Re: [PATCH] serial: Do not treat the IIR register as a bitfield

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

 



While you're fixing this, there's a bug in samples/vfio-mdev/mtty.c:

		u8 ier = mdev_state->s[index].uart_reg[UART_IER];
		*buf = 0;

		mutex_lock(&mdev_state->rxtx_lock);
		/* Interrupt priority 1: Parity, overrun, framing or break */
		if ((ier & UART_IER_RLSI) && mdev_state->s[index].overrun)
			*buf |= UART_IIR_RLSI;

		/* Interrupt priority 2: Fifo trigger level reached */
		if ((ier & UART_IER_RDI) &&
		    (mdev_state->s[index].rxtx.count ==
		      mdev_state->s[index].intr_trigger_level))
			*buf |= UART_IIR_RDI;

		/* Interrupt priotiry 3: transmitter holding register empty */
		if ((ier & UART_IER_THRI) &&
		    (mdev_state->s[index].rxtx.head ==
				mdev_state->s[index].rxtx.tail))
			*buf |= UART_IIR_THRI;

		/* Interrupt priotiry 4: Modem status: CTS, DSR, RI or DCD  */
		if ((ier & UART_IER_MSI) &&
		    (mdev_state->s[index].uart_reg[UART_MCR] &
				 (UART_MCR_RTS | UART_MCR_DTR)))
			*buf |= UART_IIR_MSI;

		/* bit0: 0=> interrupt pending, 1=> no interrupt is pending */
		if (*buf == 0)
			*buf = UART_IIR_NO_INT;

It's treating the UART_IIR_* fields as a bitmask which is bad enough,
but in the "Interrupt priority 4" case, UART_IIR_MSI is zero, so 
"*buf |= UART_IIR_MSI" is a no-op.   And in the case where the modem
status interrupt is the only thing set, *buf will be 0, and UART_IIR_NO_INT
gets set erroneously.

So this is another example of the bug of trying to treat the
UART_IIR_* fields as a bitmask....

Yes, it's only sample code, but best fix it now before it gets copied
elsewhere and metastisizes.   :-)

							- Ted
							
--
To unsubscribe from this list: send the line "unsubscribe linux-tegra" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html



[Index of Archives]     [ARM Kernel]     [Linux ARM]     [Linux ARM MSM]     [Linux USB Devel]     [Video for Linux]     [Linux Audio Users]     [Yosemite News]     [Linux Kernel]     [Linux SCSI]

  Powered by Linux