We can know about status stage response from USB1.1 spec (8.5.2.1
Reporting Status Results):
/------------------------------------------------------------------------------/
For control writes, the host sends an IN token to the control pipe to
initiate the Status stage. The function
responds with either a handshake or a zero-length data packet to
indicate its current status. NAK indicates
that the function is still processing the command and that the host
should continue the Status stage; return
of a zero-length packet indicates normal completion of the command; and
STALL indicates that the
function cannot complete the command. The function expects the host to
respond to the data packet in the
Status stage with ACK. If the function does not receive ACK, it remains
in the Status stage of the
command and will continue to return the zero-length data packet for as
long as the host continues to send
IN tokens.
/------------------------------------------------------------------------------/
but we can't see how usb device module can responds with either NAK or
STALL from omap_udc.c or other udc driver.
In omap_udc.c/ep0_irq:
... ...
if (irq_src & UDC_EP0_RX) {
... ...
if (stat & UDC_ACK) {
... ...
if (!udc->ep0_in) {
... ...
stat = read_fifo(ep0, req);
... ...
/* activate status stage */
if (stat == 1) {
done(ep0, req, 0);
/* that may have STALLed ep0... */
UDC_EP_NUM_REG = UDC_EP_SEL|UDC_EP_DIR;
UDC_CTRL_REG = UDC_CLR_EP;
UDC_CTRL_REG = UDC_SET_FIFO_EN;
/* causing ACK handshaking by setting the */
* CTRL.SET_FIFO_EN bit with an empty */
* endpoint 0 FIFO. */
*/
UDC_EP_NUM_REG = UDC_EP_DIR;
udc->ep0_pending = 0;
}
... ...
}
... ...
}
... ...
}
... ...
so, when the function is still busy completing command or the command
sequence failed to complete, how do gadget driver tell udc to response
Control writes with NAK/STALL?
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