Delayed response to MBIM OPEN message
benchan at chromium.org
Wed Feb 19 09:56:13 PST 2014
On Wed, Feb 19, 2014 at 8:54 AM, Ben Chan <benchan at chromium.org> wrote:
> Hi Aleksander,
> libmbim currently retries the OPEN message
> (mbim-device.c:open_message) every 1s, if the modem does not respond.
> However, MS recommends delaying MBIM OPEN
> as follows:
> "MBIM devices may require time to complete initialization when they
> receive MBIM OPEN message from the host. The device should wait for
> its initialization to complete before responding to the MBIM OPEN
> message. The device should not respond to the message with error
> status like MBIM_STATUS_BUSY and expect the host to poll the device
> with MBIM OPEN messages. Responding to MBIM OPEN with a status other
> than MBIM_STATUS_SUCCESS terminates the initialization process on the
> From my observation, it looks like modem vendors follow this
> recommendation and delay the response to the OPEN message while the
> modem is still initializing. The initialization process gets
> unnecessarily terminated if libmbim retries the OPEN message too soon.
> Other than letting libmbim to wait (much) longer before retrying the
> OPEN message, I'm not sure if there is any better solution.
> How do you think?
As the transaction already has a timeout and a cancelable object, perhaps
we can simply increase the retry interval. I can help gather some data on
how long it takes for modems to initialize.
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