Introducing PodSleuth

PodSleuth is a new project I started last May that aims to probe, identify, and expose properties and metadata bound to iPods. It obsoletes libipoddevice, which had the same goals, but due to many reasons ended up being a mess of spaghetti code and hacks due to effectively being obsoleted overnight about a year ago when Apple made a particular firmware release.

PodSleuth takes the many lessons learned from libipoddevice and evolutions of the iPod itself and implements hardware support in a more future proof, yet backwards compatible and easy to maintain way.

The Technical

The core of its design is platform independent, although PodSleuth in its current and complete form is most usable in the context of HAL. A HAL layer is provided that is used now in Banshee, and we would like to see other certain iPod libraries at least optionally support PodSleuth. This layer is implemented as a HAL callout. Because the callout runs as the same user as the HAL daemon (typically root), it is allowed to cleanly perform operations that were implemented as hacks in libipoddevice (like reading from SCSI code pages).

The metadata that PodSleuth collects is then merged into the HAL device as properties. Once the PodSleuth callout ends, HAL finishes probing the device and exposes the iPod on the Global Device List (GDL) where the mount daemon (i.e. gnome-volume-manager) will then mount the iPod in a manner accessible to the user session. The key here is that by the time the iPod is exposed on the GDL, all PodSleuth properties will have been merged into the device. This makes application and user session library support for PodSleuth properties very easy and straight forward. One need only check for org.podsleuth.version on the device to check if PodSleuth ran against the device. If that property exists, other properties will be available that expose iPod metadata.

if (device.PropertyExists ("org.podsleuth.version")) {
    // We have a PodSleuthed iPod, it's ok to expect 
    // at least the minimum set of properties

    Console.WriteLine (String.Join (", ", device.GetPropertyStringList 
        ("org.podsleuth.ipod.capabilities")));
}

One of the most important changes that affects the end user directly is that the iPod will always be supported based on metadata extracted from the plist file located in the SCSI code pages. This means that even if the iPod is not found in the model table, no functional limitations will be imposed. That is, the model table is now only purely cosmetic (for presenting things like shell color and the right icon). This is in contrast to earlier versions of libipoddevice.

Additionally, PodSleuth sets the info.icon property in HAL which means that once we get new icons for the new iPods and update the existing ones to follow the new required naming specification, the proper iPod icon will finally show up in Nautilus and elsewhere (provided you are running a recent enough GNOME). A cute thing indeed.

The Files

PodSleuth will see its first official release within the next week, alongside a new ipod-sharp release, and Banshee 0.13.2. All of these releases spell out support for new iPods (Classics and Nanos), so stay tuned. PodSleuth is developed in GNOME subversion under the podsleuth module.

The Unfortunately Political

The fun part is that PodSleuth is written in C# of course, a detail that I like to think doesn’t matter, but it certainly and most unfortunately offends many for various reasons. There are two lovely facts that I like to point out when opposition to my language of choice for this project arises:

  • Because PodSleuth is not used as a library, any application written in any language with HAL support can benefit from PodSleuth. I could have written PodSleuth in shell, and it would not affect applications wishing to support it.

    Furthermore, PodSleuth requires only the ECMA approved portions of Mono (which is a 100% open source project and has a strict policy to keep patented code out) and Mono.Posix (which is an open source library wrapping POSIX system calls). Therefore there are no patent concerns (although I know the facts don’t matter to the noisy zealots).

    What matters on the technical side of this point is that most modern distributions ship at least this core subset of Mono these days, so I feel the dependency argument falls apart here as well.

  • My favorite argument against PodSleuth because it is Mono-based comes from the crowd that hates Mono for unfounded political reasons, yet require free software support for their iPod.

    Let’s see, the iPod is closed hardware, proprietary software, contains DRM, supports proprietary formats (doesn’t even have any open format support), and just recently added a hashing mechanism against the primary track database to lock out third party clients. I’m not sure if I’ve ever come across a more proprietary device, yet this zealot crowd has the nerve to scream about Mono!

    This theme is unfortunately all too common in our community (“Oh, it’s OK to run a Mac! Just don’t use Windows! The Mac is shiny too!”).

    In response to this very argument a few days ago in the #banshee IRC channel and mocking what could be seen as a double standard, Jorge Castro quipped,

    “I value freedom so I refuse to use Mono, oh look, a new iPod!”

    So true, so sad. On a somewhat related topic, I recently looked at the APSL next to the Ms-PL. Now that’s funny.

The Bottom Line

There is no reason an application or library focused around iPods shouldn’t support PodSleuth. Regardless of political alignment, PodSleuth is designed in such a way to make it very easy to optionally support. Supporting it technically places zero dependencies on a library or application. If a distribution happens to provide PodSleuth, then why not take advantage of the properties that would be readily available to you? They’re just strings in HAL! If the properties exist, use them. If not, fall back to what you’re doing today.

Think of your users! There’s a very small majority of users out there who will actually care about what a PodSleuth is, let alone what it’s written in. They just want their iPod to work, and PodSleuth provides a very solid hardware metadata layer in a clean language and platform agnostic way. Of course, these users should already be using or are already using Banshee, which has provided this experience from the get-go.

People who care about the political issue and oppose the platform shouldn’t be using iPods anyway, lest they be hypocrites.