linux-kernel - Re: [PATCH 7/7] misc: intel-ish-client: add intel ishtp clients driver

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Date:   Wed, 4 Jan 2017 20:40:46 +0100
From:   Greg KH <gregkh@...uxfoundation.org>
To:     Srinivas Pandruvada <srinivas.pandruvada@...ux.intel.com>
Cc:     Even Xu <even.xu@...el.com>, jikos@...nel.org,
        benjamin.tissoires@...hat.com, arnd@...db.de,
        andriy.shevchenko@...el.com, linux-input@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 7/7] misc: intel-ish-client: add intel ishtp clients
 driver

On Wed, Jan 04, 2017 at 10:41:26AM -0800, Srinivas Pandruvada wrote:
> On Wed, 2017-01-04 at 18:18 +0100, Greg KH wrote:
> > On Wed, Jan 04, 2017 at 09:11:34AM -0800, Srinivas Pandruvada wrote:
> > > 
> > > On Wed, 2017-01-04 at 14:03 +0100, Greg KH wrote:
> > > > 
> > > > On Fri, Dec 23, 2016 at 09:22:29AM +0800, Even Xu wrote
> > > > > 
> [...]
> 
> > debug should not require a char device node, use debugfs, that is
> > what
> > it is there for.
> > 
> > For "calibration", why not use configfs or even sysfs?
> 
> We will check on this. There is some legacy with the deployed user
> space tools.

Um, you do know that's not a good reason/excuse at all to take incorrect
kernel code, right?  Please don't use that as any kind of excuse.

> > > Basically the ISH provided a standalone low power processor to
> > > developers and manufacturers  to do download some custom algorithms
> > > for
> > > sensors, which may not be compliant to USB HID sensor
> > > specifications
> > > (mostly for IOT space). In that case the user space for those can
> > > communicate using misc driver interface, without adding new kernel
> > > drivers.
> > 
> > So you hide it behind a char device node?  That's not very
> > descriptive
> > or easy to understand :)
> We added several new sensors to IIO and in process of adding new
> sensors to standardize ABI for sensors defined in HID sensor spec.
> 
> Customers can develop and download some algorithm which uses output of
> several sensors and come up with some fusion sensor to detect some
> activity. Either some kernel driver needs to read this and pass this
> event to user space or directly let the user space communicate with the
> firmware using character device. 
> Is there any better way to handle this?
> 
> We want customers to use upstream kernel without out of tree kernel
> drivers.

Why are you somehow claiming this is an either/or kind of situation?
What out-of-tree kernel modules are there?  Why can't they just be
merged if they are somewhere?

Having an interface to add new types of "functionality" is great, and
fine, but why you think a char device node is that type of api is
confusing to me when I already pointed out an number of other potential
solutions.  Have you tried them out and found they do not work?  If so,
great, please explain what is lacking and we can go from there.

If not, please do some basic research first before trying to claim that
a char device is the only possible solution.

You have run this code through the internal Intel kernel developer
review process on their mailing list, correct?  What did they say about
your current design?  If not, why have you not taken advantage of this
resource?

thanks,

greg k-h