soft_uart: check Rx/Tx state once in osmo_soft_uart_{rx,tx}_ubits()
Check it once rather than doing this in a loop. Return -EAGAIN if
Rx or Tx is not enabled when calling osmo_soft_uart_{rx,tx}_ubits().
This [theoretically] improves performance by reducing the number of
conditional statements in loops. In the Tx path, this also prevents
calling the .tx_cb() when the transmitter is disabled, so that we
don't loose the application data.
Change-Id: I70f93b3655eb21c2323e451052c40cd305c016c8
Related: OS#4396
diff --git a/src/core/soft_uart.c b/src/core/soft_uart.c
index 8d9142b..8cf45e1 100644
--- a/src/core/soft_uart.c
+++ b/src/core/soft_uart.c
@@ -111,9 +111,6 @@
/* receive a single bit */
static inline void osmo_uart_rx_bit(struct osmo_soft_uart *suart, const ubit_t bit)
{
- if (!suart->rx.running)
- return;
-
switch (suart->rx.flow_state) {
case SUART_FLOW_ST_IDLE:
if (bit == 0) { /* start bit condition */
@@ -196,9 +193,12 @@
* \param[in] suart soft-UART instance to feed bits into.
* \param[in] ubits pointer to the unpacked bits.
* \param[in] n_ubits number of unpacked bits to be fed.
- * \returns 0 on success; negative on error. */
+ * \returns 0 on success; negative on error.
+ * -EAGAIN indicates that the receiver is disabled. */
int osmo_soft_uart_rx_ubits(struct osmo_soft_uart *suart, const ubit_t *ubits, size_t n_ubits)
{
+ if (!suart->rx.running)
+ return -EAGAIN;
for (size_t i = 0; i < n_ubits; i++)
osmo_uart_rx_bit(suart, ubits[i]);
return 0;
@@ -213,9 +213,6 @@
{
ubit_t tx_bit = 1;
- if (!suart->tx.running)
- return tx_bit;
-
switch (suart->tx.flow_state) {
case SUART_FLOW_ST_IDLE:
if (msg && msgb_length(msg) > 0) { /* if we have pending data */
@@ -280,7 +277,8 @@
* \param[in] suart soft-UART instance to pull the bits from.
* \param[out] ubits pointer to a buffer where to store pulled bits.
* \param[in] n_ubits number of unpacked bits to be pulled.
- * \returns 0 on success; negative on error. */
+ * \returns 0 on success; negative on error.
+ * -EAGAIN indicates that the transmitter is disabled. */
int osmo_soft_uart_tx_ubits(struct osmo_soft_uart *suart, ubit_t *ubits, size_t n_ubits)
{
const struct osmo_soft_uart_cfg *cfg = &suart->cfg;
@@ -290,6 +288,9 @@
if (OSMO_UNLIKELY(n_ubits == 0))
return -EINVAL;
+ if (!suart->tx.running)
+ return -EAGAIN;
+
/* calculate UART frame size for the effective config */
n_frame_bits = 1 + cfg->num_data_bits + cfg->num_stop_bits;
if (cfg->parity_mode != OSMO_SUART_PARITY_NONE)
diff --git a/tests/soft_uart/soft_uart_test.c b/tests/soft_uart/soft_uart_test.c
index 522739a..276ffe1 100644
--- a/tests/soft_uart/soft_uart_test.c
+++ b/tests/soft_uart/soft_uart_test.c
@@ -16,6 +16,7 @@
*
*/
+#include <errno.h>
#include <stdio.h>
#include <stdint.h>
@@ -256,10 +257,18 @@
{
struct osmo_soft_uart_cfg cfg;
struct osmo_soft_uart *suart;
+ int rc;
suart = osmo_soft_uart_alloc(NULL, __func__, &suart_test_default_cfg);
OSMO_ASSERT(suart != NULL);
+ /* expect -EAGAIN when the transmitter is not enabled */
+ rc = osmo_soft_uart_tx_ubits(suart, NULL, 42);
+ OSMO_ASSERT(rc == -EAGAIN);
+ /* expect -EAGAIN when the receiver is not enabled */
+ rc = osmo_soft_uart_rx_ubits(suart, NULL, 42);
+ OSMO_ASSERT(rc == -EAGAIN);
+
osmo_soft_uart_set_tx(suart, true);
osmo_soft_uart_set_rx(suart, true);