[PATCH AUTOSEL 5.12 25/63] Revert "dmaengine: qcom_hidma: Check for driver register failure"

[PATCH AUTOSEL 5.12 25/63] Revert "dmaengine: qcom_hidma: Check for driver register failure"

[Sasha Levin]

From: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

[ Upstream commit 43ed0fcf613a87dd0221ec72d1ade4d6544f2ffc ]

This reverts commit a474b3f0428d6b02a538aa10b3c3b722751cb382.

Because of recent interactions with developers from @umn.edu, all
commits from them have been recently re-reviewed to ensure if they were
correct or not.

Upon review, this commit was found to be incorrect for the reasons
below, so it must be reverted.  It will be fixed up "correctly" in a
later kernel change.

The original change is NOT correct, as it does not correctly unwind from
the resources that was allocated before the call to
platform_driver_register().

Cc: Aditya Pakki <pakki001@umn.edu>
Acked-By: Vinod Koul <vkoul@kernel.org>
Acked-By: Sinan Kaya <okaya@kernel.org>
Link: https://lore.kernel.org/r/20210503115736.2104747-51-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 | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/dma/qcom/hidma_mgmt.c b/drivers/dma/qcom/hidma_mgmt.c
index 806ca02c52d7..fe87b01f7a4e 100644
--- a/drivers/dma/qcom/hidma_mgmt.c
+++ b/drivers/dma/qcom/hidma_mgmt.c
@@ -418,8 +418,9 @@ static int __init hidma_mgmt_init(void)
 		hidma_mgmt_of_populate_channels(child);
 	}
 #endif
-	return platform_driver_register(&hidma_mgmt_driver);
+	platform_driver_register(&hidma_mgmt_driver);
 
+	return 0;
 }
 module_init(hidma_mgmt_init);
 MODULE_LICENSE("GPL v2");
-- 
2.30.2

[PATCH AUTOSEL 5.12 26/63] dmaengine: qcom_hidma: comment platform_driver_register call

[Sasha Levin]

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 fe87b01f7a4e..62026607f3f8 100644
--- 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;
-- 
2.30.2