Commit 2d7bc010 authored by Logan Gunthorpe's avatar Logan Gunthorpe Committed by Bjorn Helgaas
Browse files

PCI/P2PDMA: Introduce configfs/sysfs enable attribute helpers 



Users of the P2PDMA infrastructure will typically need a way for the user
to tell the kernel to use P2P resources.  Typically this will be a simple
on/off boolean operation but sometimes it may be desirable for the user to
specify the exact device to use for the P2P operation.

Add new helpers for attributes which take a boolean or a PCI device.  Any
boolean as accepted by strtobool() turn P2P on or off (such as 'y', 'n',
'1', '0', etc).  Specifying a full PCI device name/BDF will select the
specific device.

Signed-off-by: default avatarLogan Gunthorpe <logang@deltatee.com>
Signed-off-by: default avatarBjorn Helgaas <bhelgaas@google.com>
Reviewed-by: default avatarChristoph Hellwig <hch@lst.de>
parent 977196b8

drivers/pci/p2pdma.c

+82 −0
Original line number Diff line number Diff line
@@ -8,6 +8,8 @@ 
 * Copyright (c) 2018, Eideticom Inc.

 */



#define pr_fmt(fmt) "pci-p2pdma: " fmt

#include <linux/ctype.h>

#include <linux/pci-p2pdma.h>

#include <linux/module.h>

#include <linux/slab.h>
@@ -721,3 +723,83 @@ int pci_p2pdma_map_sg(struct device *dev, struct scatterlist *sg, int nents, 
	return nents;

}

EXPORT_SYMBOL_GPL(pci_p2pdma_map_sg);



/**

 * pci_p2pdma_enable_store - parse a configfs/sysfs attribute store

 *		to enable p2pdma

 * @page: contents of the value to be stored

 * @p2p_dev: returns the PCI device that was selected to be used

 *		(if one was specified in the stored value)

 * @use_p2pdma: returns whether to enable p2pdma or not

 *

 * Parses an attribute value to decide whether to enable p2pdma.

 * The value can select a PCI device (using it's full BDF device

 * name) or a boolean (in any format strtobool() accepts). A false

 * value disables p2pdma, a true value expects the caller

 * to automatically find a compatible device and specifying a PCI device

 * expects the caller to use the specific provider.

 *

 * pci_p2pdma_enable_show() should be used as the show operation for

 * the attribute.

 *

 * Returns 0 on success

 */

int pci_p2pdma_enable_store(const char *page, struct pci_dev **p2p_dev,

			    bool *use_p2pdma)

{

	struct device *dev;



	dev = bus_find_device_by_name(&pci_bus_type, NULL, page);

	if (dev) {

		*use_p2pdma = true;

		*p2p_dev = to_pci_dev(dev);



		if (!pci_has_p2pmem(*p2p_dev)) {

			pci_err(*p2p_dev,

				"PCI device has no peer-to-peer memory: %s\n",

				page);

			pci_dev_put(*p2p_dev);

			return -ENODEV;

		}



		return 0;

	} else if ((page[0] == '0' || page[0] == '1') && !iscntrl(page[1])) {

		/*

		 * If the user enters a PCI device that  doesn't exist

		 * like "0000:01:00.1", we don't want strtobool to think

		 * it's a '0' when it's clearly not what the user wanted.

		 * So we require 0's and 1's to be exactly one character.

		 */

	} else if (!strtobool(page, use_p2pdma)) {

		return 0;

	}



	pr_err("No such PCI device: %.*s\n", (int)strcspn(page, "\n"), page);

	return -ENODEV;

}

EXPORT_SYMBOL_GPL(pci_p2pdma_enable_store);



/**

 * pci_p2pdma_enable_show - show a configfs/sysfs attribute indicating

 *		whether p2pdma is enabled

 * @page: contents of the stored value

 * @p2p_dev: the selected p2p device (NULL if no device is selected)

 * @use_p2pdma: whether p2pdme has been enabled

 *

 * Attributes that use pci_p2pdma_enable_store() should use this function

 * to show the value of the attribute.

 *

 * Returns 0 on success

 */

ssize_t pci_p2pdma_enable_show(char *page, struct pci_dev *p2p_dev,

			       bool use_p2pdma)

{

	if (!use_p2pdma)

		return sprintf(page, "0\n");



	if (!p2p_dev)

		return sprintf(page, "1\n");



	return sprintf(page, "%s\n", pci_name(p2p_dev));

}

EXPORT_SYMBOL_GPL(pci_p2pdma_enable_show);

include/linux/pci-p2pdma.h

+15 −0
Original line number Diff line number Diff line
@@ -32,6 +32,10 @@ void pci_p2pmem_free_sgl(struct pci_dev *pdev, struct scatterlist *sgl); 
void pci_p2pmem_publish(struct pci_dev *pdev, bool publish);

int pci_p2pdma_map_sg(struct device *dev, struct scatterlist *sg, int nents,

		      enum dma_data_direction dir);

int pci_p2pdma_enable_store(const char *page, struct pci_dev **p2p_dev,

			    bool *use_p2pdma);

ssize_t pci_p2pdma_enable_show(char *page, struct pci_dev *p2p_dev,

			       bool use_p2pdma);

#else /* CONFIG_PCI_P2PDMA */

static inline int pci_p2pdma_add_resource(struct pci_dev *pdev, int bar,

		size_t size, u64 offset)
@@ -82,6 +86,17 @@ static inline int pci_p2pdma_map_sg(struct device *dev, 
{

	return 0;

}

static inline int pci_p2pdma_enable_store(const char *page,

		struct pci_dev **p2p_dev, bool *use_p2pdma)

{

	*use_p2pdma = false;

	return 0;

}

static inline ssize_t pci_p2pdma_enable_show(char *page,

		struct pci_dev *p2p_dev, bool use_p2pdma)

{

	return sprintf(page, "none\n");

}

#endif /* CONFIG_PCI_P2PDMA */

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