[Fwd: Re: USB Key light on/off state depending on mount]

[Hans de Goede]

Casey Dahlin wrote:
> I recently posted on lkml asking about making the light on your USB key 
> shut off when it was not mounted. Some responses came back suggesting 
> this is not difficult. Might we consider this for inclusion in Fedora?
> 
> -Casey Dahlin
> 

This sounds like a great plan, I had a friend of mine complain about the drive 
light not going off after unmount yesterday.

Is anyone already working on a patch? If not I can take a shot, be warned 
though, I'm not familiar with hal's internals.

Regards,

Hans


> -------- Original Message --------
> Subject:     Re: USB Key light on/off state depending on mount
> Date:     Sat, 25 Aug 2007 13:58:06 +0200
> From:     Éric Piel <Eric.Piel at tremplin-utc.net>
> To:     James Bruce <bruce at andrew.cmu.edu>
> CC:     linux-kernel at vger.kernel.org, Casey Dahlin <cjdahlin at ncsu.edu>
> References:     <fa.BwCgwGvTNIOD+KEeBrvP11xCEmw at ifi.uio.no> 
> <46CF6791.8040509 at shaw.ca> <46D00928.1080901 at andrew.cmu.edu>
> 
> 
> 
> 25/08/07 12:49, James Bruce wrote/a écrit:
>> Robert Hancock wrote:
>>> Casey Dahlin wrote:
>>>> Most USB keys nowadays have a small LED somewhere inside of them 
>>>> that lights up when they are plugged in. On a windows box, the key 
>>>> is lit up whenever it is mounted, and as soon as it is unmounted it 
>>>> turns off, giving a handy physical indicator that the key is safe to 
>>>> remove. On linux, the light is simply on whenever the key is plugged 
>>>> in.
>>>>
>>>> Should linux toggle the light depending on mount state? Is it as 
>>>> trivial as it seems or does this reflect some larger issue?
>>>
>>> I think that Windows turns off power to the port when you do the 
>>> "safely remove hardware" on it, or something like that. Mount/unmount 
>>> doesn't really indicate whether the device is in use in Linux, 
>>> though, since it can still be potentially accessed even when the 
>>> device isn't mounted.
>>
>> If there is a way to toggle the power state from userspace, then a 
>> desktop environment or userland tool can emulate the Windows behavior 
>> if that is desired.  A lot of devices can charge via USB now, and this 
>> is actually more convenient on Linux than on Windows (in effect 
>> Windows requires drivers in order to charge something).  However, 
>> having direct control over this is useful.
> Yes, maybe some userspace such as HAL could turn off the usb devices at 
> the same time it's unmounted. Actually that would be rather intuitive 
> way to tell the user the umount is finished. There doesn't seem to be 
> any loss of funcitonality, once it's turned off you can still re-access 
> the device, and it's automatically turned on again (at least on my PC).
> 
> For the record, here is how one can switch off a usb device (as root):
> # cd /sys/bus/usb/devices/usb*/[0-9]-[0-9] (just go to the directory of 
> the device)
> # echo -n 2 > *:1.0/power/state
> # echo -n 2 > power/state
> 
> I use this to turn off my optical mouse when watching movies, but it 
> works fine as well to turn off usb storage devices.
> It can also be turned on with
> # echo -n 0 > power/state
> 
> See you,
> Eric
> -
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