Date: Sun, 14 Apr 2013 23:18:44 +0200 From: Marius Strobl <marius@alchemy.franken.de> To: Konstantin Belousov <kostikbel@gmail.com> Cc: svn-src-head@freebsd.org, svn-src-all@freebsd.org, src-committers@freebsd.org Subject: Re: svn commit: r249476 - in head/sys/dev: ata pci Message-ID: <20130414211844.GB62578@alchemy.franken.de> In-Reply-To: <20130414205222.GG2930@kib.kiev.ua> References: <201304141402.r3EE2YIi001357@svn.freebsd.org> <20130414150507.GA62578@alchemy.franken.de> <20130414205222.GG2930@kib.kiev.ua>
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On Sun, Apr 14, 2013 at 11:52:22PM +0300, Konstantin Belousov wrote: > On Sun, Apr 14, 2013 at 05:05:07PM +0200, Marius Strobl wrote: > > On Sun, Apr 14, 2013 at 02:02:34PM +0000, Konstantin Belousov wrote: > > > Author: kib > > > Date: Sun Apr 14 14:02:34 2013 > > > New Revision: 249476 > > > URL: http://svnweb.freebsd.org/changeset/base/249476 > > > > > > Log: > > > Usnure that PCI bus BIS_GET_DMA_TAG() method sees the actual PCI > > > device which makes the request for dma tag, instead of some descendant > > > of the PCI device, by creating a pass-through trampoline for vga_pci > > > and ata_pci buses. > > > > If you need to know the last PCI device requesting the DMA tag, > > wouldn't it make more sense to let the consumer of this walk up the > > tree as necessary instead of hacking N drivers? I.e.: > > foo_get_dma_tag(device_t bus, device_t child) > > { > > device_t device, parent; > > devclass_t pci_devclass; > > > > pci_devclass = devclass_find("pci"); > > for (device = child; child != bus; device = parent) { > > parent = device_get_parent(device); > > if (device_get_devclass(parent) != pci_devclass) > > continue; > > break; > > } > > /* use device */ > > } > The similar approach was my first thought, and I discussed it with John. > After the discussion, I agreed that this is a hack. > > My understanding is that this default behaviour is only correct for > the simple cases like the one fixed in the commit. Forcing this on > other buses would only make the bugs hidden and cause more efforts > in trying to identify it. Oh, I see that now. Thanks for the clarification. Marius
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