Re: [Libusb-devel] Darwin: Loosing connection to IOService at fork()

[Nathan H. <hj...@un...>]

On Wed, 18 Dec 2002, Pete Bentley wrote:

> On Wed, Dec 18, 2002 at 12:17:41PM +0100, Beat Birkhofer wrote:
> > I try to get sane/libusb working on OSX.
> > 
> > I get quite far but then the there's a fork() in the sane backend 
> > (plustek) I use and then I loose the connection to the IOService.
> > 
> > Any ideas how to solve this problem? I'm quite clueless.
> 
> I suspect this may be rather tricky to solve...
> 
> On most Unixes, the device_handle t libusb uses to communicate
> with the device is a file handle, which will get inherited
> by the child of a fork() call.
> 
> On OS X, the IOKit functions that are used to implement libusb
> seem to use mach ports for communicating with the kernel rather
> than file handles... I don't know the semantics of ports well,
> but I'm guessing they don't get shared across a fork() call
> (or at least not without a lot of extra work)

From what I understand, you are correct, ports are not shared across fork 
calls. I am not sure what can be done to fix the problem except by using 
threads rather than forks (though, i am not entirely sure that will work 
either).

I am open to suggestions/ideas on how to attack this within libusb so 
developers dont have to change their code.

-nathan