Re: [PATCH v3] Fix modifier keys for Redragon Asura Keyboard

[Benjamin Tissoires]

Hi Robert,

First, apologies for not answering to the RFC. I missed it and it fell
down in my INBOX.

On Wed, Mar 21, 2018 at 11:43 AM, Robert Munteanu <rombert@xxxxxxxxxx> wrote:
> The microdia family of keyboards uses a non-standard way of sending
> modifier keys.
>
> The down event always sets the first bit to 0x04 and the second keycode

Pretty sure you are talking about bytes here, not bits.
And in the HID world, the first byte is usually a report ID.

> to a custom value For instance, left shift sends the following bits
>
>   04 02 00 00 00 00 00 00
>
> while left control sends
>
>   04 01 00 00 00 00 00 00

This sounds like bit(0) is mapped to LEFT_SHIFT and bit(1) mapped to
LEFT_CONTROL in the second byte.
Fortunately, LeftControl is designed in HID as 0xe0 in the keyboard
HID usage table, and LeftShift is 0xe1. So that would match the
behavior you are seeing.
If you have 04 04 00 00 00 00 00 00 when pressing LeftAlt, then
definitively you are just facing a bitmask, which is fairly common.

>
> As a result all modifier keys are mapped to left shift and the keyboard is
> non-functional in that respect. To solve the problem, we capture the
> raw data in raw_event and manually generate the correct input events.

I'd like to see the hid-recorder events from these keypresses. The
device might be buggy, but I have a gut feeling your solution is not
the simplest one.
Please grab hid-recorder from http://bentiss.github.io/hid-replay-docs/

>
> The keyboard functions mostly as expected now, with only a few minor
> issues:
>
> - two USB devices are detected instead of 1

Well, that should be easy enough to solve

> - some key combinations are not triggered - e.g.
>   left shift + left ctrl + p. However, the same combination is recognized
>   with the right shift key.

Could you add this combination in the hid-recorder output too?

more comments inlined:

>
> Changelog:
>
> - v2: modifier keys work, some combinations are still troublesome
> - v3: style cleanup, rebase on top of 4.14
> - v4: remove most debugging calls, make init info useful for user,
>   rebased on top of 4.15
>
> Signed-off-by: Robert Munteanu <rombert@xxxxxxxxxx>
> ---
>  drivers/hid/Kconfig        |   9 +++
>  drivers/hid/Makefile       |   2 +-
>  drivers/hid/hid-core.c     |   3 +
>  drivers/hid/hid-ids.h      |   3 +
>  drivers/hid/hid-microdia.c | 148 +++++++++++++++++++++++++++++++++++++++++++++
>  5 files changed, 164 insertions(+), 1 deletion(-)
>  create mode 100644 drivers/hid/hid-microdia.c
>
> diff --git a/drivers/hid/Kconfig b/drivers/hid/Kconfig
> index 779c5ae47f36..c3350f2ec4ea 100644
> --- a/drivers/hid/Kconfig
> +++ b/drivers/hid/Kconfig
> @@ -548,6 +548,15 @@ config HID_MAYFLASH
>         Say Y here if you have HJZ Mayflash PS3 game controller adapters
>         and want to enable force feedback support.
>
> +config HID_MICRODIA
> +       tristate "Microdia based keyboards"
> +       depends on HID
> +       default !EXPERT
> +       ---help---
> +    Support for Microdia devices that are not compliant with the HID standard.
> +
> +    One known example if the Redragon Asura Keyboard.
> +
>  config HID_MICROSOFT
>         tristate "Microsoft non-fully HID-compliant devices"
>         depends on HID
> diff --git a/drivers/hid/Makefile b/drivers/hid/Makefile
> index 235bd2a7b333..e66a305876c5 100644
> --- a/drivers/hid/Makefile
> +++ b/drivers/hid/Makefile
> @@ -62,6 +62,7 @@ obj-$(CONFIG_HID_LOGITECH_DJ) += hid-logitech-dj.o
>  obj-$(CONFIG_HID_LOGITECH_HIDPP)       += hid-logitech-hidpp.o
>  obj-$(CONFIG_HID_MAGICMOUSE)   += hid-magicmouse.o
>  obj-$(CONFIG_HID_MAYFLASH)     += hid-mf.o
> +obj-$(CONFIG_HID_MICRODIA)  += hid-microdia.o
>  obj-$(CONFIG_HID_MICROSOFT)    += hid-microsoft.o
>  obj-$(CONFIG_HID_MONTEREY)     += hid-monterey.o
>  obj-$(CONFIG_HID_MULTITOUCH)   += hid-multitouch.o
> @@ -121,4 +122,3 @@ obj-$(CONFIG_USB_KBD)               += usbhid/
>
>  obj-$(CONFIG_I2C_HID)          += i2c-hid/
>
> -obj-$(CONFIG_INTEL_ISH_HID)    += intel-ish-hid/
> diff --git a/drivers/hid/hid-core.c b/drivers/hid/hid-core.c
> index 0c3f608131cf..b36c2df4b755 100644
> --- a/drivers/hid/hid-core.c
> +++ b/drivers/hid/hid-core.c
> @@ -2393,6 +2393,9 @@ static const struct hid_device_id hid_have_special_driver[] = {
>  #endif
>  #if IS_ENABLED(CONFIG_HID_ZYDACRON)
>         { HID_USB_DEVICE(USB_VENDOR_ID_ZYDACRON, USB_DEVICE_ID_ZYDACRON_REMOTE_CONTROL) },
> +#endif
> +#if IS_ENABLED(CONFIG_HID_MICRODIA)
> +       { HID_USB_DEVICE(USB_VENDOR_ID_MICRODIA,  USB_DEVICE_ID_REDRAGON_ASURA) },
>  #endif

