From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from smtp1.linuxfoundation.org (smtp1.linux-foundation.org [172.17.192.35]) by mail.linuxfoundation.org (Postfix) with ESMTPS id B3D8B71 for ; Fri, 29 Jul 2016 08:14:33 +0000 (UTC) Received: from www381.your-server.de (www381.your-server.de [78.46.137.84]) by smtp1.linuxfoundation.org (Postfix) with ESMTPS id 1C9FDFC for ; Fri, 29 Jul 2016 08:14:32 +0000 (UTC) To: Hans Verkuil , "Luis R. Rodriguez" , Mark Brown References: <20160727172636.GM11806@sirena.org.uk> <20160727175829.GG5537@wotan.suse.de> <579A7DFD.60305@metafoo.de> <98eb563b-5d62-74df-692a-f2aa4f7b07b8@xs4all.nl> From: Lars-Peter Clausen Message-ID: Date: Fri, 29 Jul 2016 09:55:58 +0200 MIME-Version: 1.0 In-Reply-To: <98eb563b-5d62-74df-692a-f2aa4f7b07b8@xs4all.nl> Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: 7bit Cc: ksummit-discuss@lists.linuxfoundation.org, Mauro Carvalho Chehab , "vegard.nossum@gmail.com" , "rafael.j.wysocki" , Marek Szyprowski , Valentin Rothberg Subject: Re: [Ksummit-discuss] [TECH TOPIC] Addressing complex dependencies and semantics (v2) List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , On 07/29/2016 09:45 AM, Hans Verkuil wrote: > > > On 07/28/2016 11:49 PM, Lars-Peter Clausen wrote: >> On 07/27/2016 07:58 PM, Luis R. Rodriguez wrote: >>> On Wed, Jul 27, 2016 at 06:26:36PM +0100, Mark Brown wrote: >>>>> to help enable asynchronous probe, however for built-in devices this requires >>>>> very specific platform knowledge otherwise using async probe will blow up >>>>> your kernel -- if you get it right though, using async probe can help with >>>> >>>> I'm not sure what specific platform knowledge you're thinking of here? >>>> We have coverage for most things in the form of deferred probe (messy >>>> though it is). >>> >>> Deferred probe is a complete a hack and sub-optimal. >> >> I fully agree. In the past though there were a few good attempts of >> providing something better than probe deferral, but those were always >> quickly shutdown by GregKH for failing to prove that probe deferral >> really is insufficient. >> >> This probably an issue of presentation, but for future attempts it >> should be kept in mind that hard numbers on why this is better greatly >> improve the chance of it being accepted. > > 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. > > That code allows a bridge driver to wait until all dependent drivers are probed. > This really should be core functionality. > > Do other subsystems do something similar like drivers/media/v4l2-core/v4l2-async.c? > Does anyone know? drivers/base/component.c is a subsystem independent approach to the same problem and is used by a few subsystems (primarily DRM).