Re: USB, select/poll for ucom

From: Bernd Walter (ticso_at_cicely12.cicely.de)
Date: 06/28/03

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    Date: Sat, 28 Jun 2003 14:03:16 +0200
To: Danny Braniss <danny@cs.huji.ac.il>

    On Sat, Jun 28, 2003 at 12:37:10PM +0300, Danny Braniss wrote:
    > [...]
    > > have fun. the mindshare book is good. however, it took me a long
    > > time to get a usb 'aha' moment and understand its twisty maze was
    > > really a workable design obscured by standardese... I suspect it is a
    > > problem in the usb chipset driver for the com part. ttypoll just says
    > > 'you have data in the buffer' so for some reason the data isn't making
    > > into the tty buffer.
    > >
    > > Warner
    >
    > Im amazed at how some of you can write a driver based on the Spec. Docs!
    >
    > here is a pearl i came across reading the USB spec for 1.1, page 43
    >
    > 'The maximum allowable interrupt data payload
    > size is 64 bytes or less for full-speed.'

    The device will tell you his personal limits for the given endpoint.
    See wMaxPacketSize in usb_endpoint_descriptor_t.
    The specs only tell you that a device can't tell >64 byte as the
    maximum for an interrupt endpoint. 

    -- 
B.Walter                   BWCT                http://www.bwct.de
ticso@bwct.de                                  info@bwct.de
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