[PATCH v2 02/11] PCI: Add the pci_get_class_masked() helper

[Sui Jingfeng <sui.jingfeng@linux.dev>]

From: Sui Jingfeng <suijingfeng@loongson.cn>

Because there is no good way to get the mask member used to searching for
devices that conform to a specific PCI class code, an application needs to
process all PCI display devices can achieve its goal as follows:

pdev = NULL;
do {
	pdev = pci_get_class_masked(PCI_BASE_CLASS_DISPLAY << 16, 0xFF0000, pdev);
	if (pdev)
		do_something_for_pci_display_device(pdev);
} while (pdev);

While previously, we just can not ignore Sub-Class code and the Programming
Interface byte when do the searching.

Signed-off-by: Sui Jingfeng <suijingfeng@loongson.cn>
---
 drivers/pci/search.c | 30 ++++++++++++++++++++++++++++++
 include/linux/pci.h  |  7 +++++++
 2 files changed, 37 insertions(+)

diff --git a/drivers/pci/search.c b/drivers/pci/search.c
index b4c138a6ec02..f1c15aea868b 100644
--- a/drivers/pci/search.c
+++ b/drivers/pci/search.c
@@ -334,6 +334,36 @@ struct pci_dev *pci_get_device(unsigned int vendor, unsigned int device,
 }
 EXPORT_SYMBOL(pci_get_device);
 
+/**
+ * pci_get_class_masked - begin or continue searching for a PCI device by class and mask
+ * @class: search for a PCI device with this class designation
+ * @from: Previous PCI device found in search, or %NULL for new search.
+ *
+ * Iterates through the list of known PCI devices.  If a PCI device is
+ * found with a matching @class, the reference count to the device is
+ * incremented and a pointer to its device structure is returned.
+ * Otherwise, %NULL is returned.
+ * A new search is initiated by passing %NULL as the @from argument.
+ * Otherwise if @from is not %NULL, searches continue from next device
+ * on the global list.  The reference count for @from is always decremented
+ * if it is not %NULL.
+ */
+struct pci_dev *pci_get_class_masked(unsigned int class, unsigned int mask,
+				     struct pci_dev *from)
+{
+	struct pci_device_id id = {
+		.vendor = PCI_ANY_ID,
+		.device = PCI_ANY_ID,
+		.subvendor = PCI_ANY_ID,
+		.subdevice = PCI_ANY_ID,
+		.class_mask = mask,
+		.class = class,
+	};
+
+	return pci_get_dev_by_id(&id, from);
+}
+EXPORT_SYMBOL(pci_get_class_masked);
+
 /**
  * pci_get_class - begin or continue searching for a PCI device by class
  * @class: search for a PCI device with this class designation
diff --git a/include/linux/pci.h b/include/linux/pci.h
index 0ff7500772e6..b20e7ba844bf 100644
--- a/include/linux/pci.h
+++ b/include/linux/pci.h
@@ -1180,6 +1180,9 @@ struct pci_dev *pci_get_slot(struct pci_bus *bus, unsigned int devfn);
 struct pci_dev *pci_get_domain_bus_and_slot(int domain, unsigned int bus,
 					    unsigned int devfn);
 struct pci_dev *pci_get_class(unsigned int class, struct pci_dev *from);
+struct pci_dev *pci_get_class_masked(unsigned int class, unsigned int mask,
+				     struct pci_dev *from);
+
 int pci_dev_present(const struct pci_device_id *ids);
 
 int pci_bus_read_config_byte(struct pci_bus *bus, unsigned int devfn,
@@ -1895,6 +1898,10 @@ static inline struct pci_dev *pci_get_class(unsigned int class,
 					    struct pci_dev *from)
 { return NULL; }
 
+static inline struct pci_dev *pci_get_class_masked(unsigned int class,
+						   unsigned int mask,
+						   struct pci_dev *from)
+{ return NULL; }
 
 static inline int pci_dev_present(const struct pci_device_id *ids)
 { return 0; }
-- 
2.34.1