About USB Device (gadget) in linux | Hardware solutions for OpenWrt

About USB Device (gadget) in linux.

In most cases, the boards with USB are used as a usb host. Usually we should to tick some fields in make menuconfig to configurate the-usb host.

Configuration of a USB controller for working in USB mode-device (gadget).

Example for a microcontroller marvell 88F6282 (88F6283) of the family kirkwood.

We modify the file arch/arm/mach-kirkwood/common.c as follows:

/*****************************************************************************
 * EHCI0
 ****************************************************************************/
#include 

//static struct resource kirkwood_ehci_resources[] = {
static struct resource kirkwood_usb_resources[] = {
	{
		.start	= USB_PHYS_BASE,
		.end	= USB_PHYS_BASE + 0x0fff,
		.flags	= IORESOURCE_MEM,
	}, {
		.start	= IRQ_KIRKWOOD_USB,
		.end	= IRQ_KIRKWOOD_USB,
		.flags	= IORESOURCE_IRQ,
	},
};

static struct platform_device kirkwood_ehci = {
	.name		= "orion-ehci",
	.id		= 0,
	.dev		= {
		.dma_mask		= &ehci_dmamask,
		.coherent_dma_mask	= 0xffffffff,
		.platform_data		= &kirkwood_ehci_data,
	},
//	.resource	= kirkwood_ehci_resources,
//	.num_resources	= ARRAY_SIZE(kirkwood_ehci_resources),
    .resource	= kirkwood_usb_resources,
    .num_resources	= ARRAY_SIZE(kirkwood_usb_resources),
};

static struct fsl_usb2_platform_data kirkwood_otg_data = {
.operating_mode = FSL_USB2_DR_DEVICE,
.phy_mode       = FSL_USB2_PHY_UTMI,
};

static u64 otg_dmamask = DMA_BIT_MASK(32);

/* OTG gadget device */
struct platform_device kirkwood_otg = {
	.name		= "fsl-usb2-udc",
	.id		= -1,
	.dev		= {
		.dma_mask		= &otg_dmamask,
		.coherent_dma_mask	= DMA_BIT_MASK(32),
		.platform_data		= &kirkwood_otg_data,
	},
	.resource	= kirkwood_usb_resources,
	.num_resources	= ARRAY_SIZE(kirkwood_usb_resources),
};

void __init kirkwood_otg_init(void)
{
	kirkwood_clk_ctrl |= CGC_USB0;
	platform_device_register(&kirkwood_otg);
}

//void __init kirkwood_ehci_init(void)
//{
//	kirkwood_clk_ctrl |= CGC_USB0;
//	platform_device_register(&kirkwood_ehci);
//}
/*****************************************************************************
 * GE00
 ****************************************************************************/

In the file arch/arm/mach-kirkwood/db88f6281-bp-setup.c

static void __init db88f6281_init(void)
{
	/*
	 * Basic setup. Needs to be called early.
	 */

    kirkwood_init();
	….
   kirkwood_otg_init();
      …..
}

In the file drivers/usb/gadget/Kconfig

 config USB_GADGET_FSL_USB2
 	boolean "Freescale Highspeed USB DR Peripheral Controller"
	depends on FSL_SOC || ARCH_MXC || ARCH_KIRKWOOD
 	select USB_GADGET_DUALSPEED
 	help
 	   Some of Freescale PowerPC processors have a High Speed
–

In the kernel:

->Device
    Drivers
        -> USB support (USB_SUPPORT [=y])
            -> USB Gadget Support (USB_GADGET [=y])

CONFIG_USB_MASS_STORAGE for doing the usb-device as an external drive.

After starting the kernel we should connect the module while sending the file system as a parameter to it which will be the external drive. In my case, the file system is presented as a Ram-disk so the load operation a module looks like this:

insmod  /lib/modules/2.6.36/kernel/drivers/usb/gadget/g_mass_storage.ko file=/ dev/ram0 
g_mass_storage gadget: Mass Storage Function, version: 2009/09/11 
g_mass_storage gadget: Number of LUNs=1 
 lun0: LUN: removable file: /dev/ram0 
g_mass_storage gadget: Mass Storage Gadget, version: 2009/09/11 
g_mass_storage gadget: g_mass_storage ready 
fsl-usb2-udc: bind to driver g_mass_storage 
# g_mass_storage gadget: high speed config #1: Linux File-Backed Storage

On the screen we can see the following lot in dmesg:

