If usb-storage detects the device as a storage device, then it isn't exposing the "raw" MMC device. Generally speaking, the usb-storage driver doesn't know anything specific about MMC; for spec-compliant devices, it frames the commands in terms of "give me xxxx bytes starting at linear address yyyy". For devices with vendor-specific protocols it's a little more complicated, but not that far off. It would be interesting to see the USB descriptors from the USB2642 device. I wonder if it has multiple interfaces. Tho, if this document is to be believed -- http://ww1.microchip.com/downloads/en/DeviceDoc/50002283A.pdf -- it does not. In fact, it implements the I2C interface via vendor-specific SCSI pass-through commands, which usb-storage will frame and send over the wire quite happily. Are you sure ci_hdrc applies here? Doing some quick googling, that looks like an HCD rather than something for the USB2642.... Matt On Mon, Jan 18, 2016 at 11:39 AM, Raphael <raphaelpereira@xxxxxxxxx> wrote: > Hi, > > I developed a hardware that has a Microchip USB2642 (USB Hub with MMC > interface), which is kernel supported by chipidea IP (ci_hdrc) driver. > > I connected a Bluegiga WF111-A WiFi module to the MMC interface of the > USB2642. So, in a hardware sense, everything is fine. > > The problem is that the only driver available from BlueGiga uses linux MMC > stack. So although usb-storage detects the module as a SCSI disk interface > (/dev/sda), the driver doesn't work, as it searches the MMC stack for the > module, and finds nothing. > > I have been taking a look at usb-storage driver, SDIO specs and a specific > document from Microchip that shows a "SDIO over USB bridge" reference, which > actually is what usb-storage does (SCSI Bulk-Only with SCSI Transparent > transport) and so I wonder if is it reasonable to write a "MMC host > interface/bridge" in the usb-storage driver so that any SDIO driver can > attach to the USB subsystem. > > At first it seems only that I need to make some kind of glue between both > stacks (usb-storage and mmc). > > Or, maybe the right option is to ignore usb-storage and implement usb > bindings on a custom MMC host. So I want some opinions before I begin to > make crap. > > My question is: Is this the correct approach or am I being stupid? > > Thanks! > -- > Raphael Derosso Pereira > -- Matthew Dharm Maintainer, USB Mass Storage driver for Linux -- To unsubscribe from this list: send the line "unsubscribe linux-usb" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
