From ed054e4e95d6cb0582f1283707ddb40f18d14bfb Mon Sep 17 00:00:00 2001 From: Michael R Sweet Date: Mon, 28 Dec 2020 12:18:24 -0500 Subject: [PATCH] USB: gadget: f_printer: set a default q_len 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 Link: https://lore.kernel.org/r/9DFB1605-63A5-46DB-A5A4-B59B315D8115@msweet.org Signed-off-by: Greg Kroah-Hartman --- 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 64a4112068fc..31eba2a43b1a 100644 --- a/drivers/usb/gadget/function/f_printer.c +++ b/drivers/usb/gadget/function/f_printer.c @@ -51,6 +51,8 @@ #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); @@ -1363,6 +1365,9 @@ 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)) { -- 2.11.0