From owner-freebsd-current@FreeBSD.ORG Mon Jul 9 03:31:46 2012 Return-Path: Delivered-To: freebsd-current@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [69.147.83.52]) by hub.freebsd.org (Postfix) with ESMTP id E41521065673 for ; Mon, 9 Jul 2012 03:31:46 +0000 (UTC) (envelope-from imp@bsdimp.com) Received: from mail-pb0-f54.google.com (mail-pb0-f54.google.com [209.85.160.54]) by mx1.freebsd.org (Postfix) with ESMTP id AD29B8FC1E for ; Mon, 9 Jul 2012 03:31:46 +0000 (UTC) Received: by pbbro2 with SMTP id ro2so19804940pbb.13 for ; Sun, 08 Jul 2012 20:31:46 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20120113; h=sender:subject:mime-version:content-type:from:in-reply-to:date:cc :content-transfer-encoding:message-id:references:to:x-mailer :x-gm-message-state; bh=s0Nw9VUfRbX8IqJVyeJxrQ2ZD0MN1pqek1LCN5jPloU=; b=F4eCDDTxhNJq57pW83gJVpuA/y8iu+NsTaEKWeJ/ydOi06O4C2qivfW7m1vKPbLS0B ljjDG/Ehr0USILwnpfF9y4W4RVxn7LET+VAgwy962SStkCNsjB68GfVk3N3JHGFIbF3Z 7z3ipsGuS6KCpZIu+pjIHKolT64XZRdcm7u+rFhgfe6Ul//kCgY+0dL5OXHxW/WMEzc9 DOKa1CKFGvk0BmFLjZj2vk3m2KxIDVaQ/0TeSG/btvlZ8YnX4uwJELre2POJHf795c26 vVsHjzJ4+q4iLL+gYwmmroGoplCJvlD3idqTJI8W1RansrmL3EBParm+OGxWFq29MZEO Rleg== Received: by 10.68.132.166 with SMTP id ov6mr57538341pbb.24.1341804706256; Sun, 08 Jul 2012 20:31:46 -0700 (PDT) Received: from [10.0.0.63] (50-78-194-198-static.hfc.comcastbusiness.net. [50.78.194.198]) by mx.google.com with ESMTPS id pc6sm17677069pbc.47.2012.07.08.20.31.44 (version=TLSv1/SSLv3 cipher=OTHER); Sun, 08 Jul 2012 20:31:45 -0700 (PDT) Sender: Warner Losh Mime-Version: 1.0 (Apple Message framework v1084) Content-Type: text/plain; charset=us-ascii From: Warner Losh In-Reply-To: Date: Sun, 8 Jul 2012 21:31:37 -0600 Content-Transfer-Encoding: quoted-printable Message-Id: <5C18109D-E7A8-4868-BEA9-26B63360BB24@bsdimp.com> References: <31A0DCE7-3B93-41BC-805A-E0B163892112@bsdimp.com> To: Arnaud Lacombe X-Mailer: Apple Mail (2.1084) X-Gm-Message-State: ALoCoQlE5BDVwpHRnFFJGgxXtUw2Q6mVCTgau30S4d7VLcEaNUMTmXTkw2AO0IyJZFpL2ZsMADeQ Cc: FreeBSD Hackers , FreeBSD Current Subject: Re: newbus' ivar's limitation.. X-BeenThere: freebsd-current@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: Discussions about the use of FreeBSD-current List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Mon, 09 Jul 2012 03:31:47 -0000 On Jul 8, 2012, at 9:26 PM, Arnaud Lacombe wrote: > Hi, >=20 > On Sun, Jul 8, 2012 at 10:07 PM, Warner Losh wrote: >>=20 >> On Jul 8, 2012, at 7:22 PM, Arnaud Lacombe wrote: >>> Ok, yet another Newbus' limitation. Assuming a device exports more >>> than one interface, and one of its child has need to use more than = one >>> interface, each interfaces cannot register, concurrently, its own >>> ivar. While I try to always have a single child per >>> interface/resource, I need to keep some compatibility with the old = way >>> of doing thing (POLA wrt. drivers I cannot/will not convert and >>> userland). So, it would have been nice if ivar had been = per-interface, >>> not global and unique to one device. >>=20 >> There's one pointer for the ivars. The bus code gets to determine = what the ivar looks like, because the interface is totally private to = the bus. So long as it returns the right thing for any key that's = presented, it doesn't matter quite how things are done. >>=20 >> So I'm not sure I understand what you are saying here. >>=20 > dev0 implements two interfaces: A and B. dev1, child of dev0, needs to > use both interfaces. There is no generic way for dev0 to export > independent ivars for both interface. For now, I restricted the > function of the second interface not to need ivar, but that's kind of > hackish. Only if the IVARs for interface A and interface B have overlapping = values. If the Ivar keys don't overlap, then there's no problems at = all. Certainly less hackish than not using them at all. Since dev0 = knows the layout of the ivar that it set on its child, this presents no = problems at all. It would return the values from A from the right part = of the ivar, and those from B in the right part. Apart from the = coordination of Ivar numbers, as I outlined in my last post, there's no = issue here. Warner > - Arnaud >=20 >> The problem, more basically, is that the ivar keys are not unique. = Currently, there's no bits used in the key to define the values to be = non-overlapping. For example: >> enum pci_device_ivars { >> PCI_IVAR_SUBVENDOR, >> PCI_IVAR_SUBDEVICE, >> PCI_IVAR_VENDOR, >> .... >> }; >>=20 >> We could easily reserve the upper 16-bits of this field to be that = key. This value could then be used to differentiate them. But this = wouldn't scale too well. Given that there's only about a dozen or two = in the tree, that's right at the moment, it wouldn't be hard to do = something like: >>=20 >> enum ivar_namespace { >> IVAR_PCI =3D 1, >> IVAR_PCCARD, >> IVAR_USB, >> etc >> }; >> #define IVAR_SHIFT 16 >>=20 >> and the above could be changed to: >>=20 >> enum pci_device_ivars { >> PCI_IVAR_SUBVENDOR =3D IVAR_PCI << IVAR_SHIFT, >> PCI_IVAR_SUBDEVICE, >> PCI_IVAR_VENDOR, >> .... >> }; >>=20 >> and then we'd have an unambiguous key, and the bus could easily = implement multiple interfaces. >>=20 >> but then again, most of the existing interfaces in the kernel are = mutually exclusive, so you could implement this just for your new = interfaces. >>=20 >>> Unless I am mistaken, ivar are the only way for a parent can = transmit >>> information to a child. I can not simply implement a new METHOD to = get >>> that ivar as the device implements multiple time the same function >>> (actually, up to 4 time for one, 3 for the other, with possible >>> crossovers...), each one physically distinct. Each child is being = tied >>> to a pair. Thus, I need to pass each child discriminator(s) for each >>> interfaces right after having been *created*, which cannot be done >>> later on. Of course, it is out-of-question to have crossover in the >>> interfaces definitions. >>=20 >> ivars are but one way to communicate this. However, they are the = generic way to convert a key to a value and store a key on a value. I = don't really understand what you are trying to say here, perhaps an = example would help illustrate what you are trying to do, since I don't = quite understand the problem here. >>=20 >>> The best way I could achieve this currently is to pass the child's >>> device to its parent, and do a lookup based on that pointer to get >>> information I need, but erk.... >>=20 >> That doesn't make any sense. The child's parent already sets that = child's ivar when the child is created. The child's parent already gets = a pointer to the child when asked to do the key to value translation. = Again, perhaps an example would help here. >>=20 >> Warner