The usb_f_printer gadget driver uses a default q_len value of *0* which prevents
any IO from occurring. Moreover, once the driver is instantiated it is
impossible to change the q_len value.
The following patch uses a default q_len value of 10 which matches the legacy
g_printer gadget driver. This minimizes the possibility that you end up with a
non-working printer gadget. It is still possible to set the q_len to a
different value using the configfs path of the same name.
Signed-off-by: Michael R Sweet <msweet@xxxxxxxxxx>
---
drivers/usb/gadget/function/f_printer.c | 5 +++++
1 file changed, 5 insertions(+)
diff --git a/drivers/usb/gadget/function/f_printer.c b/drivers/usb/gadget/function/f_printer.c
index 9c7ed2539ff7..4f3161005e4f 100644
--- a/drivers/usb/gadget/function/f_printer.c
+++ b/drivers/usb/gadget/function/f_printer.c
@@ -50,6 +50,8 @@
#define GET_PORT_STATUS 1
#define SOFT_RESET 2
+#define DEFAULT_Q_LEN 10 /* same as legacy g_printer gadget */
+
static int major, minors;
static struct class *usb_gadget_class;
static DEFINE_IDA(printer_ida);
@@ -1317,6 +1319,9 @@ static struct usb_function_instance *gprinter_alloc_inst(void)
opts->func_inst.free_func_inst = gprinter_free_inst;
ret = &opts->func_inst;
+ /* Make sure q_len is initialized, otherwise the bound device can't support read/write! */
+ opts->q_len = DEFAULT_Q_LEN;
+
mutex_lock(&printer_ida_lock);
if (ida_is_empty(&printer_ida)) {
--
2.17.1
