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-rw-r--r--Documentation/ABI/testing/sysfs-bus-pci33
1 files changed, 33 insertions, 0 deletions
diff --git a/Documentation/ABI/testing/sysfs-bus-pci b/Documentation/ABI/testing/sysfs-bus-pci
index 6fc2c2efe8ab..840727fc75dc 100644
--- a/Documentation/ABI/testing/sysfs-bus-pci
+++ b/Documentation/ABI/testing/sysfs-bus-pci
@@ -457,3 +457,36 @@ Description:
The file is writable if the PF is bound to a driver that
implements ->sriov_set_msix_vec_count().
+
+What: /sys/bus/pci/devices/.../resourceN_resize
+Date: September 2022
+Contact: Alex Williamson <alex.williamson@redhat.com>
+Description:
+ These files provide an interface to PCIe Resizable BAR support.
+ A file is created for each BAR resource (N) supported by the
+ PCIe Resizable BAR extended capability of the device. Reading
+ each file exposes the bitmap of available resource sizes:
+
+ # cat resource1_resize
+ 00000000000001c0
+
+ The bitmap represents supported resource sizes for the BAR,
+ where bit0 = 1MB, bit1 = 2MB, bit2 = 4MB, etc. In the above
+ example the device supports 64MB, 128MB, and 256MB BAR sizes.
+
+ When writing the file, the user provides the bit position of
+ the desired resource size, for example:
+
+ # echo 7 > resource1_resize
+
+ This indicates to set the size value corresponding to bit 7,
+ 128MB. The resulting size is 2 ^ (bit# + 20). This definition
+ matches the PCIe specification of this capability.
+
+ In order to make use of resource resizing, all PCI drivers must
+ be unbound from the device and peer devices under the same
+ parent bridge may need to be soft removed. In the case of
+ VGA devices, writing a resize value will remove low level
+ console drivers from the device. Raw users of pci-sysfs
+ resourceN attributes must be terminated prior to resizing.
+ Success of the resizing operation is not guaranteed.