[PATCH AUTOSEL 4.14 09/21] dmaengine: qcom_hidma: comment platform_driver_register call

Sasha Levin
2021-05-24T15:13:26Z

From: Phillip Potter <phil@philpotter.co.uk>

[ Upstream commit 4df2a8b0ad634d98a67e540a4e18a60f943e7d9f ]

Place a comment in hidma_mgmt_init explaining why success must
currently be assumed, due to the cleanup issue that would need to
be considered were this module ever to be unloadable or were this
platform_driver_register call ever to fail.

Acked-By: Vinod Koul <vkoul@kernel.org>
Acked-By: Sinan Kaya <okaya@kernel.org>
Signed-off-by: Phillip Potter <phil@philpotter.co.uk>
Link: https://lore.kernel.org/r/20210503115736.2104747-52-gregkh@linuxfoundation.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
drivers/dma/qcom/hidma_mgmt.c | 14 ++++++++++++++
1 file changed, 14 insertions(+)

diff --git a/drivers/dma/qcom/hidma_mgmt.c b/drivers/dma/qcom/hidma_mgmt.c
index 7335e2eb9b72..fd1b3a09de91 100644
--- a/drivers/dma/qcom/hidma_mgmt.c
+++ b/drivers/dma/qcom/hidma_mgmt.c
@@ -454,6 +454,20 @@ static int __init hidma_mgmt_init(void)
hidma_mgmt_of_populate_channels(child);
}
#endif
+ /*
+ * We do not check for return value here, as it is assumed that
+ * platform_driver_register must not fail. The reason for this is that
+ * the (potential) hidma_mgmt_of_populate_channels calls above are not
+ * cleaned up if it does fail, and to do this work is quite
+ * complicated. In particular, various calls of of_address_to_resource,
+ * of_irq_to_resource, platform_device_register_full, of_dma_configure,
+ * and of_msi_configure which then call other functions and so on, must
+ * be cleaned up - this is not a trivial exercise.
+ *
+ * Currently, this module is not intended to be unloaded, and there is
+ * no module_exit function defined which does the needed cleanup. For
+ * this reason, we have to assume success here.
+ */
platform_driver_register(&hidma_mgmt_driver);

return 0;
--
2.30.2