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mandas
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Joined: 13 Nov 2006
Posts: 20

PostPosted: Sun Nov 11, 2012 11:06 am    Post subject: Toshiba laptop Chicony webcam Reply with quote

Hi,

I 've recently purchased a Toshiba Satellite laptop which has a Chicony webcam embedded. This kind of webcam is supported by the Linux kernel, and when it works it works OK. The problem is that I 'm getting a 'USB device disconnected' message and then the webcam disappears, meaning that it's not even listed in lsusb. The webcam is shown up again a few days later for a reason that I haven't managed to identify.

My initial thought to overcome this problem was usb autosuspend (I have it enabled in the kernel). I thought that the problem was that the webcam was suspended and due to buggy hardware/driver there was no way to wake it up like it should be (e.g. when using skype). I 've added a udev rule to set power/control to 'on' in sysfs although it now seems that the webcam doesn't support autosuspend and such a rule was useless.

After that I attached a usb webcam to the same usb hub which supports usb autosuspend and works perfectly. However, with the external attached webcam, the embedded Chicony doesn't disappear. The final thought was to disable autosuspend for the whole usb hub, but I read in the power-management.txt that a hub is considered to be idle, when all of its attached devices are idle. Having the chicony webcam and the internal bluetooth adapted with power/control 'on', I believe that the hub is never going to be suspended. (is that correct?). Same happens when I attach a usb transmitter for wireless kbd/mouse to the same hub. I 've also noticed that skype is waking up the external webcam on any event (a user signs in).

I 've read about other people having the same problem with a workaround of opening/closing the lid but that didn't work for me. I do not use suspend to RAM/disk features and I haven't any ACPI event assigned to the lid.

Any help/suggestion would be highly appreciated, thanks
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ribx
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Joined: 20 Nov 2003
Posts: 212
Location: germany

PostPosted: Tue Nov 13, 2012 2:42 pm    Post subject: Reply with quote

Hi,

all this sounds for me like a powersaving function of the BIOS.

Try to use suspend to ram (pm-suspend) and check, whether the cam wakes up.

And I would also check the BIOS for some kind of powermanagement of USB devices, and disable all of them (and let the kernel do that).

regards
ribx
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mandas
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Joined: 13 Nov 2006
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PostPosted: Tue Nov 13, 2012 9:35 pm    Post subject: Reply with quote

ribx wrote:
all this sounds for me like a powersaving function of the BIOS.

Try to use suspend to ram (pm-suspend) and check, whether the cam wakes up.

And I would also check the BIOS for some kind of powermanagement of USB devices, and disable all of them (and let the kernel do that).


While trying to find BIOS setting for power management of USB devices, the webcam was disappeared again. Finally, it seems that toshiba bios doesn't have any power management setting for USB devices. After that, I compiled a kernel with suspend-to-ram support, went to suspend with pm-suspend, but the webcam didn't show up. If I understand correctly, with suspend-to-ram, even if the BIOS has a USB power management hardcoded, the webcam should wake up after resume. Right ?
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