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trezorhal/usb: do not send full packets

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This commit is contained in:
Jan Pochyla 2017-05-24 13:46:28 +02:00
parent f7d72741fd
commit ecd5fd858b
1 changed files with 3 additions and 2 deletions
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5
micropython/trezorhal/usb_vcp-impl.h
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@ -408,8 +408,9 @@ static uint8_t usb_vcp_class_sof(USBD_HandleTypeDef *dev, usb_vcp_state_t *state
// Read from the tx ring buffer
usb_rbuf_t *b = &state->tx_ring;
uint8_t *buf = state->tx_packet;
size_t len = state->max_packet_len;
size_t mask = b->cap - 1;
// We avoid sending full packets as they stall the hosts pipeline, see:
// <http://www.cypress.com/?id=4&rID=92719>
size_t len = state->max_packet_len - 1;
size_t i;
for (i = 0; (i < len) && !ring_empty(b); i++) {
buf[i] = b->buf[b->read & mask];