by Greg Kroah-Hartman

[permalink] [raw]

Subject: Re: [PATCH v2 2/7] staging: fsl_-mc: add device binding path 'driver_override'

On Wed, May 06, 2015 at 04:28:23PM -0500, J. German Rivera wrote:
> From: Bharat Bhushan <[email protected]>
>
> 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 <[email protected]>
> Reviewed-by: Stuart Yoder <[email protected]>
> Tested-by: Stuart Yoder <[email protected]>
> ---
> Changes in v2:
> none
>
> 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 d51120a..0e9cba8 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);

Documenation for this new sysfs attribute?

> +
> +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,
> +};

ATTRIBUTE_GROUP()?