From mboxrd@z Thu Jan 1 00:00:00 1970 From: bhelgaas@google.com (Bjorn Helgaas) Date: Wed, 30 Jan 2013 13:48:33 -0700 Subject: [PATCH v2 05/27] arm: pci: add a align_resource hook In-Reply-To: <20130130124721.0ad0294e@skate> References: <1359399397-29729-1-git-send-email-thomas.petazzoni@free-electrons.com> <201301292254.01069.arnd@arndb.de> <20130130042103.GB5734@obsidianresearch.com> <201301300955.49473.arnd@arndb.de> <20130130124721.0ad0294e@skate> Message-ID: To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org On Wed, Jan 30, 2013 at 4:47 AM, Thomas Petazzoni wrote: > So what I'm going to do now is rework my patch series by removing the > emulated host bridge (which is normally mandatory by PCIe standard, but > Linux doesn't need it, so we don't care), ... This is a tangent since you're removing the emulated host bridge anyway, but it's been mentioned a couple of times, and I'd like to understand this. Jason mentioned earlier in the [07/27] emulated host bridge thread that the PCIe spec requires a host bridge at 00:00.0. I've never seen that mentioned in the spec; can somebody point me to the actual requirement that host bridges appear in config space? My understanding has been that host bridges, whether PCI or PCIe, are required to *exist*, but that the way you enumerate them and configure them is outside the scope of the PCI/PCIe specs. I know that many chips, especially for x86, *do* make the host bridge appear in config space, but I've never seen a requirement for that. Bjorn