usb: gadget: allocate & giveback serial ports instead hard code them

This patch removes gserial_setup() and gserial_cleanup() and adds
gserial_alloc_line() and gserial_free_line() to replace them.

The initial setup of u_serial happens now on module load time. A
maximum of four TTY ports can be requested which is the current limit.
In theory we could extend this limit, the hard limit is the number of
available endpoints.
alloc_tty_driver() is now called at module init time with the max
available ports. The per-line footprint here is on 32bit is 3 * size of
pointer + 60 bytes (for cdevs).
The remaining memory (struct gs_port) is allocated once a port is
requested.

With this change it is possible to load g_multi and g_serial at the same
time. GS0 receives the module that is loaded first, GS1 is received by
the next module and so on. With the configfs interface the port number
can be exported and the device node is more predictable. Nothing changes
for g_serial and friends as long as one module is used.

Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Felipe Balbi <balbi@ti.com>

1 files changed, 5 insertions, 3 deletions

diff --git a/drivers/usb/gadget/u_serial.h b/drivers/usb/gadget/u_serial.h
index 9b0fe6450fbf..f06ee9a5db51 100644
--- a/drivers/usb/gadget/u_serial.h
+++ b/drivers/usb/gadget/u_serial.h
@@ -15,6 +15,8 @@
 #include <linux/usb/composite.h>
 #include <linux/usb/cdc.h>
 
+#define MAX_U_SERIAL_PORTS	4
+
 /*
  * One non-multiplexed "serial" I/O port ... there can be several of these
  * on any given USB peripheral device, if it provides enough endpoints.
@@ -49,9 +51,9 @@ struct gserial {
 struct usb_request *gs_alloc_req(struct usb_ep *ep, unsigned len, gfp_t flags);
 void gs_free_req(struct usb_ep *, struct usb_request *req);
 
-/* port setup/teardown is handled by gadget driver */
-int gserial_setup(struct usb_gadget *g, unsigned n_ports);
-void gserial_cleanup(void);
+/* management of individual TTY ports */
+int gserial_alloc_line(unsigned char *port_line);
+void gserial_free_line(unsigned char port_line);
 
 /* connect/disconnect is handled by individual functions */
 int gserial_connect(struct gserial *, u8 port_num);