diff mbox series

Input: break joystick limitation of maximum 80 buttons

Message ID CACa7zykn0q9XJAUvrqnNATr4DUv3Kc7XujF3vm6sfRB5pE6YNQ@mail.gmail.com
State New
Headers show
Series Input: break joystick limitation of maximum 80 buttons | expand

Commit Message

Wei Shuai July 11, 2020, 11:54 p.m. UTC
The joystick max buttons 80 limitation comes from

#define BTN_JOYSTICK 0x120
#define BTN_DEAD 0x12f
#define BTN_TRIGGER_HAPPY 0x2c0
#define KEY_MAX 0x2ff

include/uapi/linux/input-event-codes.h

according to function hidinput_configure_usage() in file drivers/hid/hid-input.c

the joystick button mapping is not a continues space
generally speaking, the mapping space is from

1. BTN_JOYSTICK~BTN_DEAD
2. BTN_TRIGGER_HAPPY~KEY_MAX

Finally, I got the max limitation is 80.
The patch is expanding KEY_MAX from 0x2ff to 4ff
and the change has been verified on 104 button USB HID device on Ubuntu

Signed-off-by: Wei Shuai <cpuwolf@gmail.com>
---
 include/linux/mod_devicetable.h        | 2 +-
 include/uapi/linux/input-event-codes.h | 2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

--
2.17.1

Comments

Andy Shevchenko July 13, 2020, 9:06 a.m. UTC | #1
On Sun, Jul 12, 2020 at 07:54:54AM +0800, Wei Shuai wrote:
> The joystick max buttons 80 limitation comes from
> 
> #define BTN_JOYSTICK 0x120
> #define BTN_DEAD 0x12f
> #define BTN_TRIGGER_HAPPY 0x2c0
> #define KEY_MAX 0x2ff
> 
> include/uapi/linux/input-event-codes.h
> 
> according to function hidinput_configure_usage() in file drivers/hid/hid-input.c
> 
> the joystick button mapping is not a continues space
> generally speaking, the mapping space is from
> 
> 1. BTN_JOYSTICK~BTN_DEAD
> 2. BTN_TRIGGER_HAPPY~KEY_MAX
> 
> Finally, I got the max limitation is 80.
> The patch is expanding KEY_MAX from 0x2ff to 4ff
> and the change has been verified on 104 button USB HID device on Ubuntu


If you send and resend this patch too often, nobody will take you seriously.
Also, you have to provide versioning and changelog in each submission.
Besides that, above doesn't answer to question "why?". Why are you doing this
at all? What the problem?
Wei Shuai July 13, 2020, 10:29 a.m. UTC | #2
hi Andy,
sorry from a newbie

we found Linux kernel has max joystick buttons up to 80, no more

We are selling USB joystick device QMCP737C for flight simulator,
which is nothing but common USB joystick. it has 104 buttons

Product link
https://x-plane.vip/quickmade/qmcp737c/

it works well on Windows, Mac, but not on Linux.
Linux kernel exposes /dev/input/js0 max to 80 button, but we have 104 buttons.

I did a lot of google search, but nothing I got. then I have to look
at Kernel source, to find out where this number max 80 comes from

Eventually, I found the final limitation

#define BTN_JOYSTICK 0x120
#define BTN_DEAD 0x12f
#define BTN_TRIGGER_HAPPY 0x2c0
#define KEY_MAX 0x2ff

include/uapi/linux/input-event-codes.h

according to function hidinput_configure_usage() in file drivers/hid/hid-input.c

the joystick button mapping is not a continues space, generally speak
the mapping space is from

BTN_JOYSTICK~BTN_DEAD
BTN_TRIGGER_HAPPY~KEY_MAX

and finally, I got the max limitation is 80.

my question is why KEY_MAX is 0x2ff?  this number 0x2ff looks like not
align with char? integer? the answer is no

so may I ask to expand KEY_MAX to such as 0x4ff?

Andy Shevchenko <andriy.shevchenko@linux.intel.com> 于2020年7月13日周一 下午5:06写道:
>
> On Sun, Jul 12, 2020 at 07:54:54AM +0800, Wei Shuai wrote:
> > The joystick max buttons 80 limitation comes from
> >
> > #define BTN_JOYSTICK 0x120
> > #define BTN_DEAD 0x12f
> > #define BTN_TRIGGER_HAPPY 0x2c0
> > #define KEY_MAX 0x2ff
> >
> > include/uapi/linux/input-event-codes.h
> >
> > according to function hidinput_configure_usage() in file drivers/hid/hid-input.c
> >
> > the joystick button mapping is not a continues space
> > generally speaking, the mapping space is from
> >
> > 1. BTN_JOYSTICK~BTN_DEAD
> > 2. BTN_TRIGGER_HAPPY~KEY_MAX
> >
> > Finally, I got the max limitation is 80.
> > The patch is expanding KEY_MAX from 0x2ff to 4ff
> > and the change has been verified on 104 button USB HID device on Ubuntu
>
>
> If you send and resend this patch too often, nobody will take you seriously.
> Also, you have to provide versioning and changelog in each submission.
> Besides that, above doesn't answer to question "why?". Why are you doing this
> at all? What the problem?
>
>
> --
> With Best Regards,
> Andy Shevchenko
>
>
diff mbox series

Patch

diff --git a/include/linux/mod_devicetable.h b/include/linux/mod_devicetable.h
index 8d764aab29de..35eb59ae1f19 100644
--- a/include/linux/mod_devicetable.h
+++ b/include/linux/mod_devicetable.h
@@ -311,7 +311,7 @@  struct pcmcia_device_id {
 /* Input */
 #define INPUT_DEVICE_ID_EV_MAX         0x1f
 #define INPUT_DEVICE_ID_KEY_MIN_INTERESTING    0x71
-#define INPUT_DEVICE_ID_KEY_MAX                0x2ff
+#define INPUT_DEVICE_ID_KEY_MAX                0x4ff
 #define INPUT_DEVICE_ID_REL_MAX                0x0f
 #define INPUT_DEVICE_ID_ABS_MAX                0x3f
 #define INPUT_DEVICE_ID_MSC_MAX                0x07
diff --git a/include/uapi/linux/input-event-codes.h
b/include/uapi/linux/input-event-codes.h
index b6a835d37826..ad1b9bed3828 100644
--- a/include/uapi/linux/input-event-codes.h
+++ b/include/uapi/linux/input-event-codes.h
@@ -774,7 +774,7 @@ 

 /* We avoid low common keys in module aliases so they don't get huge. */
 #define KEY_MIN_INTERESTING    KEY_MUTE
-#define KEY_MAX                        0x2ff
+#define KEY_MAX                        0x4ff
 #define KEY_CNT                        (KEY_MAX+1)

 /*