usb: gadget: configfs: allow setting function instance's name

USB function's configfs config group is created in a generic way in
usb/gadget/configfs.c:function_make(), which in turn delegates actual
allocation and setup of the USB function instance to a particular
implementation, e.g. in f_acm.c. The said implementation does its job
in a parameter-less function e.g. acm_alloc_instance(), which results
in creating an unnamed config group, whose name is set later in
function_make(). function_make() creates the name by parsing a string
of the form:

<function name>.<instance name>

which comes from userspace as a parameter to mkdir invocation.

Up to now only <function name> has been used, while <instance name>
has been ignored. This patch adds a set_inst_name() operation to
struct usb_function_instance which allows passing the <instance name>
from function_make() so that it is not ignored. It is entirely up to the
implementor of set_inst_name() what to do with the <instance name>.

In a typical case, the struct usb_function_instance is embedded in a
larger struct which is retrieved in set_inst_name() with container_of(),
and the larger struct contains a field to store the <instance name>.

Signed-off-by: Andrzej Pietrasiewicz <andrzej.p@samsung.com>
Signed-off-by: Kyungmin Park <kyungmin.park@samsung.com>
Acked-by: Michal Nazarewicz <mina86@mina86.com>
Signed-off-by: Felipe Balbi <balbi@ti.com>

1 files changed, 7 insertions, 0 deletions

diff --git a/drivers/usb/gadget/configfs.c b/drivers/usb/gadget/configfs.c
index 25885112fa35..d6c8ab4a5327 100644
--- a/drivers/usb/gadget/configfs.c
+++ b/drivers/usb/gadget/configfs.c
@@ -564,6 +564,13 @@ static struct config_group *function_make(
 		usb_put_function_instance(fi);
 		return ERR_PTR(ret);
 	}
+	if (fi->set_inst_name) {
+		ret = fi->set_inst_name(fi, instance_name);
+		if (ret) {
+			usb_put_function_instance(fi);
+			return ERR_PTR(ret);
+		}
+	}
 
 	gi = container_of(group, struct gadget_info, functions_group);