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Thunderbolt PCIe 4-devices by daisy chain connection problem
Hello everyone I have been developing PCIe device driver through Thunderbolt. However, it was confirmed that up to three devices connected to the daisy chain worked normally, but the fourth device failed to operate the _CopyDeviceMemoryWithIndex() function for connection with the BAR0 App and did not work properly. The standard specification of Thunderbolt 3/4 is said to be supported by daisy chain connection up to 6 units, but in reality, it is only 3 units, so I ask the forum for technical confirmation. Of course total 4 device by 2-port x 2-device daisy chain connecting has working well. And the PCI entry in System information app indicates that all devices have normal load of the PCIe device driver.
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Apr ’25
CoreAudio server plugin: updating kAudioStreamPropertyAvailablePhysicalFormats
Hi, our CoreAudio server plugin supports different clock sources. A switch might result in a change of the selectable sample rates (and other settings). On a clock source switch the plugin reconfigures the set of available kAudioStreamPropertyAvailablePhysicalFormats and announces the change via AudioServerPlugInHostInterface::PropertiesChanged(). However at least the Audio MIDI Setup seems to ignore to update it's UI. The changes are first reflected after selecting another device and re-selecting the device of interest. (Latest macOS, M4 macMini) Is this a bug? Or is our CoreAudio server plugin required to indicate the change in the list of available audio formats differently? Thanks!
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May ’25
Thunderbolt: Implementing shared IO between hosts
Hello all, I am interested in developing a small driver that would facilitate host-to-host communication via Thunderbolt 4/5. While I am aware of features such as Thunderbolt Bridge/Thunderbolt Networking, I find that for my application the overhead is too great. I am interested in sharing a simple, static memory buffer between the two hosts for IO and with some synchronisation primitives. The idea being that the communication is facilitated between different platforms. Would it be possible to develop a driver/service like this? Currently, going through the documentation, to use PCIDriverKit specifying a Vendor and Product Ids is required, so I doubt that this is a viable path. I know that Linux exposes the "XDomain" protocol to announce thunderbolt services (This is the same protocol that is used in macOS to discover Thunderbolt Networking peers). Is this functionality exposed to macOS driver developers?
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May ’25
CarPlay Support
Hi All, We've been working on a new CarPlay-supported App and are hoping for advice on how to achieve this. We have completed the CarPlay Entitledment Request, but have not received any response from Apple. Given we're close to launch on Android, we'd love to have these projects completed together. Any advice on how to make contact with the approvals team, or suggestions on how long this will normally take? If they're no longer taking applications or rejection is high, any guidance would be greatly appreciated too!
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May ’25
Custom VID/PID with com.apple.DriverKit-AppleUSBFTDI
We submitted a request a couple years ago to Apple through the feedback system to add 1 custom vid/pid to the com.apple.DriverKit-AppleUSBFTDI driver. They added it to Monterey and it appears in all macOS versions since Monterey. Not long after submitting this request, we sent a follow-up request to add 2 more pids (same vid, and same personality). Apple eventually added these as well. They appear as an array of pids under the same personality. We are 2 weeks from releasing one of those products (added in the second request) and are just now realizing that the second request was only honored on Sequoia (this fact was masked by us using a temporary ftdi vid/pid during development while waiting for Microsoft to resolve an issue related to adding custom vid/pids to FTDI's Windows driver). All other versions that we are supposed to support (Monterey thru Sonoma) only have the first device. None of the devices from the second request are listed, and consequently this device doesn't match and doesn't expose as a serial port as it should. Our application that works with these devices supports Monterey and up, and we desperately need all devices that we have submitted so far to be available on Monterey and up (thru system updates). I tried starting a code-level support ticket, but they don't have a category for this problem. The feedback mechanism is a black box. You submit the request and get no response. You just wait for weeks/months and then it just appears one day. That was fine then, but we're now in an emergency situation. (FTDI's own dext driver, last time we tried it at least, was unable to be installed after being customized, and they admitted to us during email support that there was some issue on the Apple side that was preventing it from being customized. They haven't updated the dext driver since then, so I assume the situation is still the same) What can we do?
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May ’25
iOS 18 (22G5054d) Developer Beta broke Apple CarPlay
My 2025 Hyundai Tucson SEL was doing fine with Apple CarPlay until last night's update, now it refuses to see/use CarPlay, both by bluetooth and by cable. Mind you, was working perfectly fine yesterday, it still sees my wife's phone via bluetooth and my son's phone via cable. The Tucson's last over-the-air update was 5/23/25, as in, nothing has changed with the Tucson, or my other family phones, which leaves only one variable that changed, my iPhone updating to the latest iOS developer beta.
