PCI/MSI: Add pci_enable_msi() documentation back
We deprecated pci_enable_msi() in 302a2523c277 ("PCI/MSI: Add
pci_enable_msi_range() and pci_enable_msix_range()").
But we changed our minds after noticing that:
- pci_enable_msi() doesn't have confusing return values like
pci_enable_msi_block() and pci_enable_msix() did, and
- pci_enable_msi() has a hundred or so callers that we don't want to
change.
This adds back the pci_enable_msi() documentation.
[bhelgaas: changelog]
Signed-off-by: Alexander Gordeev <agordeev@redhat.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
diff --git a/Documentation/PCI/MSI-HOWTO.txt b/Documentation/PCI/MSI-HOWTO.txt
index a8d0100..3c3080e 100644
--- a/Documentation/PCI/MSI-HOWTO.txt
+++ b/Documentation/PCI/MSI-HOWTO.txt
@@ -82,7 +82,19 @@
has to request that the PCI layer set up the MSI capability for this
device.
-4.2.1 pci_enable_msi_range
+4.2.1 pci_enable_msi
+
+int pci_enable_msi(struct pci_dev *dev)
+
+A successful call allocates ONE interrupt to the device, regardless
+of how many MSIs the device supports. The device is switched from
+pin-based interrupt mode to MSI mode. The dev->irq number is changed
+to a new number which represents the message signaled interrupt;
+consequently, this function should be called before the driver calls
+request_irq(), because an MSI is delivered via a vector that is
+different from the vector of a pin-based interrupt.
+
+4.2.2 pci_enable_msi_range
int pci_enable_msi_range(struct pci_dev *dev, int minvec, int maxvec)
@@ -158,7 +170,12 @@
return pci_enable_msi_range(pdev, 1, 1);
}
-4.2.2 pci_disable_msi
+Note, unlike pci_enable_msi() function, which could be also used to
+enable the single MSI mode, pci_enable_msi_range() returns either a
+negative errno or 1 (not negative errno or 0 - as pci_enable_msi()
+does).
+
+4.2.3 pci_disable_msi
void pci_disable_msi(struct pci_dev *dev)
@@ -172,7 +189,7 @@
Failure to do so results in a BUG_ON(), leaving the device with
MSI enabled and thus leaking its vector.
-4.2.3 pci_msi_vec_count
+4.2.4 pci_msi_vec_count
int pci_msi_vec_count(struct pci_dev *dev)