CODEWITHSUNDEEP
linuxlinux-kernelusblinux-device-driveryocto
md.jamal
md.jamal

Reputation: 4517

usb_control_msg returns -EAGAIN

I have a Customized board which interfaces over USB.. I am writing USB Linux driver.

Everything is working fine when I test it on my Virtual Machine.. But when I switch to the real hardware and use Yocto on hardware and run the following code.. It fails with -EAGAIN.. 

retval = usb_control_msg(serial->dev,
        usb_rcvctrlpipe(serial->dev, 0),
        CP210X_GET_MDMSTS,
        USB_DIR_IN | USB_TYPE_VENDOR | USB_RECIP_INTERFACE,
        0,
        i,
        (void *)&modem_status,
        1,
        USB_CTRL_SET_TIMEOUT);

retval returns with -11. I am not sure why this is not happening on the Virtual Machine, as the only difference is that the PIC Board gets connected to X86 Customized board and runs linux..

dmesg output:

transfer buffer not dma capable
------------[ cut here ]------------
WARNING: CPU: 1 PID: 754 at /usr/src/kernel/drivers/usb/core/hcd.c:1595 usb_hcd_map_urb_for_dma+0x3e6/0x5b0
Modules linked in: cp2108(O)
CPU: 1 PID: 754 Comm: test_quad Tainted: G           O    4.14.68-intel-pk-standard #1
task: ffff9a33b7d4a4c0 task.stack: ffff9ce5c0130000
RIP: 0010:usb_hcd_map_urb_for_dma+0x3e6/0x5b0
RSP: 0018:ffff9ce5c0133b08 EFLAGS: 00010296
RAX: 000000000000001f RBX: ffff9a33b7d89780 RCX: 0000000000000000
RDX: ffff9a33bfc9d680 RSI: ffff9a33bfc95598 RDI: ffff9a33bfc95598
RBP: ffff9ce5c0133b28 R08: 0000000000000001 R09: 0000000000000328
R10: ffff9a33ba840068 R11: 0000000000000000 R12: ffff9a33ba2ea000
R13: 00000000fffffff5 R14: 0000000001400000 R15: 0000000000000200
FS:  00007fac9eeed4c0(0000) GS:ffff9a33bfc80000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000003c334e3cb0 CR3: 0000000179498000 CR4: 00000000003406e0
Call Trace:
 usb_hcd_submit_urb+0x420/0xa00
 ? tty_port_open+0xa7/0xd0
 ? tty_ldisc_unlock+0x1a/0x20
 ? tty_open_proc_set_tty+0x7f/0xb0
 ? tty_unlock+0x29/0x40
 ? tty_open+0x38e/0x450
 usb_submit_urb+0x364/0x550
 usb_start_wait_urb+0x5f/0xe0
 usb_control_msg+0xc5/0x110
 cp210x_ioctl+0x4d2/0xe20 [cp2108]
 ? filemap_map_pages+0x129/0x290
 ? do_filp_open+0xa0/0xf0
 serial_ioctl+0x46/0x50
 tty_ioctl+0xe7/0x870
 do_vfs_ioctl+0x99/0x5e0
 ? putname+0x4c/0x60
 SyS_ioctl+0x79/0x90

Can you guys please provide a hint for me to try.. Appreciate your time and efforts.

Upvotes: 3

Views: 913

Answers (1)

md.jamal
md.jamal

Reputation: 4517

I got the solution Kernel >= 4.9 no longer accepts any statically allocated buffer.

Modified the code to use dynamic memory and it worked.

   modem_status = kmalloc(sizeof(unsigned long), GFP_KERNEL);
    if (!modem_status)
        return -ENOMEM;
    for (i = 0; i < MAX_CP210x_INTERFACE_NUM; i++) {
        retval = usb_control_msg(serial->dev,
                usb_rcvctrlpipe(serial->dev, 0),
                CP210X_GET_MDMSTS,
                USB_DIR_IN | USB_TYPE_VENDOR | USB_RECIP_INTERFACE,
                0,
                i,
                (void *)modem_status,
                1,
                USB_CTRL_SET_TIMEOUT);

Upvotes: 5

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