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    Subject[PATCH 2/7] staging: fsl_-mc: add device binding path 'driver_override'
    Date
    From: Bharat Bhushan <bharat.bhushan@freescale.com>

    This patch is required for vfio-fsl-mc meta driver to successfully bind
    layerscape container devices for device passthrough. This patch adds
    a mechanism to allow a layerscape device to specify a driver rather than
    a layerscape driver provide a device match.

    This patch is based on following proposed patches for PCI and platform devices
    - https://lkml.org/lkml/2014/4/8/571 :- For Platform devices
    - http://lists-archives.com/linux-kernel/28030441-pci-introduce-new-device-binding-path-using-pci_dev-driver_override.html :- For PCI devices

    Example to allow a device (dprc.1) to specifically bind
    with driver (vfio-fsl-mc):-
    - echo vfio-fsl-mc > /sys/bus/fsl-mc/devices/dprc.1/driver_override
    - echo dprc.1 > /sys/bus/fsl-mc/drivers/fsl_mc_dprc/unbind
    - echo dprc.1 > /sys/bus/fsl-mc/drivers/vfio-fsl-mc/bind

    Signed-off-by: J. German Rivera <German.Rivera@freescale.com>
    Change-Id: I11303bfe0196540e931dd2108a8b957dd45ae083
    Reviewed-on: http://git.am.freescale.net:8181/34235
    Reviewed-by: Stuart Yoder <stuart.yoder@freescale.com>
    Tested-by: Stuart Yoder <stuart.yoder@freescale.com>
    ---
    drivers/staging/fsl-mc/bus/mc-bus.c | 67 +++++++++++++++++++++++++++++++++++++
    drivers/staging/fsl-mc/include/mc.h | 2 ++
    2 files changed, 69 insertions(+)

    diff --git a/drivers/staging/fsl-mc/bus/mc-bus.c b/drivers/staging/fsl-mc/bus/mc-bus.c
    index 7332b26..a419c2f 100644
    --- a/drivers/staging/fsl-mc/bus/mc-bus.c
    +++ b/drivers/staging/fsl-mc/bus/mc-bus.c
    @@ -58,6 +58,12 @@ static int fsl_mc_bus_match(struct device *dev, struct device_driver *drv)
    if (WARN_ON(!fsl_mc_bus_type.dev_root))
    goto out;

    + /* When driver_override is set, only bind to the matching driver */
    + if (mc_dev->driver_override) {
    + found = !strcmp(mc_dev->driver_override, mc_drv->driver.name);
    + goto out;
    + }
    +
    if (!mc_drv->match_id_table)
    goto out;

    @@ -116,10 +122,69 @@ static int fsl_mc_bus_uevent(struct device *dev, struct kobj_uevent_env *env)
    return 0;
    }

    +static ssize_t driver_override_store(struct device *dev,
    + struct device_attribute *attr,
    + const char *buf, size_t count)
    +{
    + struct fsl_mc_device *mc_dev = to_fsl_mc_device(dev);
    + const char *driver_override, *old = mc_dev->driver_override;
    + char *cp;
    +
    + if (WARN_ON(dev->bus != &fsl_mc_bus_type))
    + return -EINVAL;
    +
    + if (count > PATH_MAX)
    + return -EINVAL;
    +
    + driver_override = kstrndup(buf, count, GFP_KERNEL);
    + if (!driver_override)
    + return -ENOMEM;
    +
    + cp = strchr(driver_override, '\n');
    + if (cp)
    + *cp = '\0';
    +
    + if (strlen(driver_override)) {
    + mc_dev->driver_override = driver_override;
    + } else {
    + kfree(driver_override);
    + mc_dev->driver_override = NULL;
    + }
    +
    + kfree(old);
    +
    + return count;
    +}
    +
    +static ssize_t driver_override_show(struct device *dev,
    + struct device_attribute *attr, char *buf)
    +{
    + struct fsl_mc_device *mc_dev = to_fsl_mc_device(dev);
    +
    + return sprintf(buf, "%s\n", mc_dev->driver_override);
    +}
    +
    +static DEVICE_ATTR_RW(driver_override);
    +
    +static struct attribute *fsl_mc_dev_attrs[] = {
    + &dev_attr_driver_override.attr,
    + NULL,
    +};
    +
    +static const struct attribute_group fsl_mc_dev_group = {
    + .attrs = fsl_mc_dev_attrs,
    +};
    +
    +static const struct attribute_group *fsl_mc_dev_groups[] = {
    + &fsl_mc_dev_group,
    + NULL,
    +};
    +
    struct bus_type fsl_mc_bus_type = {
    .name = "fsl-mc",
    .match = fsl_mc_bus_match,
    .uevent = fsl_mc_bus_uevent,
    + .dev_groups = fsl_mc_dev_groups,
    };
    EXPORT_SYMBOL_GPL(fsl_mc_bus_type);

    @@ -499,6 +564,8 @@ void fsl_mc_device_remove(struct fsl_mc_device *mc_dev)
    fsl_mc_bus_type.dev_root = NULL;
    }

    + kfree(mc_dev->driver_override);
    + mc_dev->driver_override = NULL;
    if (mc_bus)
    devm_kfree(mc_dev->dev.parent, mc_bus);
    else
    diff --git a/drivers/staging/fsl-mc/include/mc.h b/drivers/staging/fsl-mc/include/mc.h
    index 531cb8c..f965c4d 100644
    --- a/drivers/staging/fsl-mc/include/mc.h
    +++ b/drivers/staging/fsl-mc/include/mc.h
    @@ -145,6 +145,7 @@ struct fsl_mc_device_irq {
    * @regions: pointer to array of MMIO region entries
    * @irqs: pointer to array of pointers to interrupts allocated to this device
    * @resource: generic resource associated with this MC object device, if any.
    + * @driver_override: Driver name to force a match
    *
    * Generic device object for MC object devices that are "attached" to a
    * MC bus.
    @@ -177,6 +178,7 @@ struct fsl_mc_device {
    struct resource *regions;
    struct fsl_mc_device_irq **irqs;
    struct fsl_mc_resource *resource;
    + const char *driver_override;
    };

    #define to_fsl_mc_device(_dev) \
    --
    2.3.3


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