Understand the role of drivers in bridging the gap between software and hardware, ensuring smooth hardware functionality.

Drivers Documentation

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is XPC from app to CMIOExtension possible?
I built an app which hosts a CMIOExtension. The app works, and it can activate the extension. The extension loads in e.g. Photo Booth and shows the expected video (a white horizontal line which moves down the picture). I have a couple of questions about this though. The sample Camera Extension is built with a CMIOExtension dictionary with just one entry, CMIOExtensionMachServiceName which is $(TeamIdentifierPrefix)$(PRODUCT_BUNDLE_IDENTIFIER) This Mach service name won't work though. When attempting to activate the extension, sysextd says that the extensions has an invalid mach service name or is not signed, the value must be prefixed with one of the App Groups in the entitlement. So in order to get the sample extension to activate from my app, I have to change its CMIOExtensionMachServiceName to <my team ID>.com.mycompany.my-app-group.<myextensionname> Is this to be expected? The template CMIOExtension generates its own video using a timer. My app is intended to capture video from a source, filter that video, then feed it to the CMIOExtension, somehow. The template creates an app group called "$(TeamIdentifierPrefix)com.example.app-group", which suggests that it might be possible to use XPC to send frames from the app to the extension. However, I've been unable to do so. I've used NSXPCConnection * connection = [[NSXPCConnection alloc] initWithMachServiceName:, using the CMIOExtensionMachServiceName with no options and with the NSXPCConnectionPrivileged option. I've tried NSXPCConnection * connection = [[NSXPCConnection alloc] initWithServiceName: using the extension's bundle identifier. In all cases when I send the first message I get an error in the remote object proxy's handler: Error Domain=NSCocoaErrorDomain Code=4099 "The connection to service named <whatever name I try> was invalidated: failed at lookup with error 3 - No such process." According to the "Daemons and Services Programming Guide" an XPC service should have a CFBundlePackageType of XPC!, but a CMIOExtension is of type SYSX. It can't be both. Does the CMIOExtension loading apparatus cook up a synthetic name for the XPC service, and if so, what is it? If none, how is one expected to get pixel buffers into the camera extension?
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7.9k
May ’22
Launching Network System Extension from LaunchAgent
In another question on this forum (https://developer.apple.com/forums/thread/124775) eskimo stated that launching a system extension from an daemon is not the right approach and that the OSSystemExtensionRequest.activationRequest API should be called from an App. My question is, does this same restriction apply to a LaunchAgent started App? If so, to ensure activation as soon as possible is the only option to use a SMLoginItemSetEnabled helper to start the App on login?
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1.4k
Mar ’22
Adjust Latency Timer for the AppleUSBFTDI Driver
How do I adjust the latency timer for the AppleUSBFTDI driver? I am developing an app in Swift using Xcode on a MacBook Pro M1 running Big Sur, for clinical brain-computer interface (BCI) research. The app needs very low-latency streaming from an external USB device. The external device is a headset which connects via Bluetooth to an FT231X chip mounted on a USB-Serial dongle. The FT231X chip reads timestamped EEG data from the headset. The issue is that the AppleUSBFTDI driver is buffering the packets coming in from the headset, which causes jitter in the timestamps. Typically, with proprietary drivers from FTDI, the solution is to reconfigure them to reduce the latency timer to 1ms. The Info.plist is edited to add new key/value pairs. Is there a similar solution for Apple's built-in driver?
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Sep ’21