First of all, thanks for the response. Actually the document is http://ww1.microchip.com/downloads/en/DeviceDoc/50002277A.pdf (sorry for not pointing it earlier). As I understood, the USB2642 accepts some pass-through commands to deliver SDIO commands to the MMC interface. The driver I need to work is unifi_sdio, which can be downloaded through registering at BlueGiga. Basically it controls the WiFi module using the linux sdio_bus.c interface (sdio_register_driver). It was made to be interfaced directly with a MMC hardware host (most often on embedded microcontroller native SPI/SD interface), but this "thing" I am trying to do seems to not have been done before (use a dual-role USB HCD with a MMC interface to act as a SDIO interface with another peripheral). To avoid having to port the whole driver to a direct SCSI interface and as the document mentions the possibility of delivering SDIO commands using Mass Storage Bulk-Only + Transparent I thought about doing the "glue" in usb-storage land. And regarding ci_hdrc, this is the driver that controls the chip, as it is a dual-role HCD based on chipidea. It seems SMSC (which was bought by Microchip) was the original acquire of ChipIdea technology and developed many USB dual-role chips (for instance LAN9512, LAN9514 and USB2640) which seems to all be controlled by this HCD driver. Probably the storage/mmc interface has nothing to do with the ci_hdrc. 2016-01-18 19:16 GMT-02:00 Matthew Dharm <mdharm-usb@xxxxxxxxxxxxxxxxxx>: > 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 -- Raphael Derosso Pereira Engenheiro de Computação msn: rderossopereira@xxxxxxxxxxx Skype: rderossopereira -- 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
