From mboxrd@z Thu Jan 1 00:00:00 1970 From: Greg KH Date: Tue, 14 Jun 2005 00:54:03 +0000 Subject: Re: sysfs attribute example Message-Id: <20050614005403.GA17180@kroah.com> List-Id: References: In-Reply-To: MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: linux-hotplug@vger.kernel.org On Mon, Jun 13, 2005 at 06:01:26PM -0500, Stephen Morgan wrote: > > -----Original Message----- > > From: Kay Sievers [mailto:kay.sievers@vrfy.org] > > Sent: Friday, June 10, 2005 11:10 AM > > To: Stephen Morgan > > Cc: linux-hotplug-devel > > Subject: Re: sysfs attribute example > > > > > > On Fri, Jun 10, 2005 at 12:05:07PM -0500, Stephen Morgan wrote: > > > Hello all, > > > > > > Can someone point me to an example of exporting a sysfs attribute from a > > > driver? (Or tell me if I shouldn't.) I'm trying to get a > > value from my USB > > > device driver's probe() into an attribute so my udev .rules > > file can pick it > > > up. > > > > > > I've tried to follow what's in LDD 3rd ed. (page 374) > > "...simply fill in an > > > attribute and pass it to sysfs_create_file()" > > > > > > From my probe() function: > > > > > > mydev->my_attribute.name = "my_attribute_name"; > > > mydev->my_attribute.owner = THIS_MODULE; > > > mydev->my_attribute.mode = S_IRUGO; > > > > > > sysfs_create_file(&(interface->class_dev->kobj), > > &(mydev->my_attribute)); > > > > > > When a device is probed, the file "my_attribute_name" shows up > > in sysfs, but > > > I get a "kernel NULL pointer dereference at virtual address 00000004" > > > (address changes with the USB port I plug into). > > > > > > I'm also not seeing how to attach a value to the attribute. > > So, clearly, > > > I'm missing something crucial here :-) > > > > Sure, you do. :) > > > > Look for: DEVICE_ATTR() in the kernel code. > > > > Good luck, > > Kay > > > > Hi Kay, > > Thanks for your help. > > This has gotten me much closer. However, the show() function seems to be > receiving a pointer to the usb_interface's class_device instead of its > device. Any ideas why? Because that's where you registered the attribute? :) Care to show us your patch? thanks, greg k-h ------------------------------------------------------- This SF.Net email is sponsored by: NEC IT Guy Games. How far can you shotput a projector? How fast can you ride your desk chair down the office luge track? If you want to score the big prize, get to know the little guy. Play to win an NEC 61" plasma display: http://www.necitguy.com/?r _______________________________________________ Linux-hotplug-devel mailing list http://linux-hotplug.sourceforge.net Linux-hotplug-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/linux-hotplug-devel