Re: [PATCH 1/4] Input: Add new property INPUT_PROP_JOYDEV_IGNORE

[Bastien Nocera <hadess@hadess.net>]

On Thu, 2017-08-24 at 16:11 -0700, Roderick Colenbrander wrote:
> From: Roderick Colenbrander <roderick.colenbrander@sony.com>
> 
> This new property can be set on input devices to blacklist them
> from getting picked up by joydev. This is meant for devices, which
> pass joydev its heuristics, but for which there is no good generic
> way of updating the heuristics.

I can't make sense of that last sentence, and the possessive for
"heuristics" (here and below in the documentation) is, IMO,
unnecessary.

> Signed-off-by: Roderick Colenbrander <roderick.colenbrander@sony.com>
> ---
>  Documentation/input/event-codes.rst    | 9 +++++++++
>  include/uapi/linux/input-event-codes.h | 1 +
>  2 files changed, 10 insertions(+)
> 
> diff --git a/Documentation/input/event-codes.rst
> b/Documentation/input/event-codes.rst
> index a8c0873..ae8c546 100644
> --- a/Documentation/input/event-codes.rst
> +++ b/Documentation/input/event-codes.rst
> @@ -356,6 +356,15 @@ can report through the rotational axes (absolute
> and/or relative rx, ry, rz).
>  All other axes retain their meaning. A device must not mix
>  regular directional axes and accelerometer axes on the same event
> node.
>  
> +INPUT_PROP_JOYDEV_IGNORE
> +------------------------
> +
> +The joydev interface uses heuristics to determine whether it should
> expose an
> +input device through joydev. Some devices pass its heuristics, but
> don't
> +make sense to expose. In some cases the generic heuristics can be
> updated,
> +but in other cases this is not easy. The INPUT_PROP_JOYDEV_IGNORE
> flag can
> +be set by drivers to explicit request blacklisting by joydev.

The "don't make sense to expose" is not what we're trying to do here
though. The problem is rather that "we used not to show this device
through joydev, but programs using joydev are limited and usually not
updated so we should only show what we used to".

>  Guidelines
>  ==========
>  
> diff --git a/include/uapi/linux/input-event-codes.h
> b/include/uapi/linux/input-event-codes.h
> index 1798910..f6aac0e 100644
> --- a/include/uapi/linux/input-event-codes.h
> +++ b/include/uapi/linux/input-event-codes.h
> @@ -26,6 +26,7 @@
>  #define INPUT_PROP_TOPBUTTONPAD		0x04	/*
> softbuttons at top of pad */
>  #define INPUT_PROP_POINTING_STICK	0x05	/* is a
> pointing stick */
>  #define INPUT_PROP_ACCELEROMETER	0x06	/* has
> accelerometer */
> +#define INPUT_PROP_JOYDEV_IGNORE	0x07	/* hint to
> ignore device by joydev */
>  
>  #define INPUT_PROP_MAX			0x1f
>  #define INPUT_PROP_CNT			(INPUT_PROP_MAX + 1)