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, 116 insertions, 0 deletions

diff --git a/Documentation/userspace-api/gpio/chardev.rst b/Documentation/userspace-api/gpio/chardev.rst
new file mode 100644
index 000000000..c58dd9771
--- /dev/null
+++ b/Documentation/userspace-api/gpio/chardev.rst
@@ -0,0 +1,116 @@
+.. SPDX-License-Identifier: GPL-2.0
+
+===================================
+GPIO Character Device Userspace API
+===================================
+
+This is latest version (v2) of the character device API, as defined in
+``include/uapi/linux/gpio.h.``
+
+First added in 5.10.
+
+.. note::
+   Do NOT abuse userspace APIs to control hardware that has proper kernel
+   drivers. There may already be a driver for your use case, and an existing
+   kernel driver is sure to provide a superior solution to bitbashing
+   from userspace.
+
+   Read Documentation/driver-api/gpio/drivers-on-gpio.rst to avoid reinventing
+   kernel wheels in userspace.
+
+   Similarly, for multi-function lines there may be other subsystems, such as
+   Documentation/spi/index.rst, Documentation/i2c/index.rst,
+   Documentation/driver-api/pwm.rst, Documentation/w1/index.rst etc, that
+   provide suitable drivers and APIs for your hardware.
+
+Basic examples using the character device API can be found in ``tools/gpio/*``.
+
+The API is based around two major objects, the :ref:`gpio-v2-chip` and the
+:ref:`gpio-v2-line-request`.
+
+.. _gpio-v2-chip:
+
+Chip
+====
+
+The Chip represents a single GPIO chip and is exposed to userspace using device
+files of the form ``/dev/gpiochipX``.
+
+Each chip supports a number of GPIO lines,
+:c:type:`chip.lines<gpiochip_info>`. Lines on the chip are identified by an
+``offset`` in the range from 0 to ``chip.lines - 1``, i.e. `[0,chip.lines)`.
+
+Lines are requested from the chip using gpio-v2-get-line-ioctl.rst
+and the resulting line request is used to access the GPIO chip's lines or
+monitor the lines for edge events.
+
+Within this documentation, the file descriptor returned by calling `open()`
+on the GPIO device file is referred to as ``chip_fd``.
+
+Operations
+----------
+
+The following operations may be performed on the chip:
+
+.. toctree::
+   :titlesonly:
+
+   Get Line <gpio-v2-get-line-ioctl>
+   Get Chip Info <gpio-get-chipinfo-ioctl>
+   Get Line Info <gpio-v2-get-lineinfo-ioctl>
+   Watch Line Info <gpio-v2-get-lineinfo-watch-ioctl>
+   Unwatch Line Info <gpio-get-lineinfo-unwatch-ioctl>
+   Read Line Info Changed Events <gpio-v2-lineinfo-changed-read>
+
+.. _gpio-v2-line-request:
+
+Line Request
+============
+
+Line requests are created by gpio-v2-get-line-ioctl.rst and provide
+access to a set of requested lines.  The line request is exposed to userspace
+via the anonymous file descriptor returned in
+:c:type:`request.fd<gpio_v2_line_request>` by gpio-v2-get-line-ioctl.rst.
+
+Within this documentation, the line request file descriptor is referred to
+as ``req_fd``.
+
+Operations
+----------
+
+The following operations may be performed on the line request:
+
+.. toctree::
+   :titlesonly:
+
+   Get Line Values <gpio-v2-line-get-values-ioctl>
+   Set Line Values <gpio-v2-line-set-values-ioctl>
+   Read Line Edge Events <gpio-v2-line-event-read>
+   Reconfigure Lines <gpio-v2-line-set-config-ioctl>
+
+Types
+=====
+
+This section contains the structs and enums that are referenced by the API v2,
+as defined in ``include/uapi/linux/gpio.h``.
+
+.. kernel-doc:: include/uapi/linux/gpio.h
+   :identifiers:
+    gpio_v2_line_attr_id
+    gpio_v2_line_attribute
+    gpio_v2_line_changed_type
+    gpio_v2_line_config
+    gpio_v2_line_config_attribute
+    gpio_v2_line_event
+    gpio_v2_line_event_id
+    gpio_v2_line_flag
+    gpio_v2_line_info
+    gpio_v2_line_info_changed
+    gpio_v2_line_request
+    gpio_v2_line_values
+    gpiochip_info
+
+.. toctree::
+   :hidden:
+
+   error-codes