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, 104 insertions, 0 deletions

diff --git a/Documentation/input/userio.rst b/Documentation/input/userio.rst
new file mode 100644
index 000000000..7aaaa629b
--- /dev/null
+++ b/Documentation/input/userio.rst
@@ -0,0 +1,104 @@
+.. include:: <isonum.txt>
+
+===================
+The userio Protocol
+===================
+
+
+:Copyright: |copy| 2015 Lyude Paul <thatslyude@gmail.com>
+
+Sponsored by Red Hat
+
+
+Introduction
+=============
+
+This module is intended to try to make the lives of input driver developers
+easier by allowing them to test various serio devices (mainly the various
+touchpads found on laptops) without having to have the physical device in front
+of them. userio accomplishes this by allowing any privileged userspace program
+to directly interact with the kernel's serio driver and control a virtual serio
+port from there.
+
+Usage overview
+==============
+
+In order to interact with the userio kernel module, one simply opens the
+/dev/userio character device in their applications. Commands are sent to the
+kernel module by writing to the device, and any data received from the serio
+driver is read as-is from the /dev/userio device. All of the structures and
+macros you need to interact with the device are defined in <linux/userio.h> and
+<linux/serio.h>.
+
+Command Structure
+=================
+
+The struct used for sending commands to /dev/userio is as follows::
+
+	struct userio_cmd {
+		__u8 type;
+		__u8 data;
+	};
+
+``type`` describes the type of command that is being sent. This can be any one
+of the USERIO_CMD macros defined in <linux/userio.h>. ``data`` is the argument
+that goes along with the command. In the event that the command doesn't have an
+argument, this field can be left untouched and will be ignored by the kernel.
+Each command should be sent by writing the struct directly to the character
+device. In the event that the command you send is invalid, an error will be
+returned by the character device and a more descriptive error will be printed
+to the kernel log. Only one command can be sent at a time, any additional data
+written to the character device after the initial command will be ignored.
+
+To close the virtual serio port, just close /dev/userio.
+
+Commands
+========
+
+USERIO_CMD_REGISTER
+~~~~~~~~~~~~~~~~~~~
+
+Registers the port with the serio driver and begins transmitting data back and
+forth. Registration can only be performed once a port type is set with
+USERIO_CMD_SET_PORT_TYPE. Has no argument.
+
+USERIO_CMD_SET_PORT_TYPE
+~~~~~~~~~~~~~~~~~~~~~~~~
+
+Sets the type of port we're emulating, where ``data`` is the port type being
+set. Can be any of the serio type macros from <linux/serio.h>. For example:
+SERIO_8042 would set the port type to be a normal PS/2 port.
+
+USERIO_CMD_SET_PORT_PROTO
+~~~~~~~~~~~~~~~~~~~~~~~~~
+
+Sets the protocol of port we're emulating, where ``data`` is the protocol being
+set. Can be any of the serio proto macros from <linux/serio.h>. For example:
+SERIO_IFORCE would set the port type to be an I-Force serial joystick.
+
+USERIO_CMD_SET_PORT_ID
+~~~~~~~~~~~~~~~~~~~~~~
+
+Sets the ``id`` value on the identification of port we're emulating, where
+``data`` is the value being set.
+
+USERIO_CMD_SET_PORT_EXTRA
+~~~~~~~~~~~~~~~~~~~~~~~~~
+
+Sets the ``extra`` value on the identification of port we're emulating, where
+``data`` is the value being set.
+
+USERIO_CMD_SEND_INTERRUPT
+~~~~~~~~~~~~~~~~~~~~~~~~~
+
+Sends an interrupt through the virtual serio port to the serio driver, where
+``data`` is the interrupt data being sent.
+
+Userspace tools
+===============
+
+The userio userspace tools are able to record PS/2 devices using some of the
+debugging information from i8042, and play back the devices on /dev/userio. The
+latest version of these tools can be found at:
+
+	https://github.com/Lyude/ps2emu