[PATCH] usb: mtu3: Convert to platform remove callback returning void

[PATCH] usb: mtu3: Convert to platform remove callback returning void

[Uwe Kleine-König]

The .remove() callback for a platform driver returns an int which makes
many driver authors wrongly assume it's possible to do error handling by
returning an error code. However the value returned is (mostly) ignored
and this typically results in resource leaks. To improve here there is a
quest to make the remove callback return void. In the first step of this
quest all drivers are converted to .remove_new() which already returns
void.

The function mtu3_remove() can only return a non-zero value if
ssusb->dr_mode is neiter USB_DR_MODE_PERIPHERAL nor USB_DR_MODE_HOST nor
USB_DR_MODE_OTG. In this case however the probe callback doesn't succeed
and so the remove callback isn't called at all. So the code branch
resulting in this error path can just be dropped and then mtu3_remove()
be converted to return void trivially.

Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
---
 drivers/usb/mtu3/mtu3_plat.c | 8 ++------
 1 file changed, 2 insertions(+), 6 deletions(-)

diff --git a/drivers/usb/mtu3/mtu3_plat.c b/drivers/usb/mtu3/mtu3_plat.c
index 6f264b129243..cc53bfa25b23 100644
--- a/drivers/usb/mtu3/mtu3_plat.c
+++ b/drivers/usb/mtu3/mtu3_plat.c
@@ -451,7 +451,7 @@ static int mtu3_probe(struct platform_device *pdev)
 	return ret;
 }
 
-static int mtu3_remove(struct platform_device *pdev)
+static void mtu3_remove(struct platform_device *pdev)
 {
 	struct ssusb_mtk *ssusb = platform_get_drvdata(pdev);
 
@@ -469,8 +469,6 @@ static int mtu3_remove(struct platform_device *pdev)
 		ssusb_gadget_exit(ssusb);
 		ssusb_host_exit(ssusb);
 		break;
-	default:
-		return -EINVAL;
 	}
 
 	ssusb_rscs_exit(ssusb);
@@ -478,8 +476,6 @@ static int mtu3_remove(struct platform_device *pdev)
 	pm_runtime_disable(&pdev->dev);
 	pm_runtime_put_noidle(&pdev->dev);
 	pm_runtime_set_suspended(&pdev->dev);
-
-	return 0;
 }
 
 static int resume_ip_and_ports(struct ssusb_mtk *ssusb, pm_message_t msg)
@@ -615,7 +611,7 @@ MODULE_DEVICE_TABLE(of, mtu3_of_match);
 
 static struct platform_driver mtu3_driver = {
 	.probe = mtu3_probe,
-	.remove = mtu3_remove,
+	.remove_new = mtu3_remove,
 	.driver = {
 		.name = MTU3_DRIVER_NAME,
 		.pm = DEV_PM_OPS,

base-commit: 1c7873e3364570ec89343ff4877e0f27a7b21a61
-- 
2.39.2

Re: [PATCH] usb: mtu3: Convert to platform remove callback returning void

[Greg Kroah-Hartman]

On Sun, Jul 09, 2023 at 06:33:35PM +0200, Uwe Kleine-König wrote:
> The .remove() callback for a platform driver returns an int which makes
> many driver authors wrongly assume it's possible to do error handling by
> returning an error code. However the value returned is (mostly) ignored
> and this typically results in resource leaks. To improve here there is a
> quest to make the remove callback return void. In the first step of this
> quest all drivers are converted to .remove_new() which already returns
> void.
> 
> The function mtu3_remove() can only return a non-zero value if
> ssusb->dr_mode is neiter USB_DR_MODE_PERIPHERAL nor USB_DR_MODE_HOST nor
> USB_DR_MODE_OTG. In this case however the probe callback doesn't succeed
> and so the remove callback isn't called at all. So the code branch
> resulting in this error path can just be dropped and then mtu3_remove()
> be converted to return void trivially.
> 
> Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
> ---
>  drivers/usb/mtu3/mtu3_plat.c | 8 ++------
>  1 file changed, 2 insertions(+), 6 deletions(-)

This patch causes the following build error:

drivers/usb/mtu3/mtu3_plat.c: In function ‘mtu3_remove’:
drivers/usb/mtu3/mtu3_plat.c:460:9: error: enumeration value ‘USB_DR_MODE_UNKNOWN’ not handled in switch [-Werror=switch]
  460 |         switch (ssusb->dr_mode) {
      |         ^~~~~~
cc1: all warnings being treated as errors