Re: [Libusb-devel] open by name

[Stephen H. W. <we...@gr...>]

> From: Johannes Erdfelt <joh...@er...>
> Cc: lib...@li...
> Content-Disposition: inline
> Sender: lib...@li...
> X-Original-Date: Sun, 15 Jun 2003 14:49:16 -0400
> Date: Sun, 15 Jun 2003 14:49:16 -0400
> X-UIDL: 9G\d9Ffpd9&ha!!?%]d9
> 
> On Sun, Jun 15, 2003, Andreas Jellinghaus <aj...@du...> wrote:
> > please add a function to open a usb device
> > by device name.
> > 
> > This issue was mentioned earlier by
> > http://sourceforge.net/mailarchive/forum.php?thread_id=1949914&forum_id=5425
> > 
> > However it is not linux specific.
> > on linux the kernel spawns /sbin/hotplug which is some shell
> > magic and in the end it execs e.g. my helper app.
> > On *bsd the usbd can do the same thing.
> > 
> > Paths, environment and all such stuff might be different,
> > but in the end some mechanism detects if there is a new
> > usb device with the product and vendor id i can handle,
> > and it calls my driver, and it can pass the name of the
> > device I need to open.
> > 
> > The current work around is to scan all busses and devices,
> > and compare the filename to the one I already have. that
> > is not useful. please add a direct function 
> > 	usb_dev_handle *usb_open_bypath(char *devpath);
> > 
> > or something similar. accepting a file descriptor would
> > be also ok, if you prefer that.
> > 
> > In case some *bsd does not have an usbd:
> > the fix is to write one / port usbd to that *bsd.
> > That would be the best way to get my driver working
> > on that unix. So if some *bsd does not have an usbd,
> > please still create that function in libusb for all devices.
> > 
> > Thank you!
> > 
> > Regards, Andreas
> > 
> > P.S. If you want me to put my feet where my mouth is, dig into
> > the source, write the patch and submit it: I will do it.
> > It might be very easy for anyone familiar with the source,
> > but take me some time to get into the source...
> > 
> > P.P.S. libusb might also be a good place to document some hints on
> > how to configure hotplug and usbd, so not every author of some
> > hotplugging usb driver app needs to know about it.
> 
> You can already find a device by filename in 0.1. The information needed
> is already available. Look at bus->dirname and dev->filename.
> 
> For 1.0, I will probably add a Linux specific extension (but discourage
> use for everything but integrating with Linux hotplug) to find a device
> based on the usbfs file name.

I concur with this. In Mac OS X, I dont' think there's a reasonable
way to call a user-mode program from the hotplug process. One would
have to write a kernel-mode driver, I think, to make this happen. And
I don't think there's a Unix-style device name; just a multi-digit
"location" code.

-Stephen H. Westin
Any information or opinions in this message are mine: they do not
represent the position of Cornell University or any of its sponsors.