[blog...]

I'm using a Via Epia Mini-ITX board (EN1200) as simple office computer and music box. One of it's main tasks is to provide an internet access via 3G network. The USB-3G modem is a Huawei E620, sold in Germany as "O2 Surfstick".

The Huawei USB modem uses just the common option.c driver which works quite well. But from time to time, there occures some warning in the dmesg and the connection stops working:

------------[ cut here ]------------
WARNING: at drivers/usb/serial/usb-serial.c:324 serial_write_room+0x44/0x51 [usbserial]()
Modules linked in: nls_iso8859_1 nls_cp437 vfat fat iptable_nat nf_nat nf_conntrack_ipv4 nf_conntrack 
ip_tables x_tables sierra pl2303 tvaudio bttv videodev snd_via82xx v4l1_compat ir_common 
snd_ac97_codec compat_ioctl32 i2c_algo_bit ac97_bus v4l2_common videobuf_dma_sg snd_pcm 
ideobuf_core btcx_risc tveeprom snd_timer option snd_page_alloc snd_mpu401_uart snd_rawmidi 
snd_seq_device snd soundcore i2c_viapro usbserial i2c_core 8250_pnp 8250 serial_core button 
via_agp evdev dm_mirror dm_log dm_snapshot usbhid ide_cd_mod cdrom ohci1394 via_velocity 
ieee1394 thermal processor thermal_sys
Pid: 18450, comm: amarokapp Tainted: G W 2.6.27.2 #1
[<c0113736>] warn_on_slowpath+0x40/0x63
[<c011affe>] send_signal+0x1cf/0x1e4
[<c011b1fe>] __group_send_sig_info+0x7/0x9
[<f8ed44d7>] option_write+0x123/0x1aa [option]
[<f8e9a59e>] serial_write+0x6f/0x7a [usbserial]
[<f8e9a522>] serial_write_room+0x44/0x51 [usbserial]
[<c020fad4>] tty_write_room+0x15/0x16
[<c020e141>] opost+0x13/0x1ab
[<c020f62f>] n_tty_receive_buf+0x87b/0xc4b
[<c0287bf9>] sock_aio_write+0xe8/0xf5
[<c0152c8e>] core_sys_select+0x22c/0x27b
[<c010fd14>] place_entity+0x89/0xc2
[<c0110b2c>] check_preempt_wakeup+0xbf/0xf6
[<c020b80e>] flush_to_ldisc+0xd3/0x158
[<f8ed4b08>] option_indat_callback+0x89/0xd9 [option]
[<c0253982>] usb_hcd_giveback_urb+0x60/0x8a
[<c0264416>] uhci_giveback_urb+0xde/0x159
[<c0264a87>] uhci_scan_schedule+0x51c/0x761
[<c0266395>] uhci_irq+0xe3/0xed
[<c025370b>] usb_hcd_irq+0x24/0x58
[<c012cf7b>] handle_IRQ_event+0x1a/0x3f
[<c012dbde>] handle_level_irq+0x50/0x85
[<c01043a3>] do_IRQ+0x48/0x5d
[<c0102cb3>] common_interrupt+0x23/0x30
=======================
---[ end trace 251442a461df9b9e ]---

That's why I'm currently upgrade my linux kernel to current stable release 2.6.28.7. Maybe the driver got more stable? Let's see...

As usual, I do the following steps to compile and install the kernel:

• download the kernel from ftp.eu.kernel.org
• move the /usr/src and unpack
• cp last .config to current linux directory

• make menuconfig the build new .config-file

• make-kpkg -rev ab.1 kernel_image -init 
  

• install: dpkg -i linux-image-2.6.28.7_ab.1_i386.deb

• reboot

done :-)

Postscript two days later:

The kernel is working fine. But the warning in usb-serial still occures from time to time.