PCI: Add pci_irq_type() to query the allocated interrupt typegrafted

Add a helper that returns PCI_IRQ_MSIX, PCI_IRQ_MSI, or PCI_IRQ_INTX
based on the interrupt type the PCI core selected after
pci_alloc_irq_vectors().

Several drivers already open-code this check against pdev->msix_enabled
and pdev->msi_enabled, or even open code this helper [1].

A common helper avoids the duplication and keeps drivers from accessing
the bitfield directly (see also [2]).

Acked-by: Bjorn Helgaas <bhelgaas@google.com>
Tested-by: John Hubbard <jhubbard@nvidia.com>
Link: https://elixir.bootlin.com/linux/v7.1/source/drivers/net/ethernet/aquantia/atlantic/aq_pci_func.c#L196 [1]
Inspired-by: John Hubbard <jhubbard@nvidia.com>
Link: https://lore.kernel.org/all/DKKG2QM3YJYB.Z2H2B2UXJ75N@kernel.org/ [2]
Reviewed-by: Gary Guo <gary@garyguo.net>
Link: https://patch.msgid.link/20260813165234.620555-5-dakr@kernel.org
[ Add missing pci_irq_type() stub for CONFIG_PCI=n. ]
Signed-off-by: Danilo Krummrich <dakr@kernel.org>

1 files changed, 39 insertions, 0 deletions

diff --git a/Documentation/usb/functionfs-desc.rst b/Documentation/usb/functionfs-desc.rst
new file mode 100644
index 000000000..39649774d
--- /dev/null
+++ b/Documentation/usb/functionfs-desc.rst
@@ -0,0 +1,39 @@
+======================
+FunctionFS Descriptors
+======================
+
+Some of the descriptors that can be written to the FFS gadget are
+described below. Device and configuration descriptors are handled
+by the composite gadget and are not written by the user to the
+FFS gadget.
+
+Descriptors are written to the "ep0" file in the FFS gadget
+following the descriptor header.
+
+.. kernel-doc:: include/uapi/linux/usb/functionfs.h
+   :doc: descriptors
+
+Interface Descriptors
+---------------------
+
+Standard USB interface descriptors may be written. The class/subclass of the
+most recent interface descriptor determines what type of class-specific
+descriptors are accepted.
+
+Class-Specific Descriptors
+--------------------------
+
+Class-specific descriptors are accepted only for the class/subclass of the
+most recent interface descriptor. The following are some of the
+class-specific descriptors that are supported.
+
+DFU Functional Descriptor
+~~~~~~~~~~~~~~~~~~~~~~~~~
+
+When the interface class is USB_CLASS_APP_SPEC and the interface subclass
+is USB_SUBCLASS_DFU, a DFU functional descriptor can be provided.
+The DFU functional descriptor is a described in the USB specification for
+Device Firmware Upgrade (DFU), version 1.1 as of this writing.
+
+.. kernel-doc:: include/uapi/linux/usb/functionfs.h
+   :doc: usb_dfu_functional_descriptor