Juergen Beisert wrote:
> Arvid Brodin wrote:
>> What's the best way to get a notification in user space when an overcurrent
>> event occurs on a usb port? The idea is to let a user application notify
>> the user that something is wrong.
>
> Long time ago (linux-2.6.36) we did this in one of our projects, to forward
> this event to userland.
>
> From: Juergen Beisert <jbe@xxxxxxxxxxxxxx>
> Date: Wed, 11 Aug 2010 14:18:04 +0200
> Subject: [PATCH] Generate a uevent when an overcurrent event happens
>
> This quick hack generates a 'uevent' to userland and adds the 'POWERFAIL=1'
> environment variable for this report. Any userland program listening to the
> 'uevent' interface can filter for the presence of this environment variable
> to distinguish this special 'uevent' from other 'add' or 'remove' events.
>
> Current disadvantage: Due to the fact, the hub driver tries to enable the
> port again immediately (it does not wait for user interaction) this powerfail
> event gets reported twice: First time when it really happens and second time
> when the external overcurrent detection device will be reset. The second
> false positive report must be sorted out by the userland application.
>
> Signed-off-by: Juergen Beisert <jbe@xxxxxxxxxxxxxx>
> Signed-off-by: Michael Grzeschik <m.grzeschik@xxxxxxxxxxxxxx>
> ---
> drivers/usb/core/hub.c | 4 ++++
> 1 file changed, 4 insertions(+), 0 deletions(-)
>
> diff --git a/drivers/usb/core/hub.c b/drivers/usb/core/hub.c
> index 84c18971..c615292 100644
> --- a/drivers/usb/core/hub.c
> +++ b/drivers/usb/core/hub.c
> @@ -3372,9 +3372,13 @@ static void hub_events(void)
> }
>
> if (portchange & USB_PORT_STAT_C_OVERCURRENT) {
> + char event[] = "POWERFAIL=1";
> + char *envp[] = { event, NULL };
> +
> dev_err (hub_dev,
> "over-current change on port %d\n",
> i);
> + kobject_uevent_env(&hub->intfdev->kobj, KOBJ_CHANGE, envp);
> clear_port_feature(hdev, i,
> USB_PORT_FEAT_C_OVER_CURRENT);
> hub_power_on(hub, true);
>
Thank you, this might be useful!
--
Arvid Brodin
Enea Services Stockholm AB
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