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Jun ’25
iPad App with custom HID over USB
Hello, I need to develop an application for a customer who is using an iPad. This application needs to read from and send data to a custom HID device connected via USB-C. Using USBDriverKit, the HID device can be detected when plugged into the iPad. However, when trying to open the device with the following code: ivars->interface = OSDynamicCast(IOUSBHostInterface, provider); ret = ivars->interface->Open(this, 0, NULL); It only returns e00002cd. I would like to ask if it is possible to access a custom HID device on iPadOS using USBDriverkit? Any help would be greatly appreciated!!
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183
Jun ’25
IOCTL in MacOS drivers (DriverKit/DEXT)
Hi, In Linux we have this driver structure where the handlers are defined as below: static struct file_operations fops = { .owner = THIS_MODULE, .read = etx_read, .write = etx_write, .open = etx_open, .unlocked_ioctl = etx_ioctl, .release = etx_release, }; So when the user app calls open() with the appropriate file/device handle "etx_open" in the driver is acalled, etc. However, the Apple driver structure that is exposed to developers is different and it has changed drastically with the DriverKit architecture. I have some custom requests from the user app where I need to call this ioctl() type requests on my serial port "tty.myusbserial1234". My driver is derived from IOUserUSBSerial and is working fine for all other practical purposes except for such custom requirements. Has anyone encountered such a problem in MacOS DriverKit and what is the solution or an alternative? https://developer.apple.com/documentation/driverkit/communicating-between-a-driverkit-extension-and-a-client-app This gives a different approach, but the serial ports are accessed via open/read/write/close system calls and tcsetattr and other termios functions to set baud-rate and such. So, the above approcah is not suitable for my purpose. Any ideas/help is very much appreciated. Thanks.
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Jul ’25
CPActionSheetTemplate not detected in presentedTemplate while CPAlertTemplate is
I'm developing a CarPlay app and encountered an inconsistent behavior with template detection. When I present a CPActionSheetTemplate and then print the presentedTemplate property, it returns nil. However, when I present a CPAlertTemplate, the presentedTemplate property correctly returns the template object. This inconsistency is causing issues in my app where I need to check if there's already a presented template before showing another one to avoid conflicts. Why does CPActionSheetTemplate not get detected in presentedTemplate while CPAlertTemplate does? Is this intended behavior or a bug? Any guidance on how to properly detect if a CPActionSheetTemplate is currently presented would be greatly appreciated.
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CarPlay UI Issues in iOS 26: CPListItem accessoryImage Misplaced and Display Problems
Starting with iOS 26, we've noticed that the accessoryImage in CPListItem is not working as expected in CarPlay. Previously, accessoryImage would appear in place of the accessoryType, but now it appears awkwardly next to the detailText, and the image itself is not rendering properly. We have submitted feedback to Apple multiple times, but the issue still persists in the latest beta releases. In general, there seem to be several CarPlay UI problems introduced in iOS 26. For example: In CPPointOfInterestTemplate, the pinImage is displayed at an excessively large size. Scroll positions in lists behave unexpectedly. CPInformationTemplate allows infinite scrolling, which seems unintended. Please take a look into these issues. Thank you.
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Aug ’25
BLE SMP pairing failed due to unspecified reason
Hello, dear Apple engineers. We have recently tried to pair our Android phones and iPhones via BLE SMP, but have encountered a very high probability of pairing failures. Through PacketLogger and Android phone HCI, we have determined that the issue is caused by the iOS side sending an SMP Pairing Failed message during the SMP process. Please help us analyze the reason for this.
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94
Sep ’25
DEXT crashes when app starting
We have developed the driver for the ProCapture video capture card based on PCIDriverKit. The App can communicate with the driver through the UserClient API. Currently, there is an issue where, when the App starts, there is a small probability that it causes a driver crash. However, the crash stack trace does not point to our code but appears to be within the PCIDriverKit framework. We have spent several weeks debugging but still cannot identify the root cause of the crash. Could you please review the crash log and suggest any methods to help pinpoint the issue? com.magewell.ProCaptureDriver-2025-09-15-153522.ips com.magewell.ProCaptureDriver-2025-09-15-082500.ips
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Oct ’25
CarPlay Simulator: How to Change Dock Position for Right-Hand Drive (RHD)
Hello everyone, I'm developing a CarPlay app and am trying to test it with the dock on the right side of the screen, as is standard for right-hand drive vehicles like those in Japan. Currently, the CarPlay Simulator always displays the dock on the left, and I can't find an option to change its position. This is important for ensuring a proper user experience for my target market. Has anyone figured out how to configure the simulator for RHD layouts? Any guidance on how to move the dock to the right would be greatly appreciated. Thanks in advance for your help!
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Sep ’25
IOS alternatives to DriverKit
Hi, We were planning on using DriverKit to develop a USB Driver on IOS for iPhone. Within the DriverKit website, it say 'IOS16.0+' which lead us to believe it was compatible with iPhones running IOS16.0+. However, it appears DriverKit is only available for iPads running iPadOS, and computers running macOS. Are there any alternatives that would allow us to create a device specific USB driver for an iPhone running IOS?
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Sep ’25