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USB 2.0 device through a USB 1.1 hub

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	USB 2.0 device through a USB 1.1 hub by rliou :: Rate this Message: Reply to Author \| View Threaded \| Show Only this Message Some parts of this message have been removed. Learn more about Nabble's security policy. I need to detect if my USB 2.0 device is connected through a USB 1.1 hub so I can handle the device accordingly. The value of bcdUSB in the descriptor and device qualifier always shows me 200H(USB 2.0) with or without the hub. How do I get the actual USB speed for a device with a low/full speed hub in the middle? Thanks. ------------------------------------------------------------------------- This SF.Net email is sponsored by the Moblin Your Move Developer's challenge Build the coolest Linux based applications with Moblin SDK & win great prizes Grand prize is a trip for two to an Open Source event anywhere in the world http://moblin-contest.org/redirect.php?banner_id=100&url=/ _______________________________________________ Libusb-devel mailing list Libusb-devel@... https://lists.sourceforge.net/lists/listinfo/libusb-devel
	Re: USB 2.0 device through a USB 1.1 hub by Alan Stern :: Rate this Message: Reply to Author \| View Threaded \| Show Only this Message On Tue, 21 Oct 2008 rliou@... wrote: > I need to detect if my USB 2.0 device is connected through a USB 1.1 > hub so I can handle the device accordingly. The value of bcdUSB in > the descriptor and device qualifier always shows me 200H(USB 2.0) > with or without the hub. How do I get the actual USB speed for a > device with a low/full speed hub in the middle? I don't think there's any direct way to do it with libusb. You can use an indirect technique. For example, if a device is running at high speed then all Bulk endpoints must have a maxpacket size of 512, whereas at full speed all Bulk endpoints must have a maxpacket size <= 64. Or you could parse the contents of /proc/bus/usb/devices if you're running on a Linux system. That file contains the actual speed of each USB device (among a lot of other information). Or you can get the speed through sysfs. Alan Stern ------------------------------------------------------------------------- This SF.Net email is sponsored by the Moblin Your Move Developer's challenge Build the coolest Linux based applications with Moblin SDK & win great prizes Grand prize is a trip for two to an Open Source event anywhere in the world http://moblin-contest.org/redirect.php?banner_id=100&url=/ _______________________________________________ Libusb-devel mailing list Libusb-devel@... https://lists.sourceforge.net/lists/listinfo/libusb-devel
	Re: USB 2.0 device through a USB 1.1 hub by Tim Roberts :: Rate this Message: Reply to Author \| View Threaded \| Show Only this Message rliou@... wrote: > > I need to detect if my USB 2.0 device is connected through a USB 1.1 > hub so I can handle the device accordingly. The value of bcdUSB in the > descriptor and device qualifier always shows me 200H(USB 2.0) with or > without the hub. How do I get the actual USB speed for a device with a > low/full speed hub in the middle? > Do you have an "other speed configuration descriptor"? If so, you should be able to fetch the current configuration descriptor and see which one you got. Your device should return the "other speed" descriptor if it connects as USB 1.1. -- Tim Roberts, timr@... Providenza & Boekelheide, Inc. ------------------------------------------------------------------------- This SF.Net email is sponsored by the Moblin Your Move Developer's challenge Build the coolest Linux based applications with Moblin SDK & win great prizes Grand prize is a trip for two to an Open Source event anywhere in the world http://moblin-contest.org/redirect.php?banner_id=100&url=/ _______________________________________________ Libusb-devel mailing list Libusb-devel@... https://lists.sourceforge.net/lists/listinfo/libusb-devel
	Re: USB 2.0 device through a USB 1.1 hub by Alan Stern :: Rate this Message: Reply to Author \| View Threaded \| Show Only this Message On Wed, 22 Oct 2008, Tim Roberts wrote: > rliou@... wrote: > > > > I need to detect if my USB 2.0 device is connected through a USB 1.1 > > hub so I can handle the device accordingly. The value of bcdUSB in the > > descriptor and device qualifier always shows me 200H(USB 2.0) with or > > without the hub. How do I get the actual USB speed for a device with a > > low/full speed hub in the middle? > > > > Do you have an "other speed configuration descriptor"? If so, you > should be able to fetch the current configuration descriptor and see > which one you got. Your device should return the "other speed" > descriptor if it connects as USB 1.1. A USB 2.0 device will _never_ connect as USB 1.1. No matter what speed it operates at, it will always report its bcdUSB value as 0x0200. This is required by the USB 2.0 spec. Furthermore, you can't rely on the "other speed config" descriptor to tell you what speed a USB 2.0 device is running