linux-kernel - Re: [PATCH v6 2/2] staging: ion: create one device entry per heap

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Date:   Mon, 6 Nov 2017 15:46:50 +0100
From:   Greg KH <gregkh@...uxfoundation.org>
To:     Benjamin Gaignard <benjamin.gaignard@...aro.org>
Cc:     Mark Brown <broonie@...nel.org>, Laura Abbott <labbott@...hat.com>,
        Sumit Semwal <sumit.semwal@...aro.org>,
        Arve Hjønnevåg <arve@...roid.com>,
        Riley Andrews <riandrews@...roid.com>,
        Dan Carpenter <dan.carpenter@...cle.com>,
        driverdevel <devel@...verdev.osuosl.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        "dri-devel@...ts.freedesktop.org" <dri-devel@...ts.freedesktop.org>,
        linux-api@...r.kernel.org
Subject: Re: [PATCH v6 2/2] staging: ion: create one device entry per heap

On Mon, Nov 06, 2017 at 03:42:04PM +0100, Benjamin Gaignard wrote:
> 2017-11-02 12:10 GMT+01:00 Mark Brown <broonie@...nel.org>:
> > On Thu, Nov 02, 2017 at 11:44:07AM +0100, Greg KH wrote:
> >> On Tue, Oct 31, 2017 at 07:11:53PM +0000, Mark Brown wrote:
> >
> >> > There was a discussion a while ago in the context of I2C/SPI MFDs
> >> > which concluded that if you need a bus and it's going to be effectively
> >> > noop then you should just use the platform bus as anything else will
> >> > consist almost entirely of cut'n'paste from the platform bus with some
> >> > light sed usage and code duplication is bad.  It's not super lovely as
> >> > it's not actually a memory mapped device but it's the best idea we've
> >> > got.
> >
> >> Ugh, I hate that.  What's wrong with using a "virtual" device instead?
> >
> > It was the duplication, initially everyone was making buses.
> >
> >> I can create a "virtual" bus for things like this if they really want a
> >> "simple" bus, abusing platform for this is the major reason I hate the
> >> platform bus code...
> >
> > In the MFD case they're physical devices, they're just usually on the
> > wrong side of an I2C or SPI link.  Plus MFD already handles platform
> > devices for things that are memory mapped so it's a bit of a more
> > natural fit there.
> 
> What I can do is to register an ion bus (like cec one for example),
> add one ion parent device so heaps will appear in /sys/bus/ion/ion*
> and /sys/devices/ion/ion*
> 
> Does that could sound good enough ?

I would like to see that...

thanks,

greg k-h