[PATCH v1 1/3] PCI: export pci_get_dma_device() helper to other users

[Andy Shevchenko <andriy.shevchenko-VuQAYsv1563Yd54FQh9/CA@public.gmane.org>]

Some chipsets use the function 0 for DMA on other functions of a
multifunctional device. One of the example is Intel EG20T PCH. This is also
applicable to Lynxpoint PCH when LPSS devices are switched to PCI mode.

This patch exports a useful helper to get a device of the DMA. This device is
needed to request a DMA channel from a proper controller.

Signed-off-by: Andy Shevchenko <andriy.shevchenko-VuQAYsv1563Yd54FQh9/CA@public.gmane.org>
---
 drivers/pci/quirks.c | 2 +-
 include/linux/pci.h  | 9 +++++++++
 2 files changed, 10 insertions(+), 1 deletion(-)

diff --git a/drivers/pci/quirks.c b/drivers/pci/quirks.c
index 80c2d01..8352e5b 100644
--- a/drivers/pci/quirks.c
+++ b/drivers/pci/quirks.c
@@ -3517,7 +3517,7 @@ static struct pci_dev *pci_func_0_dma_source(struct pci_dev *dev)
 	if (!PCI_FUNC(dev->devfn))
 		return pci_dev_get(dev);
 
-	return pci_get_slot(dev->bus, PCI_DEVFN(PCI_SLOT(dev->devfn), 0));
+	return pci_get_dma_device(dev);
 }
 
 static const struct pci_dev_dma_source {
diff --git a/include/linux/pci.h b/include/linux/pci.h
index 61978a4..86caab7 100644
--- a/include/linux/pci.h
+++ b/include/linux/pci.h
@@ -1575,6 +1575,15 @@ static inline int pci_dev_specific_acs_enabled(struct pci_dev *dev,
 static inline void pci_dev_specific_enable_acs(struct pci_dev *dev) { }
 #endif
 
+/*
+ * Some chipsets use the function 0 for DMA on other functions of a
+ * multifunctional device.
+ */
+static inline struct pci_dev *pci_get_dma_device(struct pci_dev *dev)
+{
+	return pci_get_slot(dev->bus, PCI_DEVFN(PCI_SLOT(dev->devfn), 0));
+}
+
 void __iomem *pcim_iomap(struct pci_dev *pdev, int bar, unsigned long maxlen);
 void pcim_iounmap(struct pci_dev *pdev, void __iomem *addr);
 void __iomem * const *pcim_iomap_table(struct pci_dev *pdev);
-- 
2.0.1

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