at. If it's running at full speed then the "other speed config" descriptor will be for a high-speed configuration, and vice versa, if it's running at high speed then the "other speed config" descriptor will be for a full-speed configuration. Either way, you still have to figure out which configuration is for which speed. There's no direct way to do this, since the speed isn't part of the config descriptor. Alan Stern ------------------------------------------------------------------------- This SF.Net email is sponsored by the Moblin Your Move Developer's challenge Build the coolest Linux based applications with Moblin SDK & win great prizes Grand prize is a trip for two to an Open Source event anywhere in the world http://moblin-contest.org/redirect.php?banner_id=100&url=/ _______________________________________________ Libusb-devel mailing list Libusb-devel@... https://lists.sourceforge.net/lists/listinfo/libusb-devel
	Re: USB 2.0 device through a USB 1.1 hub by Tim Roberts :: Rate this Message: Reply to Author \| View Threaded \| Show Only this Message Alan Stern wrote: > On Wed, 22 Oct 2008, Tim Roberts wrote: > > >> Do you have an "other speed configuration descriptor"? If so, you >> should be able to fetch the current configuration descriptor and see >> which one you got. Your device should return the "other speed" >> descriptor if it connects as USB 1.1. >> > > A USB 2.0 device will _never_ connect as USB 1.1. No matter what speed > it operates at, it will always report its bcdUSB value as 0x0200. This > is required by the USB 2.0 spec. > You are quite correct. I should have said "...if it is forced to connect as full-speed." > Furthermore, you can't rely on the "other speed config" descriptor to > tell you what speed a USB 2.0 device is running at. If it's running at > full speed then the "other speed config" descriptor will be for a > high-speed configuration, and vice versa, if it's running at high speed > then the "other speed config" descriptor will be for a full-speed > configuration. > But that's clearly sufficient. As long as you can tell the difference between them, you just ask for the current configuration descriptor. If the one you get is your high-speed descriptor, then you are running high-speed. If the one you get is your full-speed descriptor, then you are running full-speed. This doesn't work in the general case for an arbitrary device, but few of us are really writing apps for the general case. -- Tim Roberts, timr@... Providenza & Boekelheide, Inc. ------------------------------------------------------------------------- This SF.Net email is sponsored by the Moblin Your Move Developer's challenge Build the coolest Linux based applications with Moblin SDK & win great prizes Grand prize is a trip for two to an Open Source event anywhere in the world http://moblin-contest.org/redirect.php?banner_id=100&url=/ _______________________________________________ Libusb-devel mailing list Libusb-devel@... https://lists.sourceforge.net/lists/listinfo/libusb-devel
	Re: USB 2.0 device through a USB 1.1 hub by Alan Stern :: Rate this Message: Reply to Author \| View Threaded \| Show Only this Message On Wed, 22 Oct 2008, Tim Roberts wrote: > > Furthermore, you can't rely on the "other speed config" descriptor to > > tell you what speed a USB 2.0 device is running at. If it's running at > > full speed then the "other speed config" descriptor will be for a > > high-speed configuration, and vice versa, if it's running at high speed > > then the "other speed config" descriptor will be for a full-speed > > configuration. > > > > But that's clearly sufficient. As long as you can tell the difference > between them, you just ask for the current configuration descriptor. If > the one you get is your high-speed descriptor, then you are running > high-speed. If the one you get is your full-speed descriptor, then you > are running full-speed. If you can tell the difference then you don't need to use the "other speed config" descriptor at all. The real question is how can you tell the difference? It depends on the device, obviously, but in general full-speed and high-speed configs tend to be pretty similar. The most notable distinction, as I pointed out earlier, is the size of the Bulk endpoint maxpacket values. However, if somebody is concerned with only one specific device, things become simpler. Compare the two descriptors for the two difference speeds, looking for any distinguishing characteristic. Then use that characteristic to tell which speed the current config descriptor is for. Alan Stern ------------------------------------------------------------------------- This SF.Net email is sponsored by the Moblin Your Move Developer's challenge Build the coolest Linux based applications with Moblin SDK & win great prizes Grand prize is a trip for two to an Open Source event anywhere in the world http://moblin-contest.org/redirect.php?banner_id=100&url=/ _______________________________________________ Libusb-devel mailing list Libusb-devel@... https://lists.sourceforge.net/lists/listinfo/libusb-devel