linux-kernel - Re: [patch 0/2] add actuators support

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Date:   Mon, 17 Jul 2017 18:40:06 +0200
From:   Greg KH <gregkh@...uxfoundation.org>
To:     Jiri Pirko <jiri@...nulli.us>
Cc:     linux-kernel@...r.kernel.org, davem@...emloft.net,
        mchehab@...nel.org, jikos@...nel.org
Subject: Re: [patch 0/2] add actuators support

On Mon, Jul 17, 2017 at 06:34:58PM +0200, Jiri Pirko wrote:
> Mon, Jul 17, 2017 at 06:28:38PM CEST, gregkh@...uxfoundation.org wrote:
> >On Mon, Jul 17, 2017 at 06:19:12PM +0200, Jiri Pirko wrote:
> >> From: Jiri Pirko <jiri@...lanox.com>
> >> 
> >> I am owner of height adjustable desk and naturally, as it has an USB
> >> interface, I need to controll it from my computer. Started to think
> >> about what would be the best way, I realized that I need to introduce
> >> a new driver class in kernel. The reason is a need to have one API
> >> for all possible kinds of actuator devices (USB, I2C, gpio, etc).
> >
> >Why does this have to be a kernel driver at all?  Your USB driver should
> >really just be a simple userspace application (use libusb to have it
> >work on all operating systems.)
> 
> Yeah, I was thinking about it as well. To have some kind of single
> purpose app like sispmctl (control of surge protector). But that would
> limit you only for this specific device. And for multiple devices you
> would have to have multiple apps.
> 
> So it seems to me like a suitable solution to have this as a driver
> class.

For USB devices, especially ones as simple as this, we don't want them
to have kernel drivers.  It's just overkill.

And never create a class if you only have one type of device, otherwise
you don't know if you really have it properly defined or not.  3 is a
good number to start with.

sorry,

greg k-h