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Date:   Mon, 19 Feb 2018 16:59:14 +0100
From:   Greg KH <gregkh@linuxfoundation.org>
To:     Richard Leitner <dev@g0hl1n.net>
Cc:     linux-usb@vger.kernel.org, linux-kernel@vger.kernel.org,
        stern@rowland.harvard.edu, linux@roeck-us.net,
        mathias.nyman@linux.intel.com, johan@kernel.org,
        felipe.balbi@linux.intel.com, ekorenevsky@gmail.com,
        peter.chen@nxp.com, drake@endlessm.com, joe@perches.com,
        Richard Leitner <richard.leitner@skidata.com>
Subject: Re: [PATCH] usb: core: introduce per-port over-current counters
Message-ID: <20180219155914.GA23577@kroah.com>
References: <20180219120107.20434-1-dev@g0hl1n.net>
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On Mon, Feb 19, 2018 at 01:01:07PM +0100, Richard Leitner wrote:
> From: Richard Leitner <richard.leitner@skidata.com>
> 
> For some userspace applications information on the number of
> over-current conditions at specific USB hub ports is relevant. Therefore
> introduce a oc_counter in the usb port struct which is exported via
> sysfs.
> 
> Signed-off-by: Richard Leitner <richard.leitner@skidata.com>
> ---
> Tested on an i.MX6DL based board.
> ---
>  drivers/usb/core/hub.c  |  4 +++-
>  drivers/usb/core/hub.h  |  1 +
>  drivers/usb/core/port.c | 10 ++++++++++
>  3 files changed, 14 insertions(+), 1 deletion(-)

When you add/remove/modify a sysfs attribute, you always have to
document in Documentation/ABI/


> 
> diff --git a/drivers/usb/core/hub.c b/drivers/usb/core/hub.c
> index c5c1f6cf3228..448fba1e1827 100644
> --- a/drivers/usb/core/hub.c
> +++ b/drivers/usb/core/hub.c
> @@ -5104,8 +5104,10 @@ static void port_event(struct usb_hub *hub, int port1)
>  
>  	if (portchange & USB_PORT_STAT_C_OVERCURRENT) {
>  		u16 status = 0, unused;
> +		port_dev->oc_count++;
>  
> -		dev_dbg(&port_dev->dev, "over-current change\n");
> +		dev_dbg(&port_dev->dev, "over-current change #%u\n",
> +			port_dev->oc_count);
>  		usb_clear_port_feature(hdev, port1,
>  				USB_PORT_FEAT_C_OVER_CURRENT);
>  		msleep(100);	/* Cool down */
> diff --git a/drivers/usb/core/hub.h b/drivers/usb/core/hub.h
> index 2a700ccc868c..b5cf567bf9e2 100644
> --- a/drivers/usb/core/hub.h
> +++ b/drivers/usb/core/hub.h
> @@ -100,6 +100,7 @@ struct usb_port {
>  	unsigned int is_superspeed:1;
>  	unsigned int usb3_lpm_u1_permit:1;
>  	unsigned int usb3_lpm_u2_permit:1;
> +	unsigned int oc_count;
>  };
>  
>  #define to_usb_port(_dev) \
> diff --git a/drivers/usb/core/port.c b/drivers/usb/core/port.c
> index 1a01e9ad3804..0bfe410eb8a7 100644
> --- a/drivers/usb/core/port.c
> +++ b/drivers/usb/core/port.c
> @@ -41,6 +41,15 @@ static ssize_t connect_type_show(struct device *dev,
>  }
>  static DEVICE_ATTR_RO(connect_type);
>  
> +static ssize_t oc_count_show(struct device *dev, struct device_attribute *attr,
> +			     char *buf)
> +{
> +	struct usb_port *port_dev = to_usb_port(dev);
> +
> +	return sprintf(buf, "%u\n", port_dev->oc_count);
> +}
> +static DEVICE_ATTR_RO(oc_count);

I don't see what userspace can do with this number, as there's not much
it can do with it.

thanks,

greg k-h