Re: [Xen-devel] [PATCH RFC 4/8] ns16550: support DesignWare 8250

[Ian Campbell <Ian.Campbell@xxxxxxxxxx>]

On Tue, 2013-09-10 at 16:02 +0100, Jan Beulich wrote:
> >>> On 10.09.13 at 16:18, Ian Campbell <ian.campbell@xxxxxxxxxx> wrote:
> > @@ -233,6 +234,16 @@ static void ns16550_setup_preirq(struct ns16550 *uart)
> >      /* No interrupts. */
> >      ns_write_reg(uart, UART_IER, 0);
> >  
> > +    if ( uart->dw_usr_bsy &&
> > +         (ns_read_reg(uart, UART_IIR) & UART_IIR_BSY) == UART_IIR_BSY )
> > +    {
> > +        /* DesignWare 8250 detects if LCR is written while