If you were going to do this as some sort of "glue", I would suggest creating a new sdio_bus which is actually a SCSI client (the same way sr, sd, and sg are "clients" of SCSI core -- I know that's not the right terminology) and can translate the SDIO requests into the relevant SCSI vendor-specific commands. Matt On Mon, Jan 18, 2016 at 5:34 PM, Raphael <raphaelpereira@xxxxxxxxx> wrote: > 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 -- 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
