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linux: detect port disconnection during Read

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See https://stackoverflow.com/a/34945814/1655275

> pselect signals that file descriptor is ready and
> ioctl(fd, FIONREAD, &len) returns zero len.

Failure to detect this condition has been revealed by
the testsuite:

=== RUN   TestDisconnectingPortDetection
2017/07/27 13:56:37 PR - Connecting to Probe
2017/07/27 13:56:37      > Searching for port 2341:8037
2017/07/27 13:56:37        Detected port '/dev/ttyACM0' 2341:8037
2017/07/27 13:56:37        Using '/dev/ttyACM0'
2017/07/27 13:56:37 Starting test (timeout 20s)
2017/07/27 13:56:37 PR - Turn ON target
2017/07/27 13:56:37 TR - Connecting to Target
2017/07/27 13:56:37      > Searching for port 2341:8036
2017/07/27 13:56:37        Detected port '/dev/ttyACM0' 2341:8037
[...cut...]
2017/07/27 13:56:46      > Searching for port 2341:8036
2017/07/27 13:56:46        Detected port '/dev/ttyACM0' 2341:8037
2017/07/27 13:56:46        Detected port '/dev/ttyACM1' 2341:8036
2017/07/27 13:56:46        Using '/dev/ttyACM1'
2017/07/27 13:56:46 T2 - Make a Read call
2017/07/27 13:56:46 T1 - Delay 200ms before disconnecting target
2017/07/27 13:56:46 T1 - Disconnect target
2017/07/27 13:56:46 PR - Turn OFF target
2017/07/27 13:56:46 T2 - Read returned: n=0 err=nil
--- FAIL: TestDisconnectingPortDetection (9.18s)
        Error Trace:    serial_test.go:100
	Error:		An error is expected but got nil. %s
	Messages:	Read returned no errors

this commit fix the problem above.
This commit is contained in:
Cristian Maglie
2017-07-27 13:53:59 +02:00
parent f355dbf608
commit a63b28875f
1 changed files with 6 additions and 0 deletions
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6
serial_unix.go
View File

@@ -77,6 +77,12 @@ func (port *unixPort) Read(p []byte) (int, error) {
if err == unix.EINTR {
continue
}
// Linux: when the port is disconnected during a read operation
// the port is left in a "readable with zero-length-data" state.
// https://stackoverflow.com/a/34945814/1655275
if n == 0 && err == nil {
return 0, &PortError{code: PortClosed}
}
if n < 0 { // Do not return -1 unix errors
n = 0
}