linux-kernel - Re: [PATCH v10] leds: USB: HID: Add support for MSI GT683R led panels

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Date:	Mon, 23 Jun 2014 21:52:12 +0200
From:	Johan Hovold <johan@...nel.org>
To:	Greg KH <greg@...ah.com>
Cc:	Johan Hovold <johan@...nel.org>,
	Janne Kanniainen <janne.kanniainen@...il.com>, jkosina@...e.cz,
	cooloney@...il.com, linux-kernel@...r.kernel.org,
	linux-leds@...r.kernel.org, linux-usb@...r.kernel.org,
	linux-input@...r.kernel.org
Subject: Re: [PATCH v10] leds: USB: HID: Add support for MSI GT683R led panels

On Mon, Jun 23, 2014 at 03:40:59PM -0400, Greg KH wrote:
> On Mon, Jun 23, 2014 at 09:31:34PM +0200, Johan Hovold wrote:
> > On Mon, Jun 23, 2014 at 02:24:32PM -0400, Greg KH wrote:
> > > On Mon, Jun 23, 2014 at 02:23:24PM -0400, Greg KH wrote:
> > > > On Mon, Jun 23, 2014 at 08:16:48PM +0300, Janne Kanniainen wrote:
> > > > > +	ret = sysfs_create_group(&led->hdev->dev.kobj, &gt683r_attribute_group);
> > > > > +	if (ret) {
> > > > > +		hid_err(hdev, "failed to create sysfs attributes\n");
> > > > > +		goto fail;
> > > > > +	}
> > > > 
> > > > No, you need to set the attribute group _before_ you call
> > > > led_classdev_register, as that is where the device will be created in
> > > > sysfs.  Surely the other led drivers already do this?  I'm almost afraid
> > > > to go look...
> > > 
> > > Yes, they do it already, set .dev_attr_group and you should be fine.
> > 
> > But this isn't an attribute of the LEDs but rather of the parent HID
> > device that is being probed (the led_mode is common to all three LEDs
> > and thus belongs in the parent device, right?).
> 
> Then that's even worse :(
> 
> The sysfs attribute should be on the class device here for the LED, you
> should not put an attribute on a device you are not the driver for.

But this is the driver for the HID device, which then in turn has three
individual LEDs. This particular device isn't really an input device
(the actual keyboard in this case appears to be connected over PS2), but
there are several HID drivers which are primarily input devices with
LEDs as sub-devices (e.g. drivers/hid/hid-lg4ff.c).

Johan
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