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USB: gadget: f_printer: set a default q_len

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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@msweet.org>
Link: https://lore.kernel.org/r/9DFB1605-63A5-46DB-A5A4-B59B315D8115@msweet.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Michael R Sweet 2020-12-28 12:18:24 -05:00 committed by Greg Kroah-Hartman
parent 7c9a259846
commit ed054e4e95
1 changed files with 5 additions and 0 deletions
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5
drivers/usb/gadget/function/f_printer.c
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@ -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)) {