Help with simple char device

Help with simple char device

[Luis A. Montes]

Hi there,

I'm trying to write a simple char device driver. I've used as starting
point code that someone posted recently to the list (I can't find the
post now, it was a file called mymod.c). Anyway, I do:

alloc_chrdev_region()
cdev_alloc()
set owner and file operations
kobject_set_name()
cdev_add()
class_simple_create()
class_simple_device_add()

It nicely creates a /dev/ entry, but it then complains:

wait_for_sysfs[5689]: either wait_for_sysfs (udev 042) needs an update
to handle the device '/class/mydevclass/mydev' properly (no device
symlink) or the sysfs-support of your device's driver needs to be fixed,
please report to <linux-hotplug-devel@lists.sourceforge.net>

Any pointers to what else do I need to do?

-- 
Luis A. Montes <luismontes@isp.com>


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Re: Help with simple char device

[Kay Sievers]

On Thu, 2004-12-30 at 21:32 -0800, Luis A. Montes wrote:
> Hi there,
> 
> I'm trying to write a simple char device driver. I've used as starting
> point code that someone posted recently to the list (I can't find the
> post now, it was a file called mymod.c). Anyway, I do:
> 
> alloc_chrdev_region()
> cdev_alloc()
> set owner and file operations
> kobject_set_name()
> cdev_add()
> class_simple_create()
> class_simple_device_add()
> 
> It nicely creates a /dev/ entry, but it then complains:
> 
> wait_for_sysfs[5689]: either wait_for_sysfs (udev 042) needs an update
> to handle the device '/class/mydevclass/mydev' properly (no device
> symlink) or the sysfs-support of your device's driver needs to be fixed,
> please report to <linux-hotplug-devel@lists.sourceforge.net>
> 
> Any pointers to what else do I need to do?

Just upgrade udev to get rid of the message or simply ignore it.

(That's cause udev doesn't know about that class name and the default is
to expect a symlink to the physical device. Newer udev versions will not
print this message and kernel 2.6.10 will carry the information in the
hotplug environment to let udev explicitly know what to wait for.)

Kay



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