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stm32/usbd_hid_interface: Address possible race condition vs. interrupt.

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The USB IRQ may fire once USBD_HID_ClearNAK() is called and then change the
last_read_len value.
This commit is contained in:
Peter D. Gray 2018-05-11 11:40:04 -04:00 committed by Damien George
parent 1f1623d3b7
commit ca36645410
1 changed files with 3 additions and 2 deletions
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5
ports/stm32/usbd_hid_interface.c
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@ -94,12 +94,13 @@ int usbd_hid_rx(usbd_hid_itf_t *hid, size_t len, uint8_t *buf, uint32_t timeout)
} }
// Copy bytes from device to user buffer // Copy bytes from device to user buffer
memcpy(buf, hid->buffer[hid->current_read_buffer], hid->last_read_len); int read_len = hid->last_read_len;
memcpy(buf, hid->buffer[hid->current_read_buffer], read_len);
hid->current_read_buffer = !hid->current_read_buffer; hid->current_read_buffer = !hid->current_read_buffer;
// Clear NAK to indicate we are ready to read more data // Clear NAK to indicate we are ready to read more data
USBD_HID_ClearNAK(hid->usbd); USBD_HID_ClearNAK(hid->usbd);
// Success, return number of bytes read // Success, return number of bytes read
return hid->last_read_len; return read_len;
} }