From mboxrd@z Thu Jan 1 00:00:00 1970 From: Paul Mackerras Subject: Re: [PATCH 1/2] [PCI] Check that MWI bit really did get set Date: Mon, 16 Oct 2006 10:44:30 +1000 Message-ID: <17714.54766.390707.532248@cargo.ozlabs.ibm.com> References: <1160161519800-git-send-email-matthew@wil.cx> <20061015191631.DE49D19FEC8@adsl-69-226-248-13.dsl.pltn13.pacbell.net> <20061015123432.4c6b7f15.akpm@osdl.org> <200610151545.59477.david-b@pacbell.net> <20061015161834.f96a0761.akpm@osdl.org> <1160956960.5732.99.camel@localhost.localdomain> <20061015164402.f9b8b4d2.akpm@osdl.org> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit Cc: Alan Cox , David Brownell , matthew@wil.cx, val_henson@linux.intel.com, netdev@vger.kernel.org, linux-pci@atrey.karlin.mff.cuni.cz, linux-kernel@vger.kernel.org, gregkh@suse.de Return-path: To: Andrew Morton In-Reply-To: <20061015164402.f9b8b4d2.akpm@osdl.org> Sender: linux-kernel-owner@vger.kernel.org List-Id: netdev.vger.kernel.org Andrew Morton writes: > Let me restore the words from my earlier email which you removed so that > you could say that: > > For you the driver author to make assumptions about what's happening > inside pci_set_mwi() is a layering violation. Maybe the bridge got > hot-unplugged. Maybe the attempt to set MWI caused some synchronous PCI > error. For example, take a look at the various implementations of > pci_ops.read() around the place - various of them can fail for various > reasons. Maybe aliens are firing a ray-gun at the card. I think it's fundamentally wrong for the driver to deny service completely because of a maybe. Either there was a transient error that only affected the attempt to set MWI, in which case a printk (inside pci_set_mwi!) is appropriate, and we carry on. Or there is a persistent error condition, in which case the driver will see something else fail soon enough - something that the driver actually needs to have working in order to operate - and fail at that point. For the driver to stop and refuse to go any further because of an error in pci_set_mwi has far more disadvantages than advantages. Paul.