Messages in this thread | | | Date | Tue, 28 Dec 2010 07:15:35 -0800 (PST) | From | Tsozik <> | Subject | Re: [PATCH 1/1] mct_u232: added _ioctl, _msr_to_icount and _get_icount functions |
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Greg,
I'm sorry to bother you again, but I'm wondering if you could comment on Pete's concern below.
Thank you in advance for your expertise on the matter, Vadim.
--- On Tue, 12/28/10, Pete Zaitcev <zaitcev@redhat.com> wrote:
> From: Pete Zaitcev <zaitcev@redhat.com> > Subject: Re: [PATCH 1/1] mct_u232: added _ioctl, _msr_to_icount and _get_icount functions > To: "Tsozik" <tsozik@yahoo.com> > Cc: "Greg Kroah-Hartman" <gregkh@suse.de>, linux-usb@vger.kernel.org, linux-kernel@vger.kernel.org, zaitcev@redhat.com > Date: Tuesday, December 28, 2010, 1:40 AM > On Mon, 27 Dec 2010 20:04:51 -0800 > (PST) > Tsozik <tsozik@yahoo.com> > wrote: > > > So I ran geiger counter against /dev/ttyS0 device for > 20 minutes and > > acquired 20 measurements. Then I compared last average > with last 20 > > minute measurement average acquired via mct_u232 on > the laptop placed > > nearby. The error was ~4% (rounded up). > > Great, I'm ready to ack. > > There's just one thing that is bugging me... I think it > would be best > if Alan Cox or Greg Kroah commented on it. The edgeport > does the > following, which we copied: > > > schedule(); > ........ > if (cnow.rng == > cprev.rng && cnow.dsr == cprev.dsr && > > cnow.dcd == cprev.dcd && cnow.cts == cprev.cts) > > return -EIO; /* no change => error */ > if (((arg & > TIOCM_RNG) && (cnow.rng != cprev.rng)) || > ((arg > & TIOCM_DSR) && (cnow.dsr != cprev.dsr)) || > ((arg > & TIOCM_CD) && (cnow.dcd != cprev.dcd)) > || > ((arg > & TIOCM_CTS) && (cnow.cts != cprev.cts))) { > > return 0; > } > > So, if there was a status report, but no change to bits, > the ioctl > TIOCMIWAIT would return with -EIO. In serial_core.c, that > serves > conventional non-USB UARTs, nothing like this occurs. I am > not quite > sure what the point of doing this -EIO check is. > > Oh and BTW, I'm wondering what is going to happen if the > device is > disconnected while an application is blocked waiting for > the status > change. The patch is not particularly bad here, it just > copies > an existing code from elsewhere. > > -- Pete >
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