Hi Mandeep, Too many question, separate and ask them. 1. USB Gadget is the basic driver which is nothing but USB Device(or Slave driver). This will make the Board as USB Device. But u need more other then just this driver. 2. Based on Gadget: you can use File Storage Module if you need to make your board as USB Memory stick. Just change few configuration in file_storage.c like wise there are many modules( or application drivers) which use Gadget driver. Now, Next question: you can compile them separately means outside the Linux kernel as module and load them. Also enable & use USB Mon to see USB Protocol flow. Grep usb_gadget_register_driver / usb_gadget_unregister_driver API's to see if any body is using them in your kernel. Regards Vivek -----Original Message----- From: kernelnewbies-bounce@xxxxxxxxxxxx [mailto:kernelnewbies-bounce@xxxxxxxxxxxx] On Behalf Of Mandeep Sandhu Sent: Monday, January 12, 2009 10:57 AM To: Kernel Newbies Subject: newbie usb gadget query Hi All, I had a few doubts regarding USB gadgets under linux. I posted the bellow query to the linux-usb mailing list, but since I haven't received any replies, I thought I'd try my luck here! :) Please let me know if this is not the right place for this query... I'm new to USB device driver development. I've mostly done a few LKMs (and an ethernet driver) on 2.6 kernels. And this too was sometime back (around 1.5 yrs!)...so my knowledge on a few things might be rusty! :) I'm working on an embedded board and would like to validate a few assumptions here before proceeding to start work on them. The board is a Compulab CM-X270L (PXA270). This board has USB master as well as a slave port. It's currently running a patched 2.6.16 kernel (the patch is from Compulab). It runs Compulab's Debian distribution - "Debian GNU/Linux 3.1". We need to use the board as a USB slave to a machine which has a USB master (root hub). This machine runs a proprietary OS and we do not have access to it's source code and/or any other means to access it's internals. This proprietary OS supports the following USB classes: * CDC-ACM: Full ACM specs * CDC-ECM: The USB host side diver on the OS, only works with one particular USB-ethernet dongle (say chip-X). So I'm guessing the OS does not support the full ECM specs. We need to use the board as a slave and test it's interoperability with the host for the above mentioned USB classes. I plan to do the following: 1) CDC-ACM: Compile the USB gadget serial driver as a LKM for the board. If the module loads successfully, connecting the slave port to the host should make it (the slave), enumerate successfully as an ACM device. 2) CDC-ECM: This one's a bit tricky! I understand that the ethernet is implemented in drivers/usb/gadget/ether.c. But, since the host side driver is written to work with a particular chipset, will it work "AS IS" with the ethernet gadget driver? Also, in case it doesn't work, can I tweak the gadget driver to make it work/enumerate correctly with the host? Basically I'll be "faking" the chip in s/w...is this possible to do? Also, how can I verify that the kernel has recognized the USB slave device? During kernel configuration, we can choose gadget support as a module. The following link states that the USB device functionality is not supported in 2.6.16 kernels: http://www.compulab.co.il/mediawiki/index.php5?title=Linux_Kernel_for_CM -X270#USB_device Using the link given on the above page...I downloaded the complete gadget source: http://handhelds.org/cgi-bin/cvsweb.cgi/linux/kernel26/drivers/usb/gadge t/?only_with_tag=K2-6-16-DEV After this, when compiling the kernel, when I enabled the USB gadget support, I could see the device controller for PXA27x boards. This produced the pxa27x_udc LKM. On inserting the module I got the following error: pxa27x_udc: exports duplicate symbol usb_gadget_register_driver (owned by kernel) If i grep /proc/kallsyms I can see this symbol exported. Is this symbol exported by a module or is this due to gadget support being built into the currently running kernel? There's no way I can find out what configuration the currently runnig kernel (2.6.16-cmx270) was built, since the required file is not under /boot!! Another pain-point is the fact that I can't re-flash the kernel on the Compulab board with a newer version (I think 2.6.24 has support for USB device). This is because the board directly boots up the kernel and does not stop at the prompt. I've followed the procedure mentioned here: http://www.compulab.co.il/mediawiki/index.php5?title=Getting_started_wit h_Linux_on_CM-X270#Image_installation but this doesn't seem to work, the bootloader (ARMMon) still boots the kernel directly! :( Any clues as to how to circumvent this problem? Any suggestions are welcome. Thanks for your time. Regards, -mandeep -- To unsubscribe from this list: send an email with "unsubscribe kernelnewbies" to ecartis@xxxxxxxxxxxx Please read the FAQ at http://kernelnewbies.org/FAQ -- To unsubscribe from this list: send an email with "unsubscribe kernelnewbies" to ecartis@xxxxxxxxxxxx Please read the FAQ at http://kernelnewbies.org/FAQ
