usb: gadget: f_acm: Allow restarting ACM console after stopping it

When using IOMUX, the "usbacm" console can be added/removed dynamically
from the stdout/stderr/stdin environment variables to allow temporarily
starting other USB gadgets (e.g. Fastboot).

However, right now acm_stdio_stop() does not completely undo
acm_stdio_start(): The USB gadget is unregistered, but as long as dev->priv
stays set acm_stdio_start() will never register the USB gadget again.

Clear dev->priv after we detach to make sure a start operation after a stop
operation registers the gadget again.

Fixes: fc2b399ac03b ("usb: gadget: Add CDC ACM function")
Signed-off-by: Stephan Gerhold <stephan.gerhold@linaro.org>
Reviewed-by: Mattijs Korpershoek <mkorpershoek@kernel.org>
Link: https://lore.kernel.org/r/20250407-acm-fixes-v1-2-e3dcb592d6d6@linaro.org
Signed-off-by: Mattijs Korpershoek <mkorpershoek@kernel.org>

diff --git a/drivers/usb/gadget/f_acm.c b/drivers/usb/gadget/f_acm.c
index 2665fa4..8f72560 100644 (file)
--- a/drivers/usb/gadget/f_acm.c
+++ b/drivers/usb/gadget/f_acm.c
@@ -663,6 +663,7 @@ static int acm_stdio_stop(struct stdio_dev *dev)
 {
        g_dnl_unregister();
        g_dnl_clear_detach();
+       dev->priv = NULL;
 
        return 0;
 }