bInterfaceNumber for multiple interface usb-cdcacm device

you are right, you can't define multiple interface numbers within one IOKitPersonality. But you can define multiple IOKitPersonalities.

IOKitPersonalities is a dictionary of dictionaries. The keys are strings (which can be anything meaningful to you, the OS doesn't care what they are), each value is a dictionary. Copy your dictionary which matches against bInterfaceNumber=1, and modify it to match against bInterfaceNumber=2.

I believe the rules outlined still apply.

https://developer.apple.com/library/archive/qa/qa1076/_index.html

I have a USB composite device with multiple interfaces that support CDC-ACM UARTs.

My custom driver (.dext) loads and works for a single-channel USB-CDC-CCM device with these entries in the Info.plist:

Two different answers here:

(1) The "IOKitPersonalities" dictionary is basically a "list"* of specific match criteria, each of which is treated independently by the kernel. So the (general) way you match the same driver against different hardware configurations is by defining a separate personality dictionary for each configuration. See this Info.plist for a concrete example of this:

/System/Library/DriverExtensions/com.apple.AppleUserHIDDrivers.dext/Info.plist

Note that "IOKitPersonalities" is defined as a dictionary (instead of an array) because the top-level key value ends up being used in the IORegistry (it's returned by IORegistryEntryGetName), and using a dictionary ensures that the entry names are unambiguous within a given driver bundle. The keys themselves are not meaningful, nor does entry order matter.

(2) The USB Family has very specific driver matching rules, as described in QA1076. That includes "wild card" matching within the valid configuration set. The wild card match configuration for this would be:

<key>bInterfaceNumber</key>
<string>*</string>

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Kevin Elliott
DTS Engineer, CoreOS/Hardware

Hi Kevin,

Is there a way to call custom ioctl calls from user client/application to the dext? My application needs to set certain custom settings to the usb uart device and it seems there are no base class functions that I can override in IOUserSerial class.

Any help in this regard is very much appreciated.

Thanks.

Is there a way to call custom ioctl calls from user client/application to the dext?

I'm not sure what you mean here. The user client architecture lets you create your own communication channel between your DEXT and user space, at which point you can do whatever you want. I don't see any reason why a SerialDriverKit DEXT couldn't also implement a user client*.

*The one qualifier here is the broad "what are you actually trying to do"?

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Kevin Elliott
DTS Engineer, CoreOS/Hardware

Hi Kevin,

As you know serial ports can be opened, configured and read/write operations can be performed using open(), tcsetattr(), read() and write() system calls, as in the below sample code. Here tcsetattr() in turn calls ioctl() system call, I think. But all these tcsetattr()/ioctl()/read()/write() corresponding calls to the driver are implemented in the base class and are not exposed as virtual functions in derived IOUserUSBSerial() class.

So if I need to call/send any specific custom request to the driver with a special IOCTL code, what are the options available to the user is my question.

This is the sample user app code which uses system calls to access the serial ports.

BEGIN-->

const char *portname = "/dev/cu.usbserial-YOURDEVICEID"; 

int serial_port = open(portname, O_RDWR | O_NOCTTY | O_SYNC);

// Check for errors opening the serial port
if (serial_port < 0) {
    printf("Error %i from open: %s\n", errno, strerror(errno));
    return 1;
}

// Configure the serial port settings
struct termios tty;
if (tcgetattr(serial_port, &tty) != 0) {
    printf("Error %i from tcgetattr: %s\n", errno, strerror(errno));
    return 1;
}

cfsetospeed(&tty, B9600); // Set output baud rate (e.g., 9600)
cfsetispeed(&tty, B9600); // Set input baud rate

tty.c_cflag |= (CLOCAL | CREAD); // Enable receiver, ignore modem control lines
tty.c_cflag &= ~PARENB;          // No parity
tty.c_cflag &= ~CSTOPB;          // One stop bit
tty.c_cflag &= ~CSIZE;           // Clear all size bits
tty.c_cflag |= CS8;              // 8 data bits

tty.c_lflag &= ~(ICANON | ECHO | ECHOE | ISIG); // Raw input
tty.c_oflag &= ~OPOST;                          // Raw output

// Apply the settings
if (tcsetattr(serial_port, TCSANOW, &tty) != 0) {
    printf("Error %i from tcsetattr: %s\n", errno, strerror(errno));
    return 1;
}

// Write data to the serial port
char msg[] = "Hello, serial port!\n";
write(serial_port, msg, strlen(msg));

// Read data from the serial port (example)
char read_buf[256];
int num_bytes = read(serial_port, read_buf, sizeof(read_buf) - 1);
if (num_bytes < 0) {
    printf("Error %i from read: %s\n", errno, strerror(errno));
} else if (num_bytes > 0) {
    read_buf[num_bytes] = '\0'; // Null-terminate the string
    printf("Received: %s\n", read_buf);
}

close(serial_port); // Close the serial port

<--END

So, my requirement is if I need to call ioctl(serial_port, MY_IOCTL_REQUEST, &myargs,...) what is the corresponding code/method that needs to be overridden in my driver (.dext) whose IOClass is IOUserSerial and the driver's base class is IOUserUSBSerial.

Thanks in advance.