Date: Wed, 21 Jan 2009 16:15:09 +0200 From: Kostik Belousov <kostikbel@gmail.com> To: Andriy Gapon <avg@icyb.net.ua> Cc: freebsd-hackers@FreeBSD.org, Robert Watson <rwatson@FreeBSD.org> Subject: Re: device driver: cdesw questions? Message-ID: <20090121141509.GN58517@deviant.kiev.zoral.com.ua> In-Reply-To: <49772D47.2090602@icyb.net.ua> References: <49770513.8090203@icyb.net.ua> <alpine.BSF.2.00.0901211353440.13974@fledge.watson.org> <49772D47.2090602@icyb.net.ua>
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--+cfQkLQGU7KOA/8T Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On Wed, Jan 21, 2009 at 04:12:23PM +0200, Andriy Gapon wrote: > on 21/01/2009 16:05 Robert Watson said the following: > >=20 > > On Wed, 21 Jan 2009, Andriy Gapon wrote: > >=20 > >> 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? > >=20 > > 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. >=20 > Robert, Kostik, >=20 > 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. >=20 > 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? Yes. This is the purpose of the cdevpriv KPI. --+cfQkLQGU7KOA/8T Content-Type: application/pgp-signature Content-Disposition: inline -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.9 (FreeBSD) iEYEARECAAYFAkl3Le0ACgkQC3+MBN1Mb4gr1gCgwnF62FbmZOVjZ/zlQazR70FO WwcAoLzScUMCpgDy7/LQfJkDz9KI7txK =5R02 -----END PGP SIGNATURE----- --+cfQkLQGU7KOA/8T--
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