This commit fixes the way gadget's pullup method (wrapped at
usb_gadget_connect/disconnect) is called in the udc-core.
The composite driver allows correct driver registration, even when it calls
the usb_gadget_disconnect method (composite driver configuration is defered
for user space - please look into the description of usb_composite_probe at
composite.c - line: 1623)
One such example is the CCG (Configurable Composite Gadget) driver (at
drivers/staging/ccg), which after its registration has no usb descriptor
(i.e. idProduct, idVendor etc.) and functions registered. Those are configured
after writing to /sys/module/g_ccg/parameters/ or /sys/class/ccg_usb/ccg0/.
Unfortunately, the code at 'usb_gadget_probe_driver' method (some code omitted):
if (udc_is_newstyle(udc)) {
bind(udc->gadget);
usb_gadget_udc_start(udc->gadget, driver);
usb_gadget_connect(udc->gadget);
}
Explicitly calls the usb_gadget_connect method for this driver. It looks like
the udc-core enables pullup for a driver, which has no functions and no
descriptor filled (those values are feed from userspace).
The USB composite driver API allows correct driver registration with calling
usb_gadget_disconnect method, but as it is now, _ALL_ newstyle usb gadgets are
connected by default. Therefore it violates the composite API.
The solution (at least until the udc-core is reworked) is to add atomic
variable, which helps in balancing the number of called usb_gadget_connect/
disconnect functions.
Signed-off-by: Lukasz Majewski <l.majewski@xxxxxxxxxxx>
Signed-off-by: Kyungmin Park <kyungmin.park@xxxxxxxxxxx>
---
drivers/usb/gadget/udc-core.c | 17 ++++++++++++++++-
include/linux/usb/gadget.h | 13 +++++++++++--
2 files changed, 27 insertions(+), 3 deletions(-)
diff --git a/drivers/usb/gadget/udc-core.c b/drivers/usb/gadget/udc-core.c
index e5e44f8..a26517e 100644
--- a/drivers/usb/gadget/udc-core.c
+++ b/drivers/usb/gadget/udc-core.c
@@ -349,7 +349,22 @@ found:
}
usb_gadget_connect(udc->gadget);
} else {
-
+ /*
+ * This is a hack for "old style" gadgets:
+ *
+ * The udc_start for "old style" gadgets performs implicitly all
+ * operations done by usb_gadget_connect(but not calling it).
+ * Therefore non composite gadgets (like rndis) works even with
+ * wrong connect_count value ("old style" gadgets don't call
+ * usb_gadget_connect/disconnect).
+ *
+ * On the other hand the CCG (Configurable Composite Gadget)
+ * requires this incrementation since it calls
+ * usb_gadget_disconnect on its probe (it is allowed) and hence
+ * the proper balance is needed when the usb_gadget_connect(i.e.
+ * pullup) is called, when triggered from userspace event.
+ */
+ atomic_inc(&udc->gadget->connect_count);
ret = usb_gadget_start(udc->gadget, driver, bind);
if (ret)
goto err1;
diff --git a/include/linux/usb/gadget.h b/include/linux/usb/gadget.h
index 9517466..0801d83 100644
--- a/include/linux/usb/gadget.h
+++ b/include/linux/usb/gadget.h
@@ -534,6 +534,7 @@ struct usb_gadget {
unsigned b_hnp_enable:1;
unsigned a_hnp_support:1;
unsigned a_alt_hnp_support:1;
+ atomic_t connect_count;
const char *name;
struct device dev;
};
@@ -739,7 +740,11 @@ static inline int usb_gadget_connect(struct usb_gadget *gadget)
{
if (!gadget->ops->pullup)
return -EOPNOTSUPP;
- return gadget->ops->pullup(gadget, 1);
+
+ if (atomic_inc_return(&gadget->connect_count) == 1)
+ return gadget->ops->pullup(gadget, 1);
+
+ return 0;
}
/**
@@ -761,7 +766,11 @@ static inline int usb_gadget_disconnect(struct usb_gadget *gadget)
{
if (!gadget->ops->pullup)
return -EOPNOTSUPP;
- return gadget->ops->pullup(gadget, 0);
+
+ if (atomic_dec_and_test(&gadget->connect_count))
+ return gadget->ops->pullup(gadget, 0);
+
+ return 0;
}
--
1.7.2.3
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