Hello....
I am in need of some advise and guidance. I am working slowly on device support for a couple of USB chips that have multiple, but somewhat mutually exclusive, behaviors. The first is enhancements to ufdti to support the MPSSE engine that some of the FTDI chip variants have. This engine allows the chip to be a I2C bus, SPI bus and provides some simple GPIO, and a bunch of other stuff, as well as the normal USB UART. It is not possible to use all of the modes at the same time. That is, these are not separate devices, but modes within one device. Or another way, depending on the mode of the chip you get different child devices attached to it. I am curious on what the thoughts are on how this might be modeled. I see a few options for doing this, such as simply matching all of the possible children and using sysctl to enable the one you want. Probably followed by a rescan call. That seems ugly, however. The use of 'drvctl -r -a <attribute>' seemed to hold promise. It seems like a better idea to require the detachment of whatever followed by the rescan with the attribute indicating which sort of thing you wanted to attach (detach ucom in favor of i2c, for example). But I do not completely understand if this sort of thing is possible. The second chip is the MCP2221 which provides some of the same features as the FTDI MPSSE engine. It has a built in UART which is a separate USB device and then a USB device that can be programmed to provide I2C, GPIO, some DAC a bit of ADC (low number of bits in both of those cases, but still interesting enough). You can probably always just provide the I2C bus and then flip the behaviors of the GPIO pins by setting their alt settings. This chip may be a bit simpler to deal with with the using gpio alt settings and such, but I also have not looked at this one as much. If I can get these to work, the end result will be that any system with USB, including virtual systems with USB devices presented to it in some way, can have I2C, simple GPIO and maybe SPI ... and this is the place I want to end up for my own needs. I have looked around the tree for other devices that do this sort of thing and didn't really find any that tried to deal with this sort of situation, but I will admit I looked mostly at the MI devices. Any thoughts would be appreciated, -- Brad Spencer - b...@anduin.eldar.org - KC8VKS - http://anduin.eldar.org
