Re: [RFC 1/2] USB: Notify OTG errors to user space via uevents

[pkondeti@codeaurora.org]

Hi Greg,

> On Mon, Dec 06, 2010 at 06:07:50PM +0530, Pavankumar Kondeti wrote:
>> OTG specification mandates no silent failures and all errors should
>> be reported to the user.  The spec itself does not give the exact
>> error description. But recommends the error message to be self
>> explanatory.  Provide otg_notify_error() utility for USB core and
>> OTG driver to send the error codes to user space.  All the error
>> code values are described in include/linux/usb/ch9.h.  The user space
>> application can listen to netlink socket and parse the buffer for
>> "MODULE=OTG" and "ERROR=n", where 'n' contains the error code.
>
> How are you going to listen to the netlink socket that is already
> grabbed by libudev?
>
Sorry. I never worked with udev. But I read udev documentation.
I thought an external script can be invoked by adding a udev rule
when MODULE=OTG is matched and ERROR value can be accessed
in the script via env variable.

> Please, if you really want to do this, create your own netlink socket,
> don't create new uevent messages that will just confused the existing
> tools out there, that's ripe for big problems.
>
I have seen examples in drivers  sending uevents for notifying docking
station status (drivers/acpi/dock.c) and when backlight brightness
changes (drivers/video/backlight/backlight.c). So I have taken this
approach.