The bInterfaceProtocol is hardcoded to USB_CDC_ACM_PROTO_AT_V25TER. This
will lead to problems with ModemManger which will gladly try to probe
that port as a modem if the gadget also has a network function.
ModemManager will try to send AT commands to the ACM port. Make the
bInterfaceProtocol configurable.
This will also set bFunctionProtocol to the same value, see commit
5c8db070b448 ("USB: Change acm_iad_descriptor bFunctionProtocol to
USB_CDC_ACM_PROTO_AT_V25TER") for more details.
Signed-off-by: Michael Walle <mwalle@xxxxxxxxxx>
---
See the following link for the filter logic:
https://gitlab.freedesktop.org/mobile-broadband/ModemManager/-/blob/main/src/mm-filter.c?ref_type=heads#L303
---
.../ABI/testing/configfs-usb-gadget-acm | 7 +++
drivers/usb/gadget/function/f_acm.c | 50 ++++++++++++++++++-
drivers/usb/gadget/function/u_serial.h | 4 ++
3 files changed, 59 insertions(+), 2 deletions(-)
diff --git a/Documentation/ABI/testing/configfs-usb-gadget-acm b/Documentation/ABI/testing/configfs-usb-gadget-acm
index d21092d75a05..25e68be9eb66 100644
--- a/Documentation/ABI/testing/configfs-usb-gadget-acm
+++ b/Documentation/ABI/testing/configfs-usb-gadget-acm
@@ -6,3 +6,10 @@ Description:
This item contains just one readonly attribute: port_num.
It contains the port number of the /dev/ttyGS<n> device
associated with acm function's instance "name".
+
+What: /config/usb-gadget/gadget/functions/acm.name/protocol
+Date: Aug 2024
+KernelVersion: 6.13
+Description:
+ Reported bInterfaceProtocol for the ACM device. For legacy
+ reasons, this defaults to 1 (USB_CDC_ACM_PROTO_AT_V25TER).
diff --git a/drivers/usb/gadget/function/f_acm.c b/drivers/usb/gadget/function/f_acm.c
index 724b2631f249..b78f46586a0f 100644
--- a/drivers/usb/gadget/function/f_acm.c
+++ b/drivers/usb/gadget/function/f_acm.c
@@ -41,6 +41,7 @@ struct f_acm {
struct gserial port;
u8 ctrl_id, data_id;
u8 port_num;
+ u8 bInterfaceProtocol;
u8 pending;
@@ -89,7 +90,7 @@ acm_iad_descriptor = {
.bInterfaceCount = 2, // control + data
.bFunctionClass = USB_CLASS_COMM,
.bFunctionSubClass = USB_CDC_SUBCLASS_ACM,
- .bFunctionProtocol = USB_CDC_ACM_PROTO_AT_V25TER,
+ /* .bFunctionProtocol = DYNAMIC */
/* .iFunction = DYNAMIC */
};
@@ -101,7 +102,7 @@ static struct usb_interface_descriptor acm_control_interface_desc = {
.bNumEndpoints = 1,
.bInterfaceClass = USB_CLASS_COMM,
.bInterfaceSubClass = USB_CDC_SUBCLASS_ACM,
- .bInterfaceProtocol = USB_CDC_ACM_PROTO_AT_V25TER,
+ /* .bInterfaceProtocol = DYNAMIC */
/* .iInterface = DYNAMIC */
};
@@ -663,6 +664,9 @@ acm_bind(struct usb_configuration *c, struct usb_function *f)
goto fail;
acm->notify = ep;
+ acm_iad_descriptor.bFunctionProtocol = acm->bInterfaceProtocol;
+ acm_control_interface_desc.bInterfaceProtocol = acm->bInterfaceProtocol;
+
/* allocate notification */
acm->notify_req = gs_alloc_req(ep,
sizeof(struct usb_cdc_notification) + 2,
@@ -719,8 +723,14 @@ static void acm_unbind(struct usb_configuration *c, struct usb_function *f)
static void acm_free_func(struct usb_function *f)
{
struct f_acm *acm = func_to_acm(f);
+ struct f_serial_opts *opts;
+
+ opts = container_of(f->fi, struct f_serial_opts, func_inst);
kfree(acm);
+ mutex_lock(&opts->lock);
+ opts->refcnt--;
+ mutex_unlock(&opts->lock);
}
static void acm_resume(struct usb_function *f)
@@ -761,7 +771,11 @@ static struct usb_function *acm_alloc_func(struct usb_function_instance *fi)
acm->port.func.disable = acm_disable;
opts = container_of(fi, struct f_serial_opts, func_inst);
+ mutex_lock(&opts->lock);
acm->port_num = opts->port_num;
+ acm->bInterfaceProtocol = opts->protocol;
+ opts->refcnt++;
+ mutex_unlock(&opts->lock);
acm->port.func.unbind = acm_unbind;
acm->port.func.free_func = acm_free_func;
acm->port.func.resume = acm_resume;
@@ -812,11 +826,42 @@ static ssize_t f_acm_port_num_show(struct config_item *item, char *page)
CONFIGFS_ATTR_RO(f_acm_, port_num);
+static ssize_t f_acm_protocol_show(struct config_item *item, char *page)
+{
+ return sprintf(page, "%u\n", to_f_serial_opts(item)->protocol);
+}
+
+static ssize_t f_acm_protocol_store(struct config_item *item,
+ const char *page, size_t count)
+{
+ struct f_serial_opts *opts = to_f_serial_opts(item);
+ int ret;
+
+ mutex_lock(&opts->lock);
+
+ if (opts->refcnt) {
+ ret = -EBUSY;
+ goto out;
+ }
+
+ ret = kstrtou8(page, 0, &opts->protocol);
+ if (ret)
+ goto out;
+ ret = count;
+
+out:
+ mutex_unlock(&opts->lock);
+ return ret;
+}
+
+CONFIGFS_ATTR(f_acm_, protocol);
+
static struct configfs_attribute *acm_attrs[] = {
#ifdef CONFIG_U_SERIAL_CONSOLE
&f_acm_attr_console,
#endif
&f_acm_attr_port_num,
+ &f_acm_attr_protocol,
NULL,
};
@@ -843,6 +888,7 @@ static struct usb_function_instance *acm_alloc_instance(void)
opts = kzalloc(sizeof(*opts), GFP_KERNEL);
if (!opts)
return ERR_PTR(-ENOMEM);
+ opts->protocol = USB_CDC_ACM_PROTO_AT_V25TER;
opts->func_inst.free_func_inst = acm_free_instance;
ret = gserial_alloc_line(&opts->port_num);
if (ret) {
diff --git a/drivers/usb/gadget/function/u_serial.h b/drivers/usb/gadget/function/u_serial.h
index 901d99310bc4..1782d7d7f7be 100644
--- a/drivers/usb/gadget/function/u_serial.h
+++ b/drivers/usb/gadget/function/u_serial.h
@@ -17,6 +17,10 @@
struct f_serial_opts {
struct usb_function_instance func_inst;
u8 port_num;
+ u8 protocol;
+
+ struct mutex lock;
+ int refcnt;
};
/*
--
2.39.2
