From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jeff Garzik Subject: zeroing dev->irq (was Re: [PATCH net-next] tg3: inconsistent interrupt value reported) Date: Fri, 31 Oct 2008 12:47:50 -0400 Message-ID: <490B36B6.2020300@garzik.org> References: <20081031155421.GB6181@gospo.rdu.redhat.com> <490B2DA4.30903@garzik.org> <20081031163851.GA16253@gospo.rdu.redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Cc: mcarlson@broadcom.com, netdev@vger.kernel.org, mchan@broadcom.com, davem@davemloft.net To: Andy Gospodarek Return-path: Received: from srv5.dvmed.net ([207.36.208.214]:46208 "EHLO mail.dvmed.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751382AbYJaQry (ORCPT ); Fri, 31 Oct 2008 12:47:54 -0400 In-Reply-To: <20081031163851.GA16253@gospo.rdu.redhat.com> Sender: netdev-owner@vger.kernel.org List-ID: Andy Gospodarek wrote: > On Fri, Oct 31, 2008 at 12:09:08PM -0400, Jeff Garzik wrote: >> Andy Gospodarek wrote: >>> Systems that use MSI do not report the correct 'Interrupt' value in >>> ifconfig output. This patch sets dev->irq after initializing the >>> interrupt as the value will change when using MSI. >>> >>> I suspect this is a problem with a lot of drivers, so I'll snoop around >>> and post some more patches if needed. >>> >>> Signed-off-by: Andy Gospodarek >>> --- >>> >>> tg3.c | 5 ++++- >>> 1 file changed, 4 insertions(+), 1 deletion(-) >>> >>> diff --git a/drivers/net/tg3.c b/drivers/net/tg3.c >>> index eb9f8f3..fa95e99 100644 >>> --- a/drivers/net/tg3.c >>> +++ b/drivers/net/tg3.c >>> @@ -7892,6 +7892,7 @@ static int tg3_request_irq(struct tg3 *tp) >>> irq_handler_t fn; >>> unsigned long flags; >>> struct net_device *dev = tp->dev; >>> + int ret; >>> if (tp->tg3_flags2 & TG3_FLG2_USING_MSI) { >>> fn = tg3_msi; >>> @@ -7904,7 +7905,9 @@ static int tg3_request_irq(struct tg3 *tp) >>> fn = tg3_interrupt_tagged; >>> flags = IRQF_SHARED | IRQF_SAMPLE_RANDOM; >>> } >>> - return (request_irq(tp->pdev->irq, fn, flags, dev->name, dev)); >>> + ret = request_irq(tp->pdev->irq, fn, flags, dev->name, dev); >>> + dev->irq = tp->pdev->irq; >>> + return ret; >> The ifconfig value is useless, and was never designed to carry and >> display that kind of information (MSI vectors, etc.). >> >> In fact, part of the reason why the ethtool bus-id information was added >> was to give better insight into the hardware attached to the device, >> notably including the interrupt information. >> >> In modern drivers (read: newer than [E]ISA), dev->irq use is >> inconsistent and largely for __best effort__ display purposes only. >> >> I'd argue that a policy of leaving dev->irq at zero might be a better >> idea. That ensures users do not pay attention to what is already an >> inconsistent/truncate/device-dependent piece of information. >> > > This came up because the output is currently wrong. > > # ifconfig eth0 | grep Inter && grep eth0 /proc/interrupts > Interrupt:169 Memory:f6000000-f6012100 > 122: 2894 0 0 PCI-MSI eth0 > > Some drivers take the stand of not setting dev->irq anything (like most > of the Intel drivers), but I didn't take that route with tg3 (or with > the others I'd planned) simply because I didn't want to hear crying > about breaking user-space with a patch that would make that line > disappear. > > If this seems like a reasonable change that we can force on user-space > I'll post a patch that drops the setting of dev->irq all together, so > this disappers. I would vote for zeroing dev->irq in not only tg3, but also other modern, ethtool-enabled drivers... It is a relic of the ISA days, and is incompatible with multiple MSI vector scenarios, something also found on some non-x86 and embedded ethernet drivers. For years now, dev->irq has been providing information on an unreliable, best-effort basis. I prefer definitive, reliable, predictable behaviors, and think always-zero is therefore an improvement. Comments welcome... Jeff