linux-kernel - [PATCH] Input: break joystick limitation of maximum 80 buttons

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Message-ID: <CACa7zykn0q9XJAUvrqnNATr4DUv3Kc7XujF3vm6sfRB5pE6YNQ@mail.gmail.com>
Date:   Sun, 12 Jul 2020 07:54:54 +0800
From:   Wei Shuai <cpuwolf@...il.com>
To:     "open list:INPUT (KEYBOARD, MOUSE, JOYSTICK, TOUCHSCREEN)..." 
        <linux-input@...r.kernel.org>,
        Dmitry Torokhov <dmitry.torokhov@...il.com>
Cc:     cpuwolf <cpuwolf@...il.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Jeffrey Hugo <jhugo@...eaurora.org>,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>,
        Borislav Petkov <bp@...e.de>, Mattias Jacobsson <2pi@....nu>,
        Mark Gross <mgross@...ux.intel.com>,
        Russell King <rmk+kernel@...linux.org.uk>,
        Erwan Velu <e.velu@...teo.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        open list <linux-kernel@...r.kernel.org>
Subject: [PATCH] Input: break joystick limitation of maximum 80 buttons

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@...il.com>
---
 include/linux/mod_devicetable.h        | 2 +-
 include/uapi/linux/input-event-codes.h | 2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

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)

 /*
--
2.17.1