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usb: cdc_acm: rework cdc_acm_poll_out to non-blocking

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Change cdc_acm_poll_out to do the best to mimic behavior
of a hardware UART controller without flow control.

With this patch, if the USB subsystem is not ready,
no data is transfered to the buffer, that is, new character
is dropped. If the USB subsystem is ready and the buffer is full,
the first character from the tx_ringbuf is removed to
make room for the new character.

Signed-off-by: Johann Fischer <johann.fischer@nordicsemi.no>
This commit is contained in:
Johann Fischer 2021-08-06 16:33:17 +02:00 committed by Christopher Friedt
parent 4d3d734ffd
commit 37f4d9ba63
1 changed files with 26 additions and 12 deletions
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38
subsys/usb/class/cdc_acm.c
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@ -96,7 +96,6 @@ struct cdc_acm_dev_data_t {
/* Callback function pointer/arg */
uart_irq_callback_user_data_t cb;
void *cb_data;
struct k_sem poll_wait_sem;
struct k_work cb_work;
#if defined(CONFIG_CDC_ACM_DTE_RATE_CALLBACK_SUPPORT)
cdc_dte_rate_callback_t rate_cb;
@ -211,8 +210,6 @@ static void cdc_acm_write_cb(uint8_t ep, int size, void *priv)
dev_data->tx_ready = true;
k_sem_give(&dev_data->poll_wait_sem);
/* Call callback only if tx irq ena */
if (dev_data->cb && dev_data->tx_irq_ena) {
k_work_submit_to_queue(&USB_WORK_Q, &dev_data->cb_work);
@ -326,7 +323,6 @@ static void cdc_acm_int_in(uint8_t ep, enum usb_dc_ep_cb_status_code ep_status)
static void cdc_acm_reset_port(struct cdc_acm_dev_data_t *dev_data)
{
k_sem_give(&dev_data->poll_wait_sem);
dev_data->configured = false;
dev_data->suspended = false;
dev_data->rx_ready = false;
@ -473,7 +469,6 @@ static int cdc_acm_init(const struct device *dev)
LOG_DBG("Device dev %p dev_data %p cfg %p added to devlist %p",
dev, dev_data, dev->config, &cdc_acm_data_devlist);
k_sem_init(&dev_data->poll_wait_sem, 0, K_SEM_MAX_LIMIT);
k_work_init(&dev_data->cb_work, cdc_acm_irq_callback_work_handler);
k_work_init(&dev_data->tx_work, tx_work_handler);
@ -902,16 +897,35 @@ static int cdc_acm_poll_in(const struct device *dev, unsigned char *c)
/*
* @brief Output a character in polled mode.
*
* The UART poll method for USB UART is simulated by waiting till
* we get the next BULK In upcall from the USB device controller or 100 ms.
* The poll function looks similar to cdc_acm_fifo_fill() and
* tries to do the best to mimic behavior of a hardware UART controller
* without flow control.
* This function does not block, if the USB subsystem
* is not ready, no data is transferred to the buffer, that is, c is dropped.
* If the USB subsystem is ready and the buffer is full, the first character
* from the tx_ringbuf is removed to make room for the new character.
*/
static void cdc_acm_poll_out(const struct device *dev,
unsigned char c)
static void cdc_acm_poll_out(const struct device *dev, unsigned char c)
{
struct cdc_acm_dev_data_t * const dev_data = DEV_DATA(dev);
struct cdc_acm_dev_data_t * const dev_data = dev->data;
cdc_acm_fifo_fill(dev, &c, 1);
k_sem_take(&dev_data->poll_wait_sem, K_MSEC(100));
if (!dev_data->configured || dev_data->suspended) {
LOG_INF("USB device not ready, drop data");
return;
}
dev_data->tx_ready = false;
if (!ring_buf_put(dev_data->tx_ringbuf, &c, 1)) {
LOG_INF("Ring buffer full, drain buffer");
if (!ring_buf_get(dev_data->tx_ringbuf, NULL, 1) ||
!ring_buf_put(dev_data->tx_ringbuf, &c, 1)) {
LOG_ERR("Failed to drain buffer");
return;
}
}
k_work_submit_to_queue(&USB_WORK_Q, &dev_data->tx_work);
}
static const struct uart_driver_api cdc_acm_driver_api = {