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Subject[PATCH v6 6/7] usb: gadget: legacy/serial: allow dynamic removal
Legacy serial USB gadget is still useful as an early console,
before userspace is up. Later it could be replaced with proper
configfs-configured composite gadget - that use case is enabled
by this patch.

Signed-off-by: Michał Mirosław <mirq-linux@rere.qmqm.pl>

---
v6: rebased on balbi/testing/next
v5: no changes
v4: initial revision, new in the patchset

---
drivers/usb/gadget/legacy/serial.c | 49 +++++++++++++++++++++++++++++-
1 file changed, 48 insertions(+), 1 deletion(-)

diff --git a/drivers/usb/gadget/legacy/serial.c b/drivers/usb/gadget/legacy/serial.c
index de30d7628eef..da44f89f5e73 100644
--- a/drivers/usb/gadget/legacy/serial.c
+++ b/drivers/usb/gadget/legacy/serial.c
@@ -97,6 +97,36 @@ static unsigned n_ports = 1;
module_param(n_ports, uint, 0);
MODULE_PARM_DESC(n_ports, "number of ports to create, default=1");

+static bool enable = true;
+
+static int switch_gserial_enable(bool do_enable);
+
+static int enable_set(const char *s, const struct kernel_param *kp)
+{
+ bool do_enable;
+ int ret;
+
+ if (!s) /* called for no-arg enable == default */
+ return 0;
+
+ ret = strtobool(s, &do_enable);
+ if (ret || enable == do_enable)
+ return ret;
+
+ ret = switch_gserial_enable(do_enable);
+ if (!ret)
+ enable = do_enable;
+
+ return ret;
+}
+
+static const struct kernel_param_ops enable_ops = {
+ .set = enable_set,
+ .get = param_get_bool,
+};
+
+module_param_cb(enable, &enable_ops, &enable, 0644);
+
/*-------------------------------------------------------------------------*/

static struct usb_configuration serial_config_driver = {
@@ -240,6 +270,19 @@ static struct usb_composite_driver gserial_driver = {
.unbind = gs_unbind,
};

+static int switch_gserial_enable(bool do_enable)
+{
+ if (!serial_config_driver.label)
+ /* init() was not called, yet */
+ return 0;
+
+ if (do_enable)
+ return usb_composite_probe(&gserial_driver);
+
+ usb_composite_unregister(&gserial_driver);
+ return 0;
+}
+
static int __init init(void)
{
/* We *could* export two configs; that'd be much cleaner...
@@ -266,12 +309,16 @@ static int __init init(void)
}
strings_dev[STRING_DESCRIPTION_IDX].s = serial_config_driver.label;

+ if (!enable)
+ return 0;
+
return usb_composite_probe(&gserial_driver);
}
module_init(init);

static void __exit cleanup(void)
{
- usb_composite_unregister(&gserial_driver);
+ if (enable)
+ usb_composite_unregister(&gserial_driver);
}
module_exit(cleanup);
--
2.20.1
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