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    Subject[PATCH v5 04/13] 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, or the word 'auto' turn P2P on or off. Specifying a full
    PCI device name/BDF will select the specific device.

    Signed-off-by: Logan Gunthorpe <logang@deltatee.com>
    ---
    drivers/pci/p2pdma.c | 83 ++++++++++++++++++++++++++++++++++++++++++++++
    include/linux/pci-p2pdma.h | 15 +++++++++
    2 files changed, 98 insertions(+)

    diff --git a/drivers/pci/p2pdma.c b/drivers/pci/p2pdma.c
    index 29bd40a87768..3da848f3fe72 100644
    --- a/drivers/pci/p2pdma.c
    +++ b/drivers/pci/p2pdma.c
    @@ -9,6 +9,7 @@
    */

    #define pr_fmt(fmt) "pci-p2pdma: " fmt
    +#include <linux/ctype.h>
    #include <linux/pci-p2pdma.h>
    #include <linux/module.h>
    #include <linux/slab.h>
    @@ -856,3 +857,85 @@ 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 'auto', 'none or a boolean isn't the store 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), a boolean, or 'auto'. 'auto' and a true boolean value
    + * have the same meaning. A false value disables p2pdma and
    + * a PCI device enables it to use a specific device as the
    + * backing 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)) {
    + pr_err("PCI device has no peer-to-peer memory: %s\n",
    + page);
    + pci_dev_put(*p2p_dev);
    + return -ENODEV;
    + }
    +
    + return 0;
    + } else if (sysfs_streq(page, "auto")) {
    + *use_p2pdma = true;
    + 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, "none\n");
    +
    + if (!p2p_dev)
    + return sprintf(page, "auto\n");
    +
    + return sprintf(page, "%s\n", pci_name(p2p_dev));
    +}
    +EXPORT_SYMBOL_GPL(pci_p2pdma_enable_show);
    diff --git a/include/linux/pci-p2pdma.h b/include/linux/pci-p2pdma.h
    index 2f03dbbf5af6..377de4d73767 100644
    --- a/include/linux/pci-p2pdma.h
    +++ b/include/linux/pci-p2pdma.h
    @@ -38,6 +38,10 @@ 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)
    @@ -105,5 +109,16 @@ 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 */
    #endif /* _LINUX_PCI_P2P_H */
    --
    2.11.0
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