dmaengine: qcom_hidma: comment platform_driver_register call

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>

diff --git a/drivers/dma/qcom/hidma_mgmt.c b/drivers/dma/qcom/hidma_mgmt.c
index fe87b01f7a4eb1d9c93d1df085a5eb5ec087f32a..62026607f3f8bcff76e2f1cb6d89eefab8a0fd58 100644 (file)
--- a/drivers/dma/qcom/hidma_mgmt.c
+++ b/drivers/dma/qcom/hidma_mgmt.c
@@ -418,6 +418,20 @@ 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;