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    SubjectRe: Network drivers that don't suspend on interface down
    Matthew Garrett wrote:
    >> In order to scan, we need to have the radio on and we need to be able to send
    >> and receive. What are you gonna turn off?
    > The obvious route would be to power the card down, but come back up
    > every two minutes to perform a scan, or if userspace explicitly requests
    > one. Would this cause problems in some cases?

    I don't think it makes sense. For zd1211 the power consumption and heat
    emission goes up considerably when the interface is brought up (radio
    on, interrupts enabled, etc), and this is also a relatively long
    operation in terms of duration needed to bring the interface up and
    down. A scanning operation requires radio on, interrupts enabled, lots
    of register reading, RF calibration, RX/TX ringbuffers allocation, etc.

    I don't think that supporting scanning when the interface is supposed to
    be disabled is sensible. If you want to scan, you are simply sending and
    receiving frames, it's no different from having the interface up and
    sending/receiving data frames.

    There are additional implementation problems: scanning requires 2
    different ioctl calls: siwscan, then several giwscan. If you want the
    driver to effectively temporarily bring the interface up when userspace
    requests a scan but the interface was down, then how does the driver
    know when to bring it down again?

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      Last update: 2006-12-21 03:41    [W:0.042 / U:10.472 seconds]
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