Date: Wed, 25 Jun 2003 14:58:28 -0400 From: "Louis A. Mamakos" <louie@TransSys.COM> To: "M. Warner Losh" <imp@bsdimp.com> Cc: freebsd-hackers@freebsd.org Subject: Re: USB, select/poll for ucom Message-ID: <200306251858.h5PIwSW8017536@whizzo.transsys.com> In-Reply-To: Your message of "Wed, 25 Jun 2003 10:15:49 MDT." <20030625.101549.78767546.imp@bsdimp.com> References: <imp@bsdimp.com> <E19VCk7-000254-00@cs.huji.ac.il> <20030625.101549.78767546.imp@bsdimp.com>
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> In message: <E19VCk7-000254-00@cs.huji.ac.il> > Danny Braniss <danny@cs.huji.ac.il> writes: > : > : > I'm able to use ppp with umodem/ucom. My brother uses ulpcom/ucom for > : > his ppp needs. I'm pretty sure that select is involved. :-) > : > > : > >From what I can see in the code, I'd expect that it would work because > : > the ttypoll routine is specified for the poll routine. Why do you > : > think it wouldn't work? > : > : well, for one, my program doesn't work :-), it works with the RS232 version. > : > : so i started to poke around, and did some reading, and as far as i could tell, > : the read(2) has to be initiated by the host, but my knowledge of usb is close > : to zero - it was zero 2 days ago, but still looking for some better docs, and > : polish my english - as far as i remember interrupt is not polling, but the > : ohci docs imply that :-) > > 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. I think the problem is that the USB hardware doesn't try to read data from the peripheral until the user-mode code does a read(2) system call. I had this problem with the ugen device. I would guess that the ucom/umodem devices could use the tty clist infrastructure as the intermediate buffer for data to be stuck into absent the user application doing a read. louie
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