Re: [PATCH v6 7/8] usb: add usb_device_allow_power_off() and usb_device_prevent_power_off() function.

[Greg KH <gregkh-hQyY1W1yCW8ekmWlsbkhG0B+6BGkLq7r@public.gmane.org>]

On Mon, Jan 21, 2013 at 10:18:06PM +0800, Lan Tianyu wrote:
> Some usb devices can't be resumed correctly after power off. This
> patch is to add usb_device_allow_power_off() and usb_device_prevent_power_off()
> for device's driver. Call pm_runtime_get_sync(portdev) to increase port's usage
> count and then port will not be suspended. The device will not be powered off.
> 
> Acked-by: Alan Stern <stern-nwvwT67g6+6dFdvTe/nMLpVzexx5G7lz@public.gmane.org>
> Signed-off-by: Lan Tianyu <tianyu.lan-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org>
> ---
>  drivers/usb/core/port.c |   28 ++++++++++++++++++++++++++++
>  1 file changed, 28 insertions(+)
> 
> diff --git a/drivers/usb/core/port.c b/drivers/usb/core/port.c
> index 0c51d24..0334d91 100644
> --- a/drivers/usb/core/port.c
> +++ b/drivers/usb/core/port.c
> @@ -18,11 +18,39 @@
>  
>  #include <linux/slab.h>
>  #include <linux/pm_qos.h>
> +#include <linux/module.h>
>  
>  #include "hub.h"
>  
>  static const struct attribute_group *port_dev_group[];
>  
> +/**
> + * usb_device_control_power_off - Allow or prohibit power off device.
> + * @udev: target usb device
> + * @allow: choice of allow or prohibit
> + *
> + * Call pm_runtime_get/put_sync(portdev) to allow or prohibit target
> + * usb device to be powered off in the kernel. The operations of setting
> + * true and false should be couple. The default status is allowed.
> + */
> +int usb_device_control_power_off(struct usb_device *udev, bool allow)
> +{
> +	struct usb_port *port_dev;
> +
> +	if (!udev->parent)
> +		return -EINVAL;
> +
> +	port_dev = hdev_to_hub(udev->parent)->ports[udev->portnum - 1];
> +
> +	if (allow)
> +		pm_runtime_put_sync(&port_dev->dev);
> +	else
> +		pm_runtime_get_sync(&port_dev->dev);
> +
> +	return 0;
> +}
> +EXPORT_SYMBOL_GPL(usb_device_control_power_off);

Oh, I don't see any code calling this function, so why did you add it?

Who needs it?  Where is that code?

thanks,

greg k-h
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