linux-kernel - Re: [PATCH v4] usb: core: introduce per-port over-current counters

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Date:   Thu, 22 Mar 2018 13:05:43 +0100
From:   Greg KH <gregkh@...uxfoundation.org>
To:     Richard Leitner <dev@...l1n.net>
Cc:     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,
        Richard Leitner <richard.leitner@...data.com>
Subject: Re: [PATCH v4] usb: core: introduce per-port over-current counters

On Tue, Mar 20, 2018 at 11:17:13AM +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.
> 
> In our case we have a series of USB hardware (using the cp210x driver)
> which communicates using a proprietary protocol. These devices sometimes
> trigger an over-current situation on some hubs. In case of such an
> over-current situation the USB devices offer an interface for reducing
> the max used power. As these conditions are quite rare and imply
> performance reductions of the device we don't want to reduce the max
> power always.
> 
> Therefore give user-space applications the possibility to react
> adequately by introducing an over_current_counter in the usb port struct
> which is exported via sysfs.
> 
> Signed-off-by: Richard Leitner <richard.leitner@...data.com>
> ---
> Changes v4:
> 	- reintroduce forgotten Changelog
> Changes v3:
> 	- Improve sysfs file description as recommended by greg k-h
> Changes v2:
> 	- rename oc_count to over_current_count
> 	- add entry to Documentation/ABI
> 	- add detailled description to commit message
> ---
>  Documentation/ABI/testing/sysfs-bus-usb | 10 ++++++++++
>  drivers/usb/core/hub.c                  |  4 +++-
>  drivers/usb/core/hub.h                  |  1 +
>  drivers/usb/core/port.c                 | 10 ++++++++++
>  4 files changed, 24 insertions(+), 1 deletion(-)
> 
> diff --git a/Documentation/ABI/testing/sysfs-bus-usb b/Documentation/ABI/testing/sysfs-bus-usb
> index 0bd731cbb50c..c702c78f24d8 100644
> --- a/Documentation/ABI/testing/sysfs-bus-usb
> +++ b/Documentation/ABI/testing/sysfs-bus-usb
> @@ -189,6 +189,16 @@ Description:
>  		The file will read "hotplug", "wired" and "not used" if the
>  		information is available, and "unknown" otherwise.
>  
> +What:		/sys/bus/usb/devices/.../(hub interface)/portX/over_current_count
> +Date:		February 2018
> +Contact:	Richard Leitner <richard.leitner@...data.com>
> +Description:
> +		Most hubs are able to detect over-current situations on their
> +		ports and report them to the kernel. This attribute is to expose
> +		the number of over-current situation occurred on a specific port
> +		to user space. This file will contain an unsigned 32 bit value
> +		which wraps to 0 after its maximum is reached.
> +
>  What:		/sys/bus/usb/devices/.../(hub interface)/portX/usb3_lpm_permit
>  Date:		November 2015
>  Contact:	Lu Baolu <baolu.lu@...ux.intel.com>
> diff --git a/drivers/usb/core/hub.c b/drivers/usb/core/hub.c
> index c5c1f6cf3228..6f779b518e75 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->over_current_count++;
>  
> -		dev_dbg(&port_dev->dev, "over-current change\n");
> +		dev_dbg(&port_dev->dev, "over-current change #%u\n",
> +			port_dev->over_current_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..78d7f4dad618 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 over_current_count;

This should be 'u32', right?  I'll go edit it by hand...

thanks,

greg k-h