linux-kernel - [PATCH v9 8/8] ABI: sysfs-bus-pci: add documentation for p2pmem allocate

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Date:   Thu, 25 Aug 2022 09:24:25 -0600
From:   Logan Gunthorpe <logang@...tatee.com>
To:     linux-kernel@...r.kernel.org, linux-nvme@...ts.infradead.org,
        linux-block@...r.kernel.org, linux-pci@...r.kernel.org,
        linux-mm@...ck.org
Cc:     Christoph Hellwig <hch@....de>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Dan Williams <dan.j.williams@...el.com>,
        Jason Gunthorpe <jgg@...pe.ca>,
        Christian König <christian.koenig@....com>,
        John Hubbard <jhubbard@...dia.com>,
        Don Dutile <ddutile@...hat.com>,
        Matthew Wilcox <willy@...radead.org>,
        Daniel Vetter <daniel.vetter@...ll.ch>,
        Minturn Dave B <dave.b.minturn@...el.com>,
        Jason Ekstrand <jason@...kstrand.net>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Xiong Jianxin <jianxin.xiong@...el.com>,
        Bjorn Helgaas <helgaas@...nel.org>,
        Ira Weiny <ira.weiny@...el.com>,
        Robin Murphy <robin.murphy@....com>,
        Martin Oliveira <martin.oliveira@...eticom.com>,
        Chaitanya Kulkarni <ckulkarnilinux@...il.com>,
        Ralph Campbell <rcampbell@...dia.com>,
        Stephen Bates <sbates@...thlin.com>,
        Logan Gunthorpe <logang@...tatee.com>
Subject: [PATCH v9 8/8] ABI: sysfs-bus-pci: add documentation for p2pmem allocate

Add documentation for the p2pmem/allocate binary file which allows
for allocating p2pmem buffers in userspace for passing to drivers
that support them. (Currently only O_DIRECT to NVMe devices.)

Signed-off-by: Logan Gunthorpe <logang@...tatee.com>
---
 Documentation/ABI/testing/sysfs-bus-pci | 12 +++++++++++-
 1 file changed, 11 insertions(+), 1 deletion(-)

diff --git a/Documentation/ABI/testing/sysfs-bus-pci b/Documentation/ABI/testing/sysfs-bus-pci
index 6fc2c2efe8ab..dca5e032b4fa 100644
--- a/Documentation/ABI/testing/sysfs-bus-pci
+++ b/Documentation/ABI/testing/sysfs-bus-pci
@@ -171,7 +171,7 @@ Description:
 		binary file containing the Vital Product Data for the
 		device.  It should follow the VPD format defined in
 		PCI Specification 2.1 or 2.2, but users should consider
-		that some devices may have incorrectly formatted data.  
+		that some devices may have incorrectly formatted data.
 		If the underlying VPD has a writable section then the
 		corresponding section of this file will be writable.
 
@@ -407,6 +407,16 @@ Description:
 	        file contains a '1' if the memory has been published for
 		use outside the driver that owns the device.
 
+What:		/sys/bus/pci/devices/.../p2pmem/allocate
+Date:		August 2022
+Contact:	Logan Gunthorpe <logang@...tatee.com>
+Description:
+		Thes attribute allows mapping p2pmem into userspace. For
+		each mmap() call on this file, the kernel will allocate
+		a chunk of Peer-to-Peer memory for use in Peer-to-Peer
+		transactions. This memory can be used in O_DIRECT calls
+		to NVMe backed files for Peer-to-Peer copies.
+
 What:		/sys/bus/pci/devices/.../link/clkpm
 		/sys/bus/pci/devices/.../link/l0s_aspm
 		/sys/bus/pci/devices/.../link/l1_aspm
-- 
2.30.2