[PATCH] Fix default q_len for usb_f_printer gadget driver

[PATCH] Fix default q_len for usb_f_printer gadget driver

[Michael R Sweet]

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>
---
 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

Re: [PATCH] Fix default q_len for usb_f_printer gadget driver

[Peter Chen]

On 20-10-30 18:34:19, Michael R Sweet wrote:
> 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>

Reviewed-by: Peter Chen <peter.chen@nxp.com>

Peter
> ---
>  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
> 

-- 

Thanks,
Peter Chen

Re: [PATCH] Fix default q_len for usb_f_printer gadget driver

[Michael Sweet]

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Hi,

I submitted this a month ago, and aside from Peter Chen's "reviewed by" response I haven't heard anything nor seen it get merged.  I know you are all really busy and I don't want to be a pest - is there something else I need to do to advance this patch?

Thanks!


> On Oct 30, 2020, at 6:34 PM, Michael R Sweet <msweet@msweet.org> wrote:
> 
> 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>
> ---
> 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
> 

________________________
Michael Sweet




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[PATCH] Fix default q_len for usb_f_printer gadget driver

[Michael R Sweet]

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>
---
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