site_archiver@lists.apple.com Delivered-To: darwin-dev@lists.apple.com Thread-index: AcjXqjKdl+atJKepQJeMOf9A6CwrHQAynxSw Thread-topic: USB Mass Storage: command size limits Hi Chris, let me just check I've got the right end of the stick....

You should check the IOUSBMassStorageClass code which allows you to specify keys in the SCSI Device Charateristics dictionary including max block count or max byte count (i.e. you don't have to write any code to do this).

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I was wondering if I could tweak this for our USB

device, which can

...

support bigger commands. However it looks like the

traffic is limited by

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IOBlockStorageDriver.

Yes, you can and should.

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How could I change the behaviour of

IOBlockStorageDriver? I can subclass

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and instantiate IOBlockStorageServices from a custom LUN

driver, but how

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could I cause a subclass of IOBlockStorageDriver to be

loaded for my

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device?

Refer to the IOUSBMassStorageClass and you can look at information in AppleStorageDrivers plugins that shows how some device overrides enable different I/O sizes...

I've got a working plist that installs a subclass of IOUSBMassStorageDevice (I know you said I don't have to write code but it's easier to tell if it matched my plist if I subclass... I'll change that later). In the plist I've included the SCSI Device Characteristics dictionary, containing IOMaximumByteCountRead, IOMaximumBlockCountRead, IOMaximumByteCountWrite, IOMaximumBlockCountWrite They now appear in IOReg explorer, and are transported up to the PeripheralDeviceNub and the LUN driver. However they don't appear in the IOBlockStorageServices object or any further up the food chain. The IOBlockStorageServices object also has IOMaximumSegmentCountRead/Write properties set to 32, which I guess is 128kB. Am I on the right track? Cheers, Andy _______________________________________________ Do not post admin requests to the list. They will be ignored. Darwin-dev mailing list (Darwin-dev@lists.apple.com) Help/Unsubscribe/Update your Subscription: http://lists.apple.com/mailman/options/darwin-dev/site_archiver%40lists.appl... This email sent to site_archiver@lists.apple.com