[PATCH v4 05/10] PCI: Add pci_status_get_and_clear_errors

[Heiner Kallweit <hkallweit1@gmail.com>]

Several drivers use the following code sequence:
1. Read PCI_STATUS
2. Mask out non-error bits
3. Action based on error bits set
4. Write back set error bits to clear them

As this is a repeated pattern, add a helper to the PCI core.

Signed-off-by: Heiner Kallweit <hkallweit1@gmail.com>
---
v4:
- improve commit description
---
 drivers/pci/pci.c   | 23 +++++++++++++++++++++++
 include/linux/pci.h |  1 +
 2 files changed, 24 insertions(+)

diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
index d828ca835..c16b0ba2a 100644
--- a/drivers/pci/pci.c
+++ b/drivers/pci/pci.c
@@ -173,6 +173,29 @@ unsigned char pci_bus_max_busnr(struct pci_bus *bus)
 }
 EXPORT_SYMBOL_GPL(pci_bus_max_busnr);
 
+/**
+ * pci_status_get_and_clear_errors - return and clear error bits in PCI_STATUS
+ * @pdev: the PCI device
+ *
+ * Returns error bits set in PCI_STATUS and clears them.
+ */
+int pci_status_get_and_clear_errors(struct pci_dev *pdev)
+{
+	u16 status;
+	int ret;
+
+	ret = pci_read_config_word(pdev, PCI_STATUS, &status);
+	if (ret != PCIBIOS_SUCCESSFUL)
+		return -EIO;
+
+	status &= PCI_STATUS_ERROR_BITS;
+	if (status)
+		pci_write_config_word(pdev, PCI_STATUS, status);
+
+	return status;
+}
+EXPORT_SYMBOL_GPL(pci_status_get_and_clear_errors);
+
 #ifdef CONFIG_HAS_IOMEM
 void __iomem *pci_ioremap_bar(struct pci_dev *pdev, int bar)
 {
diff --git a/include/linux/pci.h b/include/linux/pci.h
index 101d71e0a..7beaf51e9 100644
--- a/include/linux/pci.h
+++ b/include/linux/pci.h
@@ -1210,6 +1210,7 @@ int pci_select_bars(struct pci_dev *dev, unsigned long flags);
 bool pci_device_is_present(struct pci_dev *pdev);
 void pci_ignore_hotplug(struct pci_dev *dev);
 struct pci_dev *pci_real_dma_dev(struct pci_dev *dev);
+int pci_status_get_and_clear_errors(struct pci_dev *pdev);
 
 int __printf(6, 7) pci_request_irq(struct pci_dev *dev, unsigned int nr,
 		irq_handler_t handler, irq_handler_t thread_fn, void *dev_id,
-- 
2.25.1