Thanks. I looked my code again, which is modified from example
cross-link.c. The section looks like:

...
                 irq_time = rx_event.rxpend_timestamp;
                read = rt_dev_read(read_fd, &write_time, sz);
                if (read == sz) {
                        read_time = rt_timer_read();
                        printf("%3d |%16llu |%16llu |%16llu\n", nr,
                               irq_time  - write_time,
                               read_time - irq_time,
                               read_time - write_time);
                        nr++;
                } else if (read < 0 ) {
                        printf(RTASK_PREFIX "error on rt_dev_read, code %s\n",
                               strerror(-err)); <<<<<<<===========
                        break;
                } else {
                        printf(RTASK_PREFIX "only %d / %d byte received \n",
                               read, sz);
                        break;
                }
...
I guess I should change the strerror(-err) to strerror(-read). If I do
that, I some
times get a " code input/output error". That is better. What can cause
input/output error? I get my serial port in that state consistently
when I
finish running my GPS program. I can reset it to a usable serial port
again by remove and re-load xeno-16550A module. But setserial -G can't
see anything unusual. Could it be some unclosed serial port?

My simple code is attached.

Thanks,

Everett







On Sat, Jun 12, 2010 at 5:31 PM, Gilles Chanteperdrix
<gilles.chanteperdrix@xenomai.org> wrote:
> Everett Wang wrote:
>> Hi,
>>
>> I am developing a real time programming using xenomai, RTDM. When
>> I try to read serial port, I sometimes get this message:
>>
>> error on rt_dev_read, code Success
>>
>> I checked my program and found that when rt_dev_read returns a
>> negative number, this message is printed. What does this error message
>> mean? It seems that my port is open when I tried to read from it.
>
> It means that you are probably using errno, and since rt_dev_read does
> not set errno, you get "Success" as error message instead of the real
> error message. If you want to print the real error message, you should
> use strerror(-rc) where rc is the return code of rt_dev_read.
>
> But of course, I am just guessing here, seeing your test code would help
> more.
>
>
> --
>                                            Gilles.
>