From mboxrd@z Thu Jan 1 00:00:00 1970 From: Mark Lord Subject: libata, devm_*, and MSI ? Date: Tue, 20 Jan 2009 11:03:13 -0500 Message-ID: <4975F5C1.8090107@rtr.ca> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Return-path: Sender: linux-pci-owner@vger.kernel.org To: IDE/ATA development list , Linux Kernel , Tejun Heo , Jeff Garzik , linux-pci@vger.kernel.org List-Id: linux-ide@vger.kernel.org Tejun / Jeff, I am working on MSI support for sata_mv, and am trying to puzzle out exactly what the kernel expects for this. Looking at other drivers, both libata and otherwise, yields a variety of conflicting implementations. For starters, the MSI HOW-TO suggests that drivers must be careful to invoke pci_disable_msi() on module unload, but I don't see that happening anywhere in libata. Unless, Tejun, the devm_* routines automatically do this.. do they? Next, there's no mention of a need for invoking pci_intx() in the HOW-TO, yet some device drivers call it, and others do not. Eg. from ahci.c, we have this: if ((hpriv->flags & AHCI_HFLAG_NO_MSI) || pci_enable_msi(pdev)) pci_intx(pdev, 1); Which agrees with the existing code in sata_mv: if (msi && pci_enable_msi(pdev)) pci_intx(pdev, 1); Which seems to call pci_intx() only when MSI is *not* used. Fine. But then in sata_vsc.c, we do sort of the opposite: if (pci_enable_msi(pdev) == 0) pci_intx(pdev, 0); Either that one is wrong, or pci_intx() is unnecessary in all cases. Again, the MSI HOW-TO doesn't even mention this routine. Looking through the network drivers, it seems that some of them do the pci_intx(pdev,1) call for the cases where pci_enable_msi() fails, similar to ahci.c and sata_mv.c. But not all of them do that. Perhaps somebody from the PCI side of things might enlighten us all. Thanks