You don't need this hunk anymore since v4.15 IIRC

>         { }
>  };
> diff --git a/drivers/hid/hid-ids.h b/drivers/hid/hid-ids.h
> index 5da3d6256d25..146869e55c5a 100644
> --- a/drivers/hid/hid-ids.h
> +++ b/drivers/hid/hid-ids.h
> @@ -1171,4 +1171,7 @@
>  #define USB_VENDOR_ID_UGTIZER                  0x2179
>  #define USB_DEVICE_ID_UGTIZER_TABLET_GP0610    0x0053
>
> +#define USB_VENDOR_ID_MICRODIA          0x0c45
> +#define USB_DEVICE_ID_REDRAGON_ASURA    0x760b
> +
>  #endif
> diff --git a/drivers/hid/hid-microdia.c b/drivers/hid/hid-microdia.c
> new file mode 100644
> index 000000000000..f9d8de18a989
> --- /dev/null
> +++ b/drivers/hid/hid-microdia.c
> @@ -0,0 +1,148 @@

missing the SPDX identifier
(see Documentation/process/license-rules.rst)

> +/*
> + *  HID driver for Microdia-based keyboards
> + *
> + *  Copyright (c) 2017 Robert Munteanu
> + */
> +
> +/*
> + * This program is free software; you can redistribute it and/or modify it
> + * under the terms of the GNU General Public License as published by the Free
> + * Software Foundation; either version 2 of the License, or (at your option)
> + * any later version.
> + */
> +
> +#include <linux/device.h>
> +#include <linux/input.h>
> +#include <linux/hid.h>
> +#include <linux/module.h>
> +#include <linux/log2.h>
> +#include <linux/input-event-codes.h>
> +
> +#include "hid-ids.h"
> +
> +
> +// The microdia family of keyboards uses a non-standard way of sending
> +// modifier keys

Unless it has changed since last time I checked, we do not use C++ comments
(see Documentation/process/coding-style.rst)

