IOUSBHost

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Create host-mode user space drivers for USB devices using IOUSBHost.

Posts under IOUSBHost tag

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Accessing Events from Video Device
I have an intra-**** video device that's supported by Apple's AVCaptureDevice. I can use the AV classes to connect to the device and get video. However, this device has a button that's used to acquire still images from the video stream. I can't use the IOUSBDeviceInterface to do an asynchronous read, because the Apple driver has the device opened exclusively. How do I go about receiving the button event in this scenario? I know which pipe to read, based on a bus analyzer when I run this on Windows, I just need to know how to access that pipe when the device is opened by another process.
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Oct ’24
USB driver for MIDI keyboard
Greetings. I'm trying to build an Apple Silicon driver for a Roland keyboard which is no longer supported by the manufacturer. The most recent official driver is from 2010. From my limited understanding of the Apple documentation, it seems to be telling me that I need to build a codeless dext which overrides some sort of base class. The keyboard uses bog standard USB 1.0 to communicate with the host. Total newb in the driver area so if anyone could point me in the right direction on where to start I would be totally grateful.
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502
Mar ’24
Working around the lack of USB FTDI
I'm working on hardware that communicates wireless and wired with mobile systems. Anything non-i[Pad]OS we can connect via USB and achieve great bandwidth, in situations where this is necessary. Since i[pad]OS does not support FTDI class compliant devices through USB (and also omits the IOUSB framework), I wonder whether we have a way to "work around" this, e.g. how about (ab)using another protocol that i[pad]OS allows? Concretely, would you think it's possible to tunnel our serial data stream via USBHID?
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561
Mar ’24
Determining the USB hub port to which an iPad is connected
Hi. I wish I'd found a way to determine the USB hub port to which an iPad is connected, even if it means creating a one-time mapping of identifiers and ports beforehand. I thought I'd find some hardware identifiers that might help, but they appear to fluctuate depending on how the iPad carts are connected to the Mac. Is there anything reliable to achieve the desired result? Thanks for your insights. Franck
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528
Jan ’24
USB DriverKit returning large asynchronous data
this is a repost with more appropriate tags. The original is here: https://developer.apple.com/forums/thread/744268 Can anyone advise, or give example of, communicating large (>128 byte) incoming buffers from a dext to a user-space app? My specific situation is interrupt reads from a USB device. These return reports which are too large to fit into the asyncData field of an AsyncCompletion call. Apple's CommunicatingBetweenADriverKitExtensionAndAClientApp sample shows examples of returning a "large" struct, but the example is synchronous. The asynchronous example returns data by copying into a IOUserClientAsyncArgumentsArray, which isn't very big. I can allocate a single buffer larger than 4K in user space, and communicate that buffer to my driver as an IOMemoryDescriptor when I set up my async callback. The driver retains the descriptor, maps it into its memory space and can thus write into it when the hardware returns interrupt data. The driver then calls AsyncCompletion, which will cause my user-side callback to be called, so the user side software knows that there's new data available in the previously allocated buffer. That's fine, it works, but there are data race problems - since USB interrupt reads complete whenever the hardware has provided data, incoming completions happen at unpredictable times, so the shared buffer contents could change while the user side code is examining them. Is there an example somewhere of how to deal with this? Can I allocate memory on the driver side on demand, create an IOMemoryDescriptor for it and return that descriptor packed inside the asyncData? If so, how does the driver know when it can relinquish that memory? I have a feeling there's something here I just don't understand...
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676
Jan ’24
USB DriverKit returning large asynchronous data
Can anyone advise, or give example of, communicating large (>128 byte) incoming buffers from a dext to a user-space app? My specific situation is interrupt reads from a USB device. These return reports which are too large to fit into the asyncData field of an AsyncCompletion call. Apple's CommunicatingBetweenADriverKitExtensionAndAClientApp sample shows examples of returning a "large" struct, but the example is synchronous. The asynchronous example returns data by copying into a IOUserClientAsyncArgumentsArray, which isn't very big. I can allocate a single buffer larger than 4K in user space, and communicate that buffer to my driver as an IOMemoryDescriptor when I set up my async callback. The driver retains the descriptor, maps it into its memory space and can thus write into it when the hardware returns interrupt data. The driver then calls AsyncCompletion, which will cause my user-side callback to be called, so the user side software knows that there's new data available in the previously allocated buffer. That's fine, it works, but there are data race problems - since USB interrupt reads complete whenever the hardware has provided data, incoming completions happen at unpredictable times, so the shared buffer contents could change while the user side code is examining them. Is there an example somewhere of how to deal with this? Can I allocate memory on the driver side on demand, create an IOMemoryDescriptor for it and return that descriptor packed inside the asyncData? If so, how does the driver know when it can relinquish that memory? I have a feeling there's something here I just don't understand...
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659
Jan ’24
How to develop a driver extension for a USB mass storage device
I am currently in the process of developing a DEXT for a USB based external mass storage device using the USBDriverKit framework. IOUSBHostInterface is used as the provider to communicate with the interface's endpoints and I am successful in it. As per the IOUSBHostInterface documentation, To use a host interface object, call Open to create a new session between the interface and your driver. After successfully opening your session, you can request information from the interface and set up pipes to communicate with the interface's endpoints. Remember to close the session you opened in the Stop method of your driver. However, calling Open gains exclusive access to the USB interface and does not allow other services to access the interface. Also, to let go of the exclusive access, Close method can be called but in the Stop method which is called only once during the lifecycle of the extension (when the DEXT is unloaded). As a result of this, Apple's mass storage related KEXTs (media and partition related specifically) do not match the interface and so the filesystem of the drive in question does not get mounted whenever the DEXT has matched the interface. Is this exclusive access a limitation of USBDriverkit or is there any way to get around this issue in this case?
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842
Nov ’23