Apr 23 21:02:21 ubunta kernel: [47718.452228] usb 2-1.3.1: new high-speed USB device number 76 using ehci_hcd 
Apr 23 21:02:21 ubunta kernel: [47718.571196] usb 2-1.3.1: New USB device found, idVendor=0525, idProduct=a4a5 
Apr 23 21:02:21 ubunta kernel: [47718.571201] usb 2-1.3.1: New USB device strings: Mfr=1, Product=2, SerialNumber=0 
Apr 23 21:02:21 ubunta kernel: [47718.571204] usb 2-1.3.1: Product: Mass Storage Gadget 
Apr 23 21:02:21 ubunta kernel: [47718.571207] usb 2-1.3.1: Manufacturer: Linux 2.6.36 with fsl-usb2-udc 
Apr 23 21:02:21 ubunta mtp-probe: checking bus 2, device 76: "/sys/devices/pci0000:00/0000:00:1d.0/usb2/2-1/2-1.3/2-1.3.1" 
Apr 23 21:02:21 ubunta mtp-probe: bus: 2, device: 76 was not an MTP device 
Apr 23 21:02:21 ubunta kernel: [47718.582534] usb-storage 2-1.3.1:1.0: Quirks match for vid 0525 pid a4a5: 10000 
Apr 23 21:02:21 ubunta kernel: [47718.582606] scsi14 : usb-storage 2-1.3.1:1.0 
Apr 23 21:02:22 ubunta kernel: [47719.581749] scsi 14:0:0:0: Direct-Access     Linux    File-CD Gadget   0319 PQ: 0 ANSI: 2 
Apr 23 21:02:22 ubunta kernel: [47719.582773] sd 14:0:0:0: Attached scsi generic sg3 type 0 
Apr 23 21:02:22 ubunta kernel: [47719.587731] sd 14:0:0:0: [sdc] 245760 512-byte logical blocks: (125 MB/120 MiB) 
Apr 23 21:02:22 ubunta kernel: [47719.690417] sd 14:0:0:0: [sdc] Write Protect is off 
Apr 23 21:02:22 ubunta kernel: [47719.690422] sd 14:0:0:0: [sdc] Mode Sense: 0f 00 00 00 
Apr 23 21:02:22 ubunta kernel: [47719.800337] sd 14:0:0:0: [sdc] Write cache: enabled, read cache: enabled, doesn't support DPO or FUA 
Apr 23 21:02:23 ubunta kernel: [47720.025344]  sdc: unknown partition table 
Apr 23 21:02:23 ubunta kernel: [47720.250131] sd 14:0:0:0: [sdc] Attached SCSI removable disk 
Apr 23 21:02:23 ubunta kernel: [47720.569987] EXT2-fs (sdc): warning: mounting unchecked fs, running e2fsck is recommended 
Apr 23 21:02:23 ubunta udisksd[2136]: Mounted /dev/sdc at /media/dima/733ee7cf-c6e8-4ab6-bd6a-24f8192b491c on behalf of uid 1000

If auto mount process is enabled, the standard window of Nautilus will be opened in ubuntu. This window will contain the whole file system of the processor 88F6282

There was an error while first starting, why it happened I dont understood:

# insmod /lib/modules/2.6.36/kernel/drivers/usb/gadget/g_mass_storage.ko 
g_mass_storage gadget: adding config #1 'Linux File-Backed Storage'/bf007068 
g_mass_storage gadget: Mass Storage Function, version: 2009/09/11 
g_mass_storage gadget: Number of LUNs=1 
 lun0: LUN: removable file: (no medium) 
g_mass_storage gadget: I/O thread pid: 557 
g_mass_storage gadget: adding 'Mass Storage Function'/df9a9960 to config 'Linux File-Backed Storage'/bf007068 
g_mass_storage gadget: cfg 1/bf007068 speeds: high full 
g_mass_storage gadget:   interface 0 = Mass Storage Function/df9a9960 
g_mass_storage gadget: Mass Storage Gadget, version: 2009/09/11 
g_mass_storage gadget: g_mass_storage ready 
fsl-usb2-udc: bind to driver g_mass_storage 
g_mass_storage gadget: suspend 
# g_mass_storage gadget: resume 
g_mass_storage gadget: suspend 
g_mass_storage gadget: resume 
g_mass_storage gadget: suspend 
g_mass_storage gadget: resume 
g_mass_storage gadget: suspend 
g_mass_storage gadget: resume 
…..

The solution is re-connecting of usb.