linux-kernel - Re: [PATCH] usb: core: introduce per-port over-current counters

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Date:   Mon, 19 Feb 2018 17:38:56 +0100
From:   Greg KH <gregkh@...uxfoundation.org>
To:     Richard Leitner <richard.leitner@...data.com>
Cc:     Richard Leitner <dev@...l1n.net>, linux-usb@...r.kernel.org,
        linux-kernel@...r.kernel.org, stern@...land.harvard.edu,
        linux@...ck-us.net, mathias.nyman@...ux.intel.com,
        johan@...nel.org, felipe.balbi@...ux.intel.com,
        ekorenevsky@...il.com, peter.chen@....com, drake@...lessm.com,
        joe@...ches.com
Subject: Re: [PATCH] usb: core: introduce per-port over-current counters

On Mon, Feb 19, 2018 at 05:05:34PM +0100, Richard Leitner wrote:
> 
> On 02/19/2018 04:59 PM, Greg KH wrote:
> > On Mon, Feb 19, 2018 at 01:01:07PM +0100, Richard Leitner wrote:
> >> From: Richard Leitner <richard.leitner@...data.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@...data.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/
> 
> Ok. Thank you. Seems I missed that, Sorry!
> 
> >>
> >> 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.
> 
> I've answered this question to Felipe already:

<snip>

It's not described in the patch changelog, which is where it is required
:)

thanks,

greg k-h