I'm using ZTE Evolution EV-DO USB modem. On connect, usbserial detects modem as /dev/ttyUSB0 (and 1, and 2, where is ttyUSB0 is real modem tty). I'm configured ppp connection (tryed gnome-ppp, kppp, wvdial and pppd directly). In all cases pppd hungs, and syslog contains next information:
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[13536.262455] WARNING: at /build/buildd/linux-2.6.27/drivers/usb/serial/usb-serial.c:324 serial_write_room+0x75/0x80 [usbserial]()
[13536.262455] Modules linked in: ppp_async ppp_generic slhc option usbserial isofs udf crc_itu_t ipv6 af_packet i915 drm binfmt_misc rfcomm bridge stp bnep sco l2cap bluetooth ppdev cpufreq_powersave cpufreq_stats cpufreq_conservative cpufreq_ondemand freq_table cpufreq_userspace pci_slot sbs sbshc iptable_filter ip_tables x_tables sbp2 parport_pc lp parport joydev pcmcia acer_wmi led_class psmouse serio_raw pcspkr evdev uvcvideo compat_ioctl32 videodev nsc_ircc v4l1_compat battery irda ac crc_ccitt ieee80211_crypt_tkip wl(P) ieee80211_crypt snd_hda_intel container snd_pcm_oss snd_mixer_oss video output sdhci_pci sdhci tifm_7xx1 snd_pcm mmc_core tifm_core yenta_socket rsrc_nonstatic pcmcia_core snd_seq_dummy snd_seq_oss snd_seq_midi snd_rawmidi wmi snd_seq_midi_event snd_seq button snd_timer snd_seq_device iTCO_wdt iTCO_vendor_support intel_agp agpgart shpchp pci_hotplug snd soundcore snd_page_alloc ext3 jbd mbcache sr_mod cdrom sd_mod crc_t10dif sg ata_piix ata_generic usbhid hid ahci pata_acpi libata scsi_mod ohci1394 dock ieee1394 tg3 libphy uhci_hcd ehci_hcd usbcore thermal processor fan fbcon tileblit font bitblit softcursor fuse
[13536.262455] Pid: 0, comm: swapper Tainted: P W 2.6.27-7-generic #1
[13536.262455] [<c037c406>] ? printk+0x1d/0x1f
[13536.262455] [<c0131de9>] warn_on_slowpath+0x59/0x90
[13536.262455] [<f8891793>] ? uhci_urb_enqueue+0x53/0x2d0 [uhci_hcd]
[13536.262455] [<f88d7fa9>] ? usb_hcd_submit_urb+0x79/0x180 [usbcore]
[13536.262455] [<f88d838f>] ? usb_submit_urb+0xff/0x260 [usbcore]
[13536.262455] [<f8e7655e>] ? option_write+0xe/0x230 [option]
[13536.262455] [<c0151c84>] ? clockevents_program_event+0x14/0x150
[13536.262455] [<c037dfae>] ? account_scheduler_latency+0xe/0x220
[13536.262455] [<f8e7647c>] ? option_write_room+0xc/0x70 [option]
[13536.262455] [<f8e7647c>] ? option_write_room+0xc/0x70 [option]
[13536.262455] [<f9134665>] serial_write_room+0x75/0x80 [usbserial]
[13536.262455] [<c02a676d>] tty_write_room+0x1d/0x20
[13536.262455] [<c02a421f>] opost+0x1f/0x260
[13536.262455] [<c01be546>] ? kill_fasync+0x16/0x50
[13536.262455] [<c02a60ca>] n_tty_receive_char+0x54a/0x700
[13536.262455] [<c02a64d8>] n_tty_receive_buf+0x258/0x4b0
[13536.262455] [<c0123454>] ? __enqueue_entity+0xd4/0x100
[13536.262455] [<c0124aba>] ? enqueue_entity+0xda/0x2f0
[13536.262455] [<c012a708>] ? enqueue_task_fair+0x48/0x50
[13536.262455] [<c0120f97>] ? enqueue_task+0x57/0x70
[13536.262455] [<c02a7f8b>] ? tty_ldisc_try+0x3b/0x50
[13536.262455] [<c02a2496>] flush_to_ldisc+0xf6/0x1c0
[13536.262455] [<c02a25cb>] tty_flip_buffer_push+0x6b/0x80
[13536.262455] [<f8e76f43>] option_indat_callback+0xb3/0x12c [option]
[13536.262455] [<f88d6d04>] ? unmap_urb_for_dma+0x14/0x130 [usbcore]
[13536.262455] [<f88d8684>] ? usb_unanchor_urb+0x14/0xb0 [usbcore]
[13536.262455] [<f88d6e6d>] usb_hcd_giveback_urb+0x4d/0xd0 [usbcore]
[13536.262455] [<c037e62d>] ? _spin_lock+0xd/0x10
[13536.262455] [<f888fd1c>] uhci_giveback_urb+0x8c/0x200 [uhci_hcd]
[13536.262455] [<f888fa2a>] ? uhci_result_common+0x22a/0x300 [uhci_hcd]
[13536.262455] [<f889017f>] uhci_scan_qh+0x23f/0x460 [uhci_hcd]
[13536.262455] [<c01136c0>] ? lapic_next_event+0x20/0x30
[13536.262455] [<f8890553>] uhci_scan_schedule+0x153/0x270 [uhci_hcd]
[13536.262455] [<c0136976>] ? set_normalized_timespec+0x16/0x90
[13536.262455] [<f8891b6b>] uhci_irq+0x7b/0x160 [uhci_hcd]
[13536.262455] [<f88b466a>] ? ehci_irq+0x4a/0x180 [ehci_hcd]
[13536.262455] [<c014e63b>] ? getnstimeofday+0x4b/0x100
[13536.262455] [<f88d69e0>] usb_hcd_irq+0x40/0x90 [usbcore]
[13536.262455] [<c01770b1>] handle_IRQ_event+0x41/0x80
[13536.262455] [<c0178954>] handle_fasteoi_irq+0x74/0xe0
[13536.262455] [<c0106c15>] do_IRQ+0x45/0x80
[13536.262455] [<c0105003>] common_interrupt+0x23/0x30
[13536.262455] [<c01700d8>] ? __audit_mq_getsetattr+0x68/0xb0
[13536.262455] [<f8876800>] ? acpi_idle_enter_bm+0x268/0x2b7 [processor]
[13536.262455] [<c02dbf7b>] cpuidle_idle_call+0x7b/0xd0
[13536.262455] [<c010288d>] cpu_idle+0x7d/0x140
[13536.262455] [<c036edd3>] rest_init+0x53/0x60
[13536.262455] =======================
[13536.262455] ---[ end trace 9f1d4cd5e0f887db ]---
This modem is tested on two notebooks (I can give you hardware details if needed) with the same result.
Under Windows system modem works properly.
As I understand this is kernel module usbserial bug. I will be glad to give you any help to resolve this trouble.
[This is an automated message. Apologies if it has reached you inappropriately.]
This bug was reported against the linux-meta package when it likely should have been reported against the linux package instead. We are automatically transitioning this to the linux kernel package so that the appropriate teams are notified and made aware of this issue. Thanks.