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, 62 insertions, 0 deletions

diff --git a/Documentation/trace/sys-t.rst b/Documentation/trace/sys-t.rst
new file mode 100644
index 000000000..3d8eb9273
--- /dev/null
+++ b/Documentation/trace/sys-t.rst
@@ -0,0 +1,62 @@
+.. SPDX-License-Identifier: GPL-2.0
+
+===================
+MIPI SyS-T over STP
+===================
+
+The MIPI SyS-T protocol driver can be used with STM class devices to
+generate standardized trace stream. Aside from being a standard, it
+provides better trace source identification and timestamp correlation.
+
+In order to use the MIPI SyS-T protocol driver with your STM device,
+first, you'll need CONFIG_STM_PROTO_SYS_T.
+
+Now, you can select which protocol driver you want to use when you create
+a policy for your STM device, by specifying it in the policy name:
+
+# mkdir /config/stp-policy/dummy_stm.0:p_sys-t.my-policy/
+
+In other words, the policy name format is extended like this:
+
+  <device_name>:<protocol_name>.<policy_name>
+
+With Intel TH, therefore it can look like "0-sth:p_sys-t.my-policy".
+
+If the protocol name is omitted, the STM class will chose whichever
+protocol driver was loaded first.
+
+You can also double check that everything is working as expected by
+
+# cat /config/stp-policy/dummy_stm.0:p_sys-t.my-policy/protocol
+p_sys-t
+
+Now, with the MIPI SyS-T protocol driver, each policy node in the
+configfs gets a few additional attributes, which determine per-source
+parameters specific to the protocol:
+
+# mkdir /config/stp-policy/dummy_stm.0:p_sys-t.my-policy/default
+# ls /config/stp-policy/dummy_stm.0:p_sys-t.my-policy/default
+channels
+clocksync_interval
+do_len
+masters
+ts_interval
+uuid
+
+The most important one here is the "uuid", which determines the UUID
+that will be used to tag all data coming from this source. It is
+automatically generated when a new node is created, but it is likely
+that you would want to change it.
+
+do_len switches on/off the additional "payload length" field in the
+MIPI SyS-T message header. It is off by default as the STP already
+marks message boundaries.
+
+ts_interval and clocksync_interval determine how much time in milliseconds
+can pass before we need to include a protocol (not transport, aka STP)
+timestamp in a message header or send a CLOCKSYNC packet, respectively.
+
+See Documentation/ABI/testing/configfs-stp-policy-p_sys-t for more
+details.
+
+* [1] https://www.mipi.org/specifications/sys-t