Date: Wed, 21 Jan 2009 16:12:23 +0200 From: Andriy Gapon <avg@icyb.net.ua> To: Robert Watson <rwatson@FreeBSD.org> Cc: Kostik Belousov <kostikbel@gmail.com>, freebsd-hackers@FreeBSD.org Subject: Re: device driver: cdesw questions? Message-ID: <49772D47.2090602@icyb.net.ua> In-Reply-To: <alpine.BSF.2.00.0901211353440.13974@fledge.watson.org> References: <49770513.8090203@icyb.net.ua> <alpine.BSF.2.00.0901211353440.13974@fledge.watson.org>
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on 21/01/2009 16:05 Robert Watson said the following: > > On Wed, 21 Jan 2009, Andriy Gapon wrote: > >> Question 1: I am writing a driver that would use per-open private data >> (among other features). Do I have to use D_TRACKCLOSE flag in this >> case? In general I am a little bit confused about when d_close is >> invoked. Supposing D_TRACKCLOSE is not set and multiple programs >> concurrently open, use and close a device - when d_close is called - >> when one program closes its last descriptor tied to the device or when >> the system-wide last such descriptor is closed? > > Kostik has already pointed at the cdevpriv API, but just to reiterate > his point: most people will find the semantics of D_TRACKCLOSE confusing > and consider them incorrect, so I would advise against using them. Robert, Kostik, in simplistic layman's terms I need the following - when a particular program "closes my cdev" (explicitly or via exit) I need to catch that and de-allocate certain resources. There can be multiple concurrent programs opening, using and closing my cdev. I guess what you both say is that I shouldn't use D_TRACKCLOSE, instead I should perform the resource management in cdevpriv destructor. Am I guessing correctly this time? -- Andriy Gapon
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