libusb

On Friday 13 May 2005 23:06, ben@... wrote:

> Hi All,
>
> I am having the same problem as Jake Janovetz ...
>
> My setup:
> Fedore Core 3, libusb-0.1.10a (same results with Fedora stock libusb-0.1.8)
>
> dev->descriptor.iSerialNumber == 3
> usb_get_string_simple(,,,) returns -1
>
> testlibusb has the same problem
>

Possible you need root privilegies to do this. Or usbfs must be mounted with 
RW acces for current user.

On 5/13/05, Dmitry Nezhevenko <dionua@...> wrote:
> Possible you need root privilegies to do this. Or usbfs must be mounted w=
ith
> RW acces for current user.

Very likely.

If I recall, usbview uses /proc/bus/usb/devices (not libusb), but that
file only has a couple of string descriptors (Manufacturer, Product
and SerialNumber).

--=20
- Charles Lepple

On Saturday 14 May 2005 00:47, Charles Lepple wrote:

> On 5/13/05, Dmitry Nezhevenko <dionua@...> wrote:
> > Possible you need root privilegies to do this. Or usbfs must be mounted
> > with RW acces for current user.
>
> Very likely.
>
> If I recall, usbview uses /proc/bus/usb/devices (not libusb), but that
> file only has a couple of string descriptors (Manufacturer, Product
> and SerialNumber).

I don't know about usbview, but sample in libusb use libusb. Also if you try 
to modify sample's code (add usb_strerror() calls), you get error like 
"Operation is not permitted"

On 5/13/05, Dmitry Nezhevenko <dionua@...> wrote:
> On Saturday 14 May 2005 00:47, Charles Lepple wrote:
>=20
> > On 5/13/05, Dmitry Nezhevenko <dionua@...> wrote:
> > > Possible you need root privilegies to do this. Or usbfs must be mount=
ed
> > > with RW acces for current user.
> >
> > Very likely.
> >
> > If I recall, usbview uses /proc/bus/usb/devices (not libusb), but that
> > file only has a couple of string descriptors (Manufacturer, Product
> > and SerialNumber).
>=20
> I don't know about usbview, but sample in libusb use libusb. Also if you =
try
> to modify sample's code (add usb_strerror() calls), you get error like
> "Operation is not permitted"

So have you tried changing permissions on the /proc/bus/usb/???/???
nodes, or running as root?

I confirmed that the reason why usbview would work (when libusb-based
solutions would not, possibly due to permission problems) is that
usbview is indeed reading /proc/bus/usb/devices. Since this is a text
file, you do not need anything more than read permission. However, to
send arbitrary control messages to a device (including the ones to get
string descriptors), you need read+write permissions.

--=20
- Charles Lepple