On Mon, Jan 13, 2014 at 12:12:20PM -0700, Bjorn Helgaas wrote: > > - nvec = rc; > > - rc = pci_enable_msi_block(pdev, nvec); > > - if (rc) > > + if (pci_enable_msi_range(pdev, nvec, nvec) < 0) > > goto intx; > > > > return nvec; > > > > single_msi: > > - rc = pci_enable_msi(pdev); > > - if (rc) > > + if (pci_enable_msi_range(pdev, 1, 1) < 0) > > This part doesn't seem like an improvement. There are a hundred or so > callers of pci_enable_msi() that only want a single MSI. Is there any > benefit in changing them to use pci_enable_msi_range()? In this particular case it reads better to me as one sees on the screen pci_enable_msi_range(pdev, nvec, nvec) and pci_enable_msi_range(pdev, 1, 1) calls. That allows to avoid switching in mind between negative-or-positive return in the former call and negative-or-zero return from pci_enable_msi() if we had it. But in most cases when single MSI is enabled we do cause complication with the patterns below (which I expect I am going be hated for ;) ): - rc = pci_enable_msi(pdev); - if (rc) + rc = pci_enable_msi_range(pdev, 1, 1); + if (rc < 0) ... - rc = pci_enable_msi(pdev); - if (!rc) + rc = pci_enable_msi_range(pdev, 1, 1); + if (rc > 0) ... I think we have a tradeoff between the interface simplicity and code clarity. What if we try to address both goals by making pci_enable_msi() a helper over pci_enable_msi_range(pdev, 1, 1)? In this case the return value will match negative-or-positive binary semantics while reads almost as good as it used to: - rc = pci_enable_msi(pdev); - if (rc) + rc = pci_enable_msi(pdev); + if (rc < 0) ... - rc = pci_enable_msi(pdev); - if (!rc) + rc = pci_enable_msi(pdev); + if (rc > 0) ... The whole interface would not be inflated as well, with just: diff --git a/Documentation/PCI/MSI-HOWTO.txt b/Documentation/PCI/MSI-HOWTO.txt index a8d0100..fa0b27d 100644 --- a/Documentation/PCI/MSI-HOWTO.txt +++ b/Documentation/PCI/MSI-HOWTO.txt @@ -158,6 +158,9 @@ static int foo_driver_enable_single_msi(struct pci_dev *pdev) return pci_enable_msi_range(pdev, 1, 1); } +A helper function pci_enable_msi() could be used instead. Note, as just +one MSI is requested it could return either a negative errno or 1. + 4.2.2 pci_disable_msi void pci_disable_msi(struct pci_dev *dev) -- Regards, Alexander Gordeev agordeev@xxxxxxxxxx -- To unsubscribe from this list: send the line "unsubscribe linux-ide" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
