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, 71 insertions, 0 deletions

diff --git a/Documentation/userspace-api/index.rst b/Documentation/userspace-api/index.rst
new file mode 100644
index 000000000..a68b1bea5
--- /dev/null
+++ b/Documentation/userspace-api/index.rst
@@ -0,0 +1,71 @@
+=====================================
+The Linux kernel user-space API guide
+=====================================
+
+.. _man-pages: https://www.kernel.org/doc/man-pages/
+
+While much of the kernel's user-space API is documented elsewhere
+(particularly in the man-pages_ project), some user-space information can
+also be found in the kernel tree itself.  This manual is intended to be the
+place where this information is gathered.
+
+
+System calls
+============
+
+.. toctree::
+   :maxdepth: 1
+
+   unshare
+   futex2
+   ebpf/index
+   ioctl/index
+   mseal
+   rseq
+
+Security-related interfaces
+===========================
+
+.. toctree::
+   :maxdepth: 1
+
+   no_new_privs
+   seccomp_filter
+   landlock
+   lsm
+   mfd_noexec
+   spec_ctrl
+   tee
+   check_exec
+
+Devices and I/O
+===============
+
+.. toctree::
+   :maxdepth: 1
+
+   accelerators/ocxl
+   dma-buf-heaps
+   dma-buf-alloc-exchange
+   fwctl/index
+   gpio/index
+   iommufd
+   media/index
+   dcdbas
+   vduse
+   isapnp
+
+Everything else
+===============
+
+.. toctree::
+   :maxdepth: 1
+
+   ELF
+   liveupdate
+   netlink/index
+   sysfs-platform_profile
+   vduse
+   futex2
+   perf_ring_buffer
+   ntsync