->dev);
}
EXPORT_SYMBOL_GPL(spi_unregister_master);
--- a/include/linux/spi/spi.h
+++ b/include/linux/spi/spi.h
@@ -601,6 +601,8 @@ extern void spi_finalize_current_transfe
/* the spi driver core manages memory for the spi_master classdev */
extern struct spi_master *
spi_alloc_master(struct device *host, unsigned size);
+extern struct spi_master *
+devm_spi_alloc_master(struct device *dev, unsigned int size);
extern int spi_register_master(struct spi_master *master);
extern int devm_spi_register_master(struct device *dev,
