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From: Hans Petter Selasky <hselasky@c2i.net>
To: Alfred Perlstein <alfred@freebsd.org>
Date: Tue, 19 Aug 2008 22:28:36 +0200
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Cc: freebsd-usb@freebsd.org
Subject: Re: usb4bsd patch review [was Re: ...]
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> >
> > What do the newbus guys say about this?  Adding a workaround in
> > underlying code for a problem caused by your own code is often a signal
> > that you're not going about it the right way.  At the very least the
> > reason for the special case should be documented here.
>
> I need to think about this, Hans gave me a better argument on
> AIM earlier for it, I need to reload this in my head.
>
> > >int
> > >device_delete_all_children(device_t dev)
> > >{
> > >        device_t *devlist;
> > >        int devcount;
> > >        int error;
> > >
> > >        error = device_get_children(dev, &devlist, &devcount);
> > >        if (error == 0) {
> > >                while (devcount-- > 0) {
> > >                        error = device_delete_child(dev,
> > >                        devlist[devcount]);
> > >                        if (error) {
> > >                                break;
> > >                        }
> > >                }
> > >                free(devlist, M_TEMP);
> > >        }
> > >        return (error);
> > >}
> > >

In the existing kernel code, "device_get_children()" is used many places 
without checking the error code. I have patches, but they are not part of the 
patch-set.

Also freeing a pointer to zero bytes is not logical. I'm not sure if this is 
allowed in kernel space?

ptr = malloc(0, ... )
free(0);

The device_get_children() could have returned an error if there are no 
children, but again, the existing code does not check this return value.

--HPS