--- On Thu, 5/13/10, Ron Madrid <ron_madrid@xxxxxxxxxxxxx> wrote: > From: Ron Madrid <ron_madrid@xxxxxxxxxxxxx> > Subject: Re: g_serial and cdc_acm communications > To: "Rob Duncan" <Robert.Duncan@xxxxxxxx> > Cc: "Oliver Neukum" <oliver@xxxxxxxxxx>, "linux-usb@xxxxxxxxxxxxxxx" <linux-usb@xxxxxxxxxxxxxxx> > Date: Thursday, May 13, 2010, 2:03 PM > --- On Thu, 5/13/10, Ron Madrid > <ron_madrid@xxxxxxxxxxxxx> > wrote: > > > From: Ron Madrid <ron_madrid@xxxxxxxxxxxxx> > > Subject: Re: g_serial and cdc_acm communications > > To: "Rob Duncan" <Robert.Duncan@xxxxxxxx> > > Cc: "Oliver Neukum" <oliver@xxxxxxxxxx>, > "linux-usb@xxxxxxxxxxxxxxx" > <linux-usb@xxxxxxxxxxxxxxx> > > Date: Thursday, May 13, 2010, 12:13 PM > > --- On Thu, 5/13/10, Rob Duncan > > <Robert.Duncan@xxxxxxxx> > > wrote: > > > > > From: Rob Duncan <Robert.Duncan@xxxxxxxx> > > > Subject: Re: g_serial and cdc_acm communications > > > To: "Ron Madrid" <ron_madrid@xxxxxxxxxxxxx> > > > Cc: "Oliver Neukum" <oliver@xxxxxxxxxx>, > > "linux-usb@xxxxxxxxxxxxxxx" > > <linux-usb@xxxxxxxxxxxxxxx> > > > Date: Thursday, May 13, 2010, 11:49 AM > > > > > > On May 13, 2010, at 10:11 AM, Ron Madrid wrote: > > > > > > > This is the last (failing) transfer that > occurs. > > > > > The third > > > > line is my app receiving information about > the > > data it > > > should > > > > expect, and the size of the transfer in > dwords, > > 0x7d0 > > > (8000 > > > > bytes). I then see, in subsequent > lines, 7 > > * > > > 1024 bytes > > > > received (Bi) followed by 832 bytes > received > > which > > > totals up > > > > to 8000 bytes. > > > > > > I suspect it's because that host controller is > waiting > > for > > > the end of > > > the transfer. 832 bytes is an exact > multiple of > > > 64-bytes, which means > > > that the the HC is waiting for a short packet, or > up > > to > > > your transfer > > > size, which appears to be 1024. > > > > I'm read()ing 8000 bytes. I just tried read()ing > 8004 > > bytes > > and I saw a similar failure. Also, this > 8000/8004 > > byte read() > > is in a 10000 iteration loop and is successful a > seemingly > > arbitrary number of times (a few dozen to a few > hundred) > > before failing. I had read about a zpl problem > > before, but > > this doesn't seem to be the case unless I'm missing > > something. > > Another wrinkle in all of this ... I just tried write()ing > the exact same number of bytes and everything appeared to > work flawlessly. I noticed that when I was doing write() to the tty device, the USB device was performing Bo with 512 bytes at a time, read() seemed to do 1024 at a time. Is there a way that I could change the USB Bi buffer to 512 and see if that fixes anything? Or does this possible mean anything? Ron -- To unsubscribe from this list: send the line "unsubscribe linux-usb" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
