Re: number of /dev/usb nodes
- From: Chuck Robey <chuckr@xxxxxxxxxxx>
- Date: Sun, 08 Jun 2008 12:52:59 -0400
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Bernd Walter wrote:
On Sun, Jun 08, 2008 at 10:16:26AM -0400, Chuck Robey wrote:
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Bernd Walter wrote:
On Sat, Jun 07, 2008 at 01:18:41PM -0400, Chuck Robey wrote:I was trying to find a good way to do scanning, whjen I create the files like
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I can't seem to find how many /dev/usbN bus devices there can be. I'm writing
some code that scans them all looking for anything that has my device, but I
while I know to start at usb0, just how high do I go? There seem to be 128
device minors, is that the number? (from dev/usb/usb.h)
I can't see any definition of 128 in usb.h that limits the number of
busses.
The major/minor differenciation is long time ago.
You must be looking at old code.
/dev/usb0, how far to go in my loop? Does the lowest available device always
get created? That would imply that as soon as I began to get "No such device"
errors, I could stop iterating. If the rules for picking device filenames are
pretty loose, then I could (for instance) stop scanning, say, 4 numbers past the
first "No such device" returnee.
This wouldn't work if a USB controller is remove - e.g. a pulling a
cardbus card.
Any idea on this? I didn't see this i nthe code, but I just need some sane
limit on what filenames to scan about in. I look for item info, and if the usb
vendor and prodict look friendly, I just snag the filename involved, and use
that. Like, a scan of the usb1 bus might yield me a uhid0 which might be my
meat, whereupon I coulld drop the usb1 open, and replace it with a uhid0 open.
There's more than 1 place that my devices could show, depending on the user's
kernel devices. I just want to have some sane limit on how many usb buses I
open for my scanning.
I never had to deal with this, since writing a USB driver is simple and
as a driver you get informed for each new device.
No need to scan the busses yourself.
But I would say that the most reliable way is to just scan /dev/ for
usb...
Assumptions .... I never said I was writing a FreeBSD driver... I am writing
what Xorg calls an input driver (Xinput). I could rely on the config file, I
thought I would try to use a scan in case I can't find the dev the user passes
me. I see no reason to write a FreeBSD driver when I can do everything I need
within the uhid driver (at least so far, in my test prog).
There IS one caveat: I've posted to the FreeBSD-USB list that there is a part
of the libusbhid that I can't yet get working. Writing a FreeBSD driver would
allow me to use other available data marshalling code, like what's in the ums
driver. If I can't interest anyone to comment about the libusbhid, I might be
forced down that path, but I don't want to.
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- References:
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- From: Chuck Robey
- Re: number of /dev/usb nodes
- From: Bernd Walter
- Re: number of /dev/usb nodes
- From: Chuck Robey
- Re: number of /dev/usb nodes
- From: Bernd Walter
- number of /dev/usb nodes
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