> +//
> +// The down event always sets the first bit to 0x04 and the second keycode
> +// to a custom value. For instance, left shift sends the following bits
> +//
> +//   04 02 00 00 00 00 00 00
> +//
> +// while left control sends
> +//
> +//   04 01 00 00 00 00 00 00
> +//
> +// Unfortunately these are all mapped to left shift and the keyboard is
> +// non-functional in that respect. To solve the problem, we capture the
> +// raw data in raw_event and manually generate the correct input events
> +//
> +// TODO
> +//
> +// 1. Some modifiers keys still don't work, e.g. Ctrl-Shift-P
> +//    Interestingly enough, this happens when pressing the physical
> +//    left shift key, but now when pressing the physical right shift key.
> +//    hexdump does not show them either.
> +// 2. A second USB keyboard is registered, but it should be removed
> +// 3. Modifier keys sometimes get stuck, need to re-press to clear
> +
> +static int microdia_input_configured(struct hid_device *hdev,
> +       struct hid_input *hi)
> +{
> +
> +       hid_info(hdev, "Keyboard configured with limited support (modifier keys may get stuck, some modifiers combinations with left-shift not working) ");
> +
> +       hid_set_drvdata(hdev, hi);
> +
> +       return 0;
> +}
> +
> +static int microdia_input_mapping(struct hid_device *hdev, struct hid_input *hi,
> +               struct hid_field *field, struct hid_usage *usage,
> +               unsigned long **bit, int *max)
> +{
> +       // do not map left shift since we will manually generate input
> +       // events in microdia_raw_event
> +       if ((usage->hid & HID_USAGE_PAGE) == HID_UP_KEYBOARD)
> +               if ((usage->hid & HID_USAGE) == 0xe1)
> +                       return -1;
> +
> +       return 0;
> +}
> +
> +// array index of a modifier matches the bit index in the data payload
> +// the modifier data is always stored in the second int
> +// e.g. for left alt the 1 bit is set - 04 04 ...
> +// TODO - second entry should be left shift, but that's not possible
> +// since we ignore it in the mapping
> +static int microdia_modifiers[7] = {
> +               KEY_LEFTCTRL,
> +               KEY_RIGHTSHIFT,
> +               KEY_LEFTALT,
> +               KEY_LEFTMETA,
> +               KEY_RIGHTCTRL,
> +               KEY_RIGHTSHIFT,
> +               KEY_RIGHTALT
> +};
> +
> +static int microdia_last_handled_modifier;
> +
> +static int microdia_raw_event(struct hid_device *hdev,
> +               struct hid_report *report, u8 *data, int size)
> +{
> +       int i, changed_key, new_value, mapped_key;
> +       struct hid_input *hi;
> +
> +       // 1. validate that we get 8 bits of the for 04 xx 00 00 00 00 00 00
> +       if (size != 8)
> +               return 0;
> +
> +       if (data[0] != 4)
> +               return 0;
> +
> +       // TODO - can I somehow use a bit mask? data & 0x00ffffff != 0
> +       for (i = 2; i < size; i++)
> +               if (data[i] != 0)
> +                       return 0;
> +
> +       // TODO - don't process the keyup event 04 00 00 00 00 00 00 00

That's a lot of TODO in such a simple driver :/

> +       // if we don't expect a modifier key 'up' event
> +
> +       // 2. detect based on previous data what key was pressed or depressed
> +       // a key was pressed or depressed if its bit has a different value
> +       // between this and the previous invocation. If the bit is set
> +       // it was pressed
> +
> +       changed_key = data[1] ^ microdia_last_handled_modifier;
> +       new_value = (data[1] & changed_key) != 0;
> +       // TODO - is ilog2 really needed?
> +       mapped_key = microdia_modifiers[ilog2(changed_key)];

What if you get 2 changed keys at a time?

Anyway, before giving you a ACK or NACK on the driver, the behavior
from the keyboard firmware looks sane and pretty common. So my guess
is that there is something wrong in the report descriptors, and I need
the hid-recorder output to have a better idea of what is wrong with
our current handling of this keyboard.

Cheers,
Benjamin

> +
> +       // 3. report the key event and track what was sent
> +       hi = hid_get_drvdata(hdev);
> +
> +       input_report_key(hi->input, mapped_key, new_value);
> +
> +       microdia_last_handled_modifier = data[1];
> +
> +       return 1;
> +}
> +
> +static const struct hid_device_id microdia_devices[] = {
> +       {HID_USB_DEVICE(USB_VENDOR_ID_MICRODIA, USB_DEVICE_ID_REDRAGON_ASURA)},
> +       {}
> +};
> +
> +MODULE_DEVICE_TABLE(hid, microdia_devices);
> +
> +static struct hid_driver microdia_driver = {
> +       .name = "microdia",
> +       .input_mapping = microdia_input_mapping,
> +       .id_table = microdia_devices,
> +       .raw_event = microdia_raw_event,
> +       .input_configured = microdia_input_configured,
> +};
> +
> +module_hid_driver(microdia_driver);
> +
> +MODULE_LICENSE("GPL");
> --
> 2.16.2
>