linux-kernel - Re: [PATCH v5 4/5] Input: cs40l50 - Add support for the CS40L50 haptic driver

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Date: Fri, 12 Jan 2024 15:41:32 +0000
From: James Ogletree <James.Ogletree@...rus.com>
To: Dmitry Torokhov <dmitry.torokhov@...il.com>
CC: James Ogletree <jogletre@...nsource.cirrus.com>,
        Fred Treven
	<Fred.Treven@...rus.com>,
        Ben Bright <Ben.Bright@...rus.com>, Rob Herring
	<robh+dt@...nel.org>,
        Krzysztof Kozlowski
	<krzysztof.kozlowski+dt@...aro.org>,
        Conor Dooley <conor+dt@...nel.org>,
        Simon Trimmer <simont@...nsource.cirrus.com>,
        Charles Keepax
	<ckeepax@...nsource.cirrus.com>,
        Richard Fitzgerald
	<rf@...nsource.cirrus.com>,
        Lee Jones <lee@...nel.org>, Liam Girdwood
	<lgirdwood@...il.com>,
        Mark Brown <broonie@...nel.org>, Jaroslav Kysela
	<perex@...ex.cz>,
        Takashi Iwai <tiwai@...e.com>,
        James Schulman
	<James.Schulman@...rus.com>,
        David Rhodes <David.Rhodes@...rus.com>,
        Alexandre Belloni <alexandre.belloni@...tlin.com>,
        Peng Fan
	<peng.fan@....com>, Jeff LaBundy <jeff@...undy.com>,
        Sebastian Reichel
	<sebastian.reichel@...labora.com>,
        Jacky Bai <ping.bai@....com>, Weidong Wang
	<wangweidong.a@...nic.com>,
        Arnd Bergmann <arnd@...db.de>,
        Herve Codina
	<herve.codina@...tlin.com>,
        Shuming Fan <shumingf@...ltek.com>,
        Shenghao Ding
	<13916275206@....com>, Ryan Lee <ryans.lee@...log.com>,
        Linus Walleij
	<linus.walleij@...aro.org>,
        "open list:CIRRUS LOGIC HAPTIC DRIVERS"
	<patches@...nsource.cirrus.com>,
        "open list:INPUT (KEYBOARD, MOUSE, JOYSTICK,
 TOUCHSCREEN)..." <linux-input@...r.kernel.org>,
        "open list:OPEN FIRMWARE AND
 FLATTENED DEVICE TREE BINDINGS" <devicetree@...r.kernel.org>,
        open list
	<linux-kernel@...r.kernel.org>,
        "open list:SOUND - SOC LAYER / DYNAMIC AUDIO
 POWER MANAGEM..." <linux-sound@...r.kernel.org>,
        "moderated list:CIRRUS LOGIC
 AUDIO CODEC DRIVERS" <alsa-devel@...a-project.org>
Subject: Re: [PATCH v5 4/5] Input: cs40l50 - Add support for the CS40L50
 haptic driver



> On Jan 11, 2024, at 1:28 AM, Dmitry Torokhov <dmitry.torokhov@...il.com> wrote:
> 
> On Wed, Jan 10, 2024 at 02:36:55PM +0000, James Ogletree wrote:
>> 
>>> On Jan 9, 2024, at 4:31 PM, Dmitry Torokhov <dmitry.torokhov@...il.com> wrote:
>>> 
>>> On Tue, Jan 09, 2024 at 10:03:02PM +0000, James Ogletree wrote:
>>>> 
>>>> 
>>>>> On Jan 6, 2024, at 7:58 PM, Dmitry Torokhov <dmitry.torokhov@...il.com> wrote:
>>>>> 
>>>>> On Thu, Jan 04, 2024 at 10:36:37PM +0000, James Ogletree wrote:
>>>>>> + } else {
>>>>>> + queue_work(info->vibe_wq, &info->vibe_stop_work);
>>>>> 
>>>>> Which effect are you stopping? All of them? You need to stop a
>>>>> particular one.
>>>> 
>>>> Our implementation of “stop” stops all effects in flight which is intended.
>>>> That is probably unusual so I will add a comment here in the next
>>>> version.
>>> 
>>> Again, please implement the driver properly, not define your own
>>> carveouts for the expected behavior.
>> 
>> Ack, and a clarification question: the device is not actually able to
>> play multiple effects at once. In that case, does stopping a specific
>> effect entail just cancelling an effect in the queue?
> 
> In this case I believe the device should declare maximum number of
> effects as 1. Userspace is supposed to determine maximum number of
> simultaneously playable effects by issuing EVIOCGEFFECTS ioctl on the
> corresponding event device.

Is it possible to specify the device’s maximum simultaneous effects
without also restricting the number of effects the user can upload? It
looks like both are tied to ff->max_effects.

Best,
James