Sharath wrote:
----- Original Message ----
From: Mandeep Sandhu <mandeep.stinger@xxxxxxxxx>
To: Sharath <sharath_75@xxxxxxxxx>
Cc: kernelnewbies <kernelnewbies@xxxxxxxxxxxx>
Sent: Tuesday, April 18, 2006 5:20:51 PM
Subject: Re: controlling LED's on USB flash drives
On 4/18/06, Sharath <sharath_75@xxxxxxxxx> wrote:
Hi Mandeep,
----- Original Message ----
From: Mandeep Sandhu <mandeep.stinger@xxxxxxxxx>
To: kernelnewbies <kernelnewbies@xxxxxxxxxxxx>
Sent: Tuesday, April 18, 2006 3:52:50 PM
Subject: Re: controlling LED's on USB flash drives
On 4/18/06, Greg KH <greg@xxxxxxxxx> wrote:
On Tue, Apr 18, 2006 at 10:26:05AM +0530, Mandeep Sandhu wrote:
Hi all,
How does one control the behavior of the LED's present on the various usb
flash drives. Is it controlled solely by software or is it like that
the usb host controller
controls the LED's operation. eg: when I write to my flash drive the
the LED blinks.
Is this done via some usb driver or does the usb host controller does
that for us
when we issue a write command to the drive? Is usbled.c under drivers/usb/misc
responsible for controlling this operation? Any pointers are welcome.
No, there is no way to control it, it's up to the device itself.
Well, Greg, the reason I was asking was because I wanted to know if the LED
of my drive could be switched off when I umount it. In windows I noticed that
the LED is switched off when the drive is ready to be unplugged. Is it that they
might be removing power to the drive? Could we acheive a similar result?
This would depend on the electronics of the drive however, the LED status is set by the controller on the USB device. This status is commnunicated to it by the UBS protocol. Whena device is inserted, there are softwrae drivers that control the device and later it is mount onto a location in the filesystem.
The two drivers for the hardware are:
ehci_hcd
uhci_hcd
You're forgetting ohci which is the standard set by compaq i believe.
You're correct. Removing ehci_hcd switched off the LED. I guess
removing this module
must be powering off the device. I'll look into the cleanup code to
confirm this.
Thanks.
The only problem being that modules is used to control the other usb devices - mouse etc nd would cause them to cease functioning..
-Sharath
Not to mention that module unloading can be dangerous...
There is ofcourse an alternative.. the break-the-little-light
alternative,you wont know the difference between on and off in the future.
Sorry for the sarcasm...its been a long day.
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