I'm actually working on a direct DSLR app using USB host, a preview of which should hopefully be released by the end of the week (alpha, not beta).
I'm mentioning this because it works on the Galaxy S2 with 2.3.4. I've not been able to get it to work on the Galaxy S1 with 2.3.4, but it just goes to show, it may not be 100% necessary to be running HC 3.1 to support it (as evidenced by the SGS2).
What kind of connection cable does the HTC Flyer have ? Micro USB ? If so, I'd advise to give the test app a spin when I release it if you happen to have a USB host cable.
Either way, the chips themselves have supported it for years and years, that's not the issue. Kernel and framework support and such is the problem.
i5800, i9000*2, P1000*2, P7100, i9100*2, N7000, P6800, i9300, N7100, i9505
T LT30p, Z C6603
Galaxy*2, N7, N10
SuperSU, Mobile ODIN, TriangleAway, DSLR Controller, CF-Root, USB Host Diagnostics, ExynosAbuseAPK, Live dmesg+logcat, NoMoarPowah!, CF-Bench, Chainfire3D, CF.lumen, SGS2 SIM Unlocker, GingerBreakAPK, SuperPower, and more!
Windows Mobile 5/6
Wizard*2, Kaiser, Touch, Diamond, Pro, HD*2, Diamond 2, Pro 2*2, HD2*2
i780, i900*2, i8000*2, b7300, b7320, b7330, b7620*2, b6520
WMWifiRouter, KaiserTweak, FPUEnabler, WMLongLife, WMRegOptimizer, CFC+GUI, TF3D+v2 ports, Kaiser+Omnia2+Snapdragon 3D drivers, GfxBoost, and more!
Windows Phone 7
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