Re: How to correctly setup a sysfs class

[Greg KH <greg@kroah.com>]

On Tue, Feb 08, 2005 at 03:05:59PM -0600, Kylene Hall wrote:
> Hello-
> 
> I am trying to create a class in the sysfs filesystem for the tpm device
> driver to use. It was brought to my attention that my first attempts
> were missing a release function and thus causing ugly messages in
> /var/log/messages.  The problem I have is I do not know what I need to
> put in the release function.  The class_simple was recommended to me put
> I don't think it meets my needs.

I think linux-kernel is the best place for this...  But anyway...

> What I'd like to do is that when an application is built on top of this
> driver and needs to know where to find the sysfs files for the device,
> it doesn't have to look on all the different buses in /sys.

But you are using the misc device interface, right?  Why not just use
that class interface?  You have a pointer to the class_device offered to
you in the misc structure that is for you to put sysfs files into the
tree.  Just make sure to clean them up when you are done.

> Today TPMs are pci devices but in the future they could be usb devices
> as well.

Ok, you could hang your files off of the struct device if you want too.
All depends on what you feel comfortable with.

> By createing the tpm class and adding each device to the class the
> device link that is created can be followed to find the necessary
> files.  When using class_simple it seems the only file that can be
> created in the class is dev which contains the major and minor number.

No, you have a pointer to the class device that you can then pass to the
"create a class device file" function, right?  That's why you are passed
back a pointer.

> There is no link to the actual device created and since you don't have
> access to the actual struct class you can't create the link either.
> Please direct me if there is another way to do this.

See above.

thanks,

greg k-h


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