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Introduce serialport_write_nonblock()

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It seems useful to have a generic and platform-independent method to
read and write to a serial port without blocking. This is the write part.

This allows to get rid of the explicit temporary disabling of blocking I/O in
serprog's sp_synchronize().

Corresponding to flashrom svn r1662.

Signed-off-by: Stefan Tauner <stefan.tauner@alumni.tuwien.ac.at>
Acked-by: Stefan Tauner <stefan.tauner@alumni.tuwien.ac.at>
This commit is contained in:
Stefan Tauner 2013-04-01 00:45:45 +00:00
parent 00e1608501
commit ae3d83765c
3 changed files with 78 additions and 14 deletions
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1
programmer.h
View File

@ -660,6 +660,7 @@ extern fdtype sp_fd;
/* expose serialport_shutdown as it's currently used by buspirate */
int serialport_shutdown(void *data);
int serialport_write(unsigned char *buf, unsigned int writecnt);
int serialport_write_nonblock(unsigned char *buf, unsigned int writecnt, unsigned int timeout, unsigned int *really_wrote);
int serialport_read(unsigned char *buf, unsigned int readcnt);
int serialport_read_nonblock(unsigned char *c, unsigned int readcnt, unsigned int timeout, unsigned int *really_read);

72
serial.c
View File

@ -431,3 +431,75 @@ int serialport_read_nonblock(unsigned char *c, unsigned int readcnt, unsigned in
}
return ret;
}
/* Tries up to timeout ms to write writecnt characters from the array starting at buf. Returns
* 0 on success, positive values on temporary errors (e.g. timeouts) and negative ones on permanent errors.
* If really_wrote is not NULL, this function sets its contents to the number of bytes written successfully. */
int serialport_write_nonblock(unsigned char *buf, unsigned int writecnt, unsigned int timeout, unsigned int *really_wrote)
{
int ret = 1;
/* disable blocked i/o and declare platform-specific variables */
#ifdef _WIN32
DWORD rv;
COMMTIMEOUTS oldTimeout;
COMMTIMEOUTS newTimeout = {
.ReadIntervalTimeout = MAXDWORD,
.ReadTotalTimeoutMultiplier = 0,
.ReadTotalTimeoutConstant = 0,
.WriteTotalTimeoutMultiplier = 0,
.WriteTotalTimeoutConstant = 0
};
if(!GetCommTimeouts(sp_fd, &oldTimeout)) {
msg_perr_strerror("Could not get serial port timeout settings: ");
return -1;
}
if(!SetCommTimeouts(sp_fd, &newTimeout)) {
msg_perr_strerror("Could not set serial port timeout settings: ");
return -1;
}
#else
ssize_t rv;
const int flags = fcntl(sp_fd, F_GETFL);
fcntl(sp_fd, F_SETFL, flags | O_NONBLOCK);
#endif
int i;
int wr_bytes = 0;
for (i = 0; i < timeout; i++) {
msg_pspew("writecnt %d wr_bytes %d\n", writecnt, wr_bytes);
#ifdef _WIN32
WriteFile(sp_fd, buf + wr_bytes, writecnt - wr_bytes, &rv, NULL);
msg_pspew("wrote %lu bytes\n", rv);
#else
rv = write(sp_fd, buf + wr_bytes, writecnt - wr_bytes);
msg_pspew("wrote %zd bytes\n", rv);
#endif
if ((rv == -1) && (errno != EAGAIN)) {
msg_perr_strerror("Serial port write error: ");
ret = -1;
break;
}
if (rv > 0) {
wr_bytes += rv;
if (wr_bytes == writecnt) {
msg_pspew("write successful\n");
ret = 0;
break;
}
}
internal_delay(1000); /* 1ms units */
}
if (really_wrote != NULL)
*really_wrote = wr_bytes;
/* restore original blocking behavior */
#ifdef _WIN32
if (!SetCommTimeouts(sp_fd, &oldTimeout)) {
msg_perr_strerror("Could not restore serial port timeout settings: ");
#else
if (fcntl(sp_fd, F_SETFL, flags) != 0) {
#endif
return -1;
}
return ret;
}

19
serprog.c
View File

@ -117,23 +117,19 @@ static int sp_opensocket(char *ip, unsigned int port)
/* Synchronize: a bit tricky algorithm that tries to (and in my tests has *
* always succeeded in) bring the serial protocol to known waiting-for- *
* command state - uses nonblocking read - rest of the driver uses *
* command state - uses nonblocking I/O - rest of the driver uses *
* blocking read - TODO: add an alarm() timer for the rest of the app on *
* serial operations, though not such a big issue as the first thing to *
* do is synchronize (eg. check that device is alive). */
static int sp_synchronize(void)
{
int i;
int flags = fcntl(sp_fd, F_GETFL);
unsigned char buf[8];
flags |= O_NONBLOCK;
fcntl(sp_fd, F_SETFL, flags);
/* First sends 8 NOPs, then flushes the return data - should cause *
* the device serial parser to get to a sane state, unless if it *
* is waiting for a real long write-n. */
memset(buf, S_CMD_NOP, 8);
if (write(sp_fd, buf, 8) != 8) {
msg_perr("flush write: %s\n", strerror(errno));
if (serialport_write_nonblock(buf, 8, 1, NULL) != 0) {
goto err_out;
}
/* A second should be enough to get all the answers to the buffer */
@ -147,8 +143,7 @@ static int sp_synchronize(void)
for (i = 0; i < 8; i++) {
int n;
unsigned char c = S_CMD_SYNCNOP;
if (write(sp_fd, &c, 1) != 1) {
msg_perr("sync write: %s\n", strerror(errno));
if (serialport_write_nonblock(&c, 1, 1, NULL) != 0) {
goto err_out;
}
msg_pdbg(".");
@ -165,9 +160,8 @@ static int sp_synchronize(void)
if (ret > 0 || c != S_ACK)
continue;
c = S_CMD_SYNCNOP;
if (write(sp_fd, &c, 1) != 1) {
msg_perr("sync write: %s\n", strerror(errno));
return 1;
if (serialport_write_nonblock(&c, 1, 1, NULL) != 0) {
goto err_out;
}
ret = serialport_read_nonblock(&c, 1, 500, NULL);
if (ret < 0)
@ -179,9 +173,6 @@ static int sp_synchronize(void)
goto err_out;
if (c != S_ACK)
break; /* fail */
/* Ok, synchronized; back to blocking reads and return. */
flags &= ~O_NONBLOCK;
fcntl(sp_fd, F_SETFL, flags);
msg_pdbg("\n");
return 0;
}