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, 103 insertions, 0 deletions

diff --git a/Documentation/block/stat.rst b/Documentation/block/stat.rst
new file mode 100644
index 000000000..a1cd9db20
--- /dev/null
+++ b/Documentation/block/stat.rst
@@ -0,0 +1,103 @@
+===============================================
+Block layer statistics in /sys/block/<dev>/stat
+===============================================
+
+This file documents the contents of the /sys/block/<dev>/stat file.
+
+The stat file provides several statistics about the state of block
+device <dev>.
+
+Q.
+   Why are there multiple statistics in a single file?  Doesn't sysfs
+   normally contain a single value per file?
+
+A.
+   By having a single file, the kernel can guarantee that the statistics
+   represent a consistent snapshot of the state of the device.  If the
+   statistics were exported as multiple files containing one statistic
+   each, it would be impossible to guarantee that a set of readings
+   represent a single point in time.
+
+The stat file consists of a single line of text containing 17 decimal
+values separated by whitespace.  The fields are summarized in the
+following table, and described in more detail below.
+
+
+=============== ============= =================================================
+Name            units         description
+=============== ============= =================================================
+read I/Os       requests      number of read I/Os processed
+read merges     requests      number of read I/Os merged with in-queue I/O
+read sectors    sectors       number of sectors read
+read ticks      milliseconds  total wait time for read requests
+write I/Os      requests      number of write I/Os processed
+write merges    requests      number of write I/Os merged with in-queue I/O
+write sectors   sectors       number of sectors written
+write ticks     milliseconds  total wait time for write requests
+in_flight       requests      number of I/Os currently in flight
+io_ticks        milliseconds  total time this block device has been active
+time_in_queue   milliseconds  total wait time for all requests
+discard I/Os    requests      number of discard I/Os processed
+discard merges  requests      number of discard I/Os merged with in-queue I/O
+discard sectors sectors       number of sectors discarded
+discard ticks   milliseconds  total wait time for discard requests
+flush I/Os      requests      number of flush I/Os processed
+flush ticks     milliseconds  total wait time for flush requests
+=============== ============= =================================================
+
+read I/Os, write I/Os, discard I/0s
+===================================
+
+These values increment when an I/O request completes.
+
+flush I/Os
+==========
+
+These values increment when an flush I/O request completes.
+
+Block layer combines flush requests and executes at most one at a time.
+This counts flush requests executed by disk. Not tracked for partitions.
+
+read merges, write merges, discard merges
+=========================================
+
+These values increment when an I/O request is merged with an
+already-queued I/O request.
+
+read sectors, write sectors, discard_sectors
+============================================
+
+These values count the number of sectors read from, written to, or
+discarded from this block device.  The "sectors" in question are the
+standard UNIX 512-byte sectors, not any device- or filesystem-specific
+block size.  The counters are incremented when the I/O completes.
+
+read ticks, write ticks, discard ticks, flush ticks
+===================================================
+
+These values count the number of milliseconds that I/O requests have
+waited on this block device.  If there are multiple I/O requests waiting,
+these values will increase at a rate greater than 1000/second; for
+example, if 60 read requests wait for an average of 30 ms, the read_ticks
+field will increase by 60*30 = 1800.
+
+in_flight
+=========
+
+This value counts the number of I/O requests that have been issued to
+the device driver but have not yet completed.  It does not include I/O
+requests that are in the queue but not yet issued to the device driver.
+
+io_ticks
+========
+
+This value counts the number of milliseconds during which the device has
+had I/O requests queued.
+
+time_in_queue
+=============
+
+This value counts the number of milliseconds that I/O requests have waited
+on this block device.  If there are multiple I/O requests waiting, this
+value will increase as the product of the number of milliseconds times the
+number of requests waiting (see "read ticks" above for an example).