[flashrom] [PATCH] Combine serialport_write and serialport_read into serialport_rw.
Carl-Daniel Hailfinger
c-d.hailfinger.devel.2006 at gmx.net
Fri May 31 00:36:17 CEST 2013
Am 01.04.2013 03:14 schrieb Stefan Tauner:
> Because they share almost all code, combine them into serialport_rw
> and export the old functions as wrappers. This makes reads "empty reads"-
> aware and programmers able to detect such problems even on "blocking"
> reads.
>
> Signed-off-by: Stefan Tauner <stefan.tauner at student.tuwien.ac.at>
Acked-by: Carl-Daniel Hailfinger <c-d.hailfinger.devel.2006 at gmx.net>
> diff --git a/serial.c b/serial.c
> index 49484f5..6679b7c 100644
> --- a/serial.c
> +++ b/serial.c
> @@ -28,6 +28,7 @@
> #include <sys/stat.h>
> #include <errno.h>
> #include <inttypes.h>
> +#include <stdbool.h>
> #ifdef _WIN32
> #include <conio.h>
> #else
> @@ -328,68 +329,61 @@ int serialport_shutdown(void *data)
> return 0;
> }
>
> -int serialport_write(unsigned char *buf, unsigned int writecnt)
> +/* Writes (if \c outdir is true) or reads \c todo bytes from/into \c buf.
> + * Tries up to 10 times with a timeout of \c ms ms between each try. */
> +static int serialport_rw(unsigned char *buf, unsigned int todo, bool outdir, unsigned int ms)
> {
> + const char * const op = outdir ? "write" : "read";
> #ifdef _WIN32
> - DWORD tmp = 0;
> + DWORD cur = 0;
> #else
> - ssize_t tmp = 0;
> + ssize_t cur = 0;
> #endif
> - unsigned int empty_writes = 250; /* results in a ca. 125ms timeout */
> + unsigned int empty_tries = 10;
>
> - while (writecnt > 0) {
> + while (todo > 0) {
> #ifdef _WIN32
> - WriteFile(sp_fd, buf, writecnt, &tmp, NULL);
> + if (outdir)
> + WriteFile(sp_fd, buf, todo, &cur, NULL);
> + else
> + ReadFile(sp_fd, buf, todo, &cur, NULL);
> #else
> - tmp = write(sp_fd, buf, writecnt);
> + if (outdir)
> + cur = write(sp_fd, buf, todo);
> + else
> + cur = read(sp_fd, buf, todo);
> #endif
> - if (tmp == -1) {
> - msg_perr("Serial port write error!\n");
> + if (cur == -1) {
> + msg_perr("Serial port %s error!\n", op);
> return 1;
The logic of error handling is non-portable (AFAICS the number of
read/written bytes for the error case is 0 on Windows and -1 on POSIX).
That said, it was non-portable before, so this patch doesn't change it
for the worse.
> }
> - if (!tmp) {
> - msg_pdbg2("Empty write\n");
> - empty_writes--;
> - programmer_delay(500);
> - if (empty_writes == 0) {
> + if (cur == 0) {
> + msg_pdbg2("Empty %s.\n", op);
> + empty_tries--;
> + programmer_delay(ms * 1000);
> + if (empty_tries == 0) {
> msg_perr("Serial port is unresponsive!\n");
That message is actually wrong for the read case. If the serial device
(e.g. Bus Pirate) disappears, you'll get 0-byte reads forever, at least
on Linux. AFAICS blocking reads shall either return an error or at least
1 byte. That rule seems to be valid on Linux and Windows. Errors can be
transient, though (see EINTR and other fun stuff).
Suggested alternative wording: "Serial port is unresponsive or disappeared"
> return 1;
> }
> }
> - writecnt -= tmp;
> - buf += tmp;
> + todo -= cur;
> + buf += cur;
> }
>
> return 0;
> }
>
> -int serialport_read(unsigned char *buf, unsigned int readcnt)
> +int serialport_write(unsigned char *buf, unsigned int writecnt)
> {
> -#ifdef _WIN32
> - DWORD tmp = 0;
> -#else
> - ssize_t tmp = 0;
> -#endif
> -
> - while (readcnt > 0) {
> -#ifdef _WIN32
> - ReadFile(sp_fd, buf, readcnt, &tmp, NULL);
> -#else
> - tmp = read(sp_fd, buf, readcnt);
> -#endif
> - if (tmp == -1) {
> - msg_perr("Serial port read error!\n");
> - return 1;
> - }
> - if (!tmp)
> - msg_pdbg2("Empty read\n");
> - readcnt -= tmp;
> - buf += tmp;
> - }
> + return serialport_rw(buf, writecnt, true, 1);
> +}
>
> - return 0;
> +int serialport_read(unsigned char *buf, unsigned int readcnt)
> +{
> + return serialport_rw(buf, readcnt, false, 10);
> }
>
> +
> /* Tries up to timeout ms to read readcnt characters and places them into the array starting at c. Returns
> * 0 on success, positive values on temporary errors (e.g. timeouts) and negative ones on permanent errors.
> * If really_read is not NULL, this function sets its contents to the number of bytes read successfully. */
Regards,
Carl-Daniel
--
http://www.hailfinger.org/
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