Re: [Ksummit-discuss] [TECH TOPIC] Addressing complex dependencies and semantics (v2)

From: Dmitry Torokhov <dmitry.torokhov@gmail.com>
To: "Luis R. Rodriguez" <mcgrof@kernel.org>
Cc: "Oded Gabbay" <oded.gabbay@gmail.com>,
	"Jörg Rödel" <jroedel@suse.de>,
	ksummit-discuss@lists.linuxfoundation.org,
	"Mauro Carvalho Chehab" <mchehab@osg.samsung.com>,
	"vegard.nossum@gmail.com" <vegard.nossum@gmail.com>,
	"rafael.j.wysocki" <rafael.j.wysocki@intel.com>,
	"Cristina Moraru" <cristina.moraru09@gmail.com>,
	"Roberto Di Cosmo" <roberto@dicosmo.org>,
	"Valentin Rothberg" <valentinrothberg@gmail.com>,
	"Stefano Zacchiroli" <zack@upsilon.cc>,
	"Marek Szyprowski" <m.szyprowski@samsung.com>
Subject: Re: [Ksummit-discuss] [TECH TOPIC] Addressing complex dependencies and semantics (v2)
Date: Mon, 1 Aug 2016 18:03:29 -0700	[thread overview]
Message-ID: <CAKdAkRSgnL_efCUnX+v8Up_OcJq4RcKH=-AHORDwDFWHDXxPAQ@mail.gmail.com> (raw)
In-Reply-To: <20160802005650.GF3296@wotan.suse.de>

On Mon, Aug 1, 2016 at 5:56 PM, Luis R. Rodriguez <mcgrof@kernel.org> wrote:
> On Tue, Aug 02, 2016 at 02:01:56AM +0200, Rafael J. Wysocki wrote:
>> On Monday, August 01, 2016 09:03:09 PM Luis R. Rodriguez wrote:
>> > On Fri, Jul 29, 2016 at 12:13:03PM +0100, Mark Brown wrote:
>> > > On Fri, Jul 29, 2016 at 09:45:55AM +0200, Hans Verkuil wrote:
>> > >
>> > > > My main problem is not so much with deferred probe (esp. for cyclic dependencies
>> > > > it is a simple method of solving this, and simple is good). My main problem is
>> > > > that you can't tell the system that driver A needs to be probed after drivers B,
>> > > > C and D are probed first.
>> > >
>> > > > That would allow us to get rid of v4l2-async.c which is a horrible hack.
>> >
>> > I'd like to understand the requirement for this a bit better, so someone explaining
>> > this would be good if this moves forward as a tech session.
>>
>> One case I'm familiar with is when a device has two (or more) device IDs, where
>> one is more specific than the other.  The idea being that if the OS has a driver
>> for that particular device, it will use the more specific device ID (say A) to
>> look for it, but otherwise it will use the other "generic" ID (say B) to match
>> against a "generic" driver.
>>
>> Of course, that only works if the driver for A is probed before the driver for B.
>
> That's a good case to keep in mind which is indeed complex.

HID would definitely benefit from specific/generic support. Rigth now
there are somewhat long tables of devices generic hid driver ignores
so that specific drivers have a chance to bind.

Thanks.

-- 
Dmitry