Sunday, 20 April 2008

Accessing older Rio MP3 players as an unprivileged user

By default unknown USB devices seemed to be owned by user root and group root on Ubuntu Gutsy and Hardy. This is inconvenient when the device is an MP3 player that you'd rather access as a normal user.

I still use my Rio S50 flash player regularly. After it has had its space boosted a little with an SD card it's perfect for listening to MP3s of radio programmes and podcasts on because it is small enough that it is easy to keep track of what is on it and the AA battery lasts forever.

Anyway, I use the rioutil tool for downloading content to the player. It uses libusb to talk to the device without requiring a kernel driver.

With Ubuntu Hardy the device nodes that libusb uses seems to have changed which broke my old rules. After a little bit of strace I was able to come up with the following udev rules which I placed in /etc/udev/rules.d/45-rio.rules:
SUBSYSTEM=="usb", ENV{DEVTYPE}=="usb_device", \
SYSFS{idVendor}=="045a", SYSFS{idProduct}=="5006", GROUP="plugdev"
These rules may well work on Gutsy too.

Of course your user must be a member of the plugdev group, or you can specify a different group if you wish.

If you want to make other Rio flash portables work then just repeat the rule specifying all product numbers from 5001 (Rio600) to 500f (Rio Cali).

Friday, 18 April 2008

Cross-compiling boost 1.34.x and 1.35.0

There seem to be lots of people asking how to cross-compile boost and very few answers. One of the better answers works for v1.33.x but breaks with v1.34.0.

After digging around for a while trying to make it work I was finally given the answer by the esteemed Peter Hartley who had managed to cross-compile boost 1.34 as part of his Just The Linux distribution. His solution seems to work for v1.35.0 too.

The trick that had eluded me until that point was to tell both the user-config.jam file and bjam about the cross compiler.

Something like:
echo "using gcc : : nicearch-linux-g++ ;" > user-config.jam
make BJAM_CONFIG="-sGXX=nicearch-linux-g++" install
If, like me, you want to only generate static libraries and support multiple builds in the same tree then you might need a bit more cleverness:
mkdir -p $build $staging
echo "using gcc : : $CXX ;" > $build/user-config.jam
bjam --toolset=gcc -sGXX=$CXX -sGCC=$CC \
--prefix=$staging --build-dir=$build \
--user-config=$build/user-config.jam --without-python \
variant=release link=static threading=multi
This should be relatively easy to turn into a buildroot package file but I'm no longer using buildroot to build boost so I didn't need to.