This mail is in continuation of my last query asked (see details below). How can I fetch the USB device again if I release it ??
I store the IOUSBDeviceInterface and IOUSBInterfaceInterface in a structure and
1. Open the device
2. Open the interface
3. Do Write and Read Pipe operations
4. Close the interface
5. Close the device
Now if I Releaes the interface after Step 5. using Release function, then how can I fetch the device agian next time before communicating with the device ??
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Hi Stuart,
Below are my comments to the asked queries/solutions:
>>I assume that if you quit the first application, then run the second, you >>can access the device from the second application? If not, you have some >>weird bug.
Comments:
Yes, If I quit the first application and run the second, it works perfect. I can then easily access the device from the second application.
>>Perhaps your first application wasn't successful closing the interface and >>device? Did it return any errors when closing?
Comments:
It returns success while closing the interface. I am using "USBInterfaceClose" to close the interface.
>>I'm not sure if you copy/pasted the code below, but it doesn't look right.
Comments: Yes, I mistakely copied pasted wrong in this query. I am using "USBInterfaceOpen" to open the interface.
>>What actual error results do you get from your open & close calls?
Comments: When run with multiple apps, (running app1, then app2 again calling some function from app1) returns:
OpenDevice return success but
Opening the interface returns kIOReturnNoDevice (0x2c0) // no such device
and when i call the app2 it returns
Open Device returns kIOReturnExclusiveAccess (0x2c5) // exclusinve access and device already open.
The error meanins are written in IOReturn.h I took the meanings from there.
>>Have you tried Releasing the IOUSBDeviceInterface once you're done >>communicating with the device? You'd need to fetch it again if you need to >>communicate again, but it doesn't take long.
Comments:
No, I have not released the IOUSBDeviceInterface after communicating with the device. I have only released the same when the device is removed. Else I have not released the device interface. It may be the reason behind such issue.
Please tell :
1. When do I need to release the device Interface ? Each time I communicate with the key i.e after closing the device and interface, Do I NEED TO release the device interface ???
2. Do I need to release the IOUSBInterfaceInterface also ??
>>Why are you doing this at all, if your device is "USB BULK device" - do you >>mean Mass Storage Bulk Only? If so, you don't need a driver, Mac OS X has >>one.
Comments:
Its our own , vendor specific bulk device, and not a mass storage bulk.
All suggestions/comment are welcome.
Thanks and Regards,
rohitdhamija
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