linux-kernel - Re: [RFC] HID:hid-lg4ff: Delay to allow wheels to center after plug-in

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Date:   Wed, 26 Oct 2016 09:36:27 +0200
From:   Michal Malý <madcatxster@...il.com>
To:     Simon Wood <gitsend@...gewell.org>
Cc:     linux-input@...r.kernel.org, linux-kernel@...r.kernel.org,
        Jiri Kosina <jkosina@...e.cz>, Edwin Velds <edwin@...ds.nl>,
        Elias Vanderstuyft <elias.vds@...il.com>,
        Simon Wood <simon@...gewell.org>
Subject: Re: [RFC] HID:hid-lg4ff: Delay to allow wheels to center after plug-in

Hi all,

maybe instead of stalling the entire init() function it'd be better to put a 
request to disable autocentering on a workqueue and start a delayed work once 
the init() function is done setting the wheel up? There'd be a bit more code 
to write though...

Michal

On Tuesday, October 25, 2016 7:26:12 PM CEST Simon Wood wrote:
> A number of wheels (G27/etc) do a little full right/full left 'dance'
> when first plugged in. This patch inserts a delay so that this 'dance'
> is completed before we disable (set to zero) the autocenter spring.
> 
> A side benefit is that the DFGT was confused without the delay, and is
> now correctly being set to 900' rotation mode.
> 
> Side Effect - and the reason I am sending as RFC. This 8s delay seems
> to have an effect on other wheels connected at the same time.
> 
> With 3 wheels on a hub, and then the hub connected to PC. The wheel
> on the right in video below waits for G27 to complete this 8s, before
> it will do it's 'dance' and register with the system.
> 
> https://www.youtube.com/watch?v=xCVpCw_yGgA
> 
> I don't know if this is a problem, or if someone here has suggestions
> on a better way to implement the delay...
> ---
>  drivers/hid/hid-lg4ff.c | 10 ++++++++++
>  1 file changed, 10 insertions(+)
> 
> diff --git a/drivers/hid/hid-lg4ff.c b/drivers/hid/hid-lg4ff.c
> index af3a8ec..3eee920 100644
> --- a/drivers/hid/hid-lg4ff.c
> +++ b/drivers/hid/hid-lg4ff.c
> @@ -1248,6 +1248,8 @@ int lg4ff_init(struct hid_device *hid)
>  	/* Check if autocentering is available and
>  	 * set the centering force to zero by default */
>  	if (test_bit(FF_AUTOCENTER, dev->ffbit)) {
> +		wait_queue_head_t wait;
> +
>  		/* Formula Force EX expects different autocentering command */
>  		if ((bcdDevice >> 8) == LG4FF_FFEX_REV_MAJ &&
>  		    (bcdDevice & 0xff) == LG4FF_FFEX_REV_MIN)
> @@ -1255,6 +1257,14 @@ int lg4ff_init(struct hid_device *hid)
>  		else
>  			dev->ff->set_autocenter = lg4ff_set_autocenter_default;
> 
> +		/* insert a 8s delay to allow DFGT/G25/G27/G29 wheels to return to 
center
> position*/ +		if (lg4ff_devices[i].product_id ==
> USB_DEVICE_ID_LOGITECH_DFGT_WHEEL || +				
lg4ff_devices[i].product_id ==
> USB_DEVICE_ID_LOGITECH_G25_WHEEL || +				lg4ff_devices[i].product_id 
==
> USB_DEVICE_ID_LOGITECH_G27_WHEEL || +				lg4ff_devices[i].product_id 
==
> USB_DEVICE_ID_LOGITECH_G29_WHEEL) { +			init_waitqueue_head (&wait);
> +			wait_event_interruptible_timeout(wait, 0, msecs_to_jiffies(8000));
> +		}
>  		dev->ff->set_autocenter(dev, 0);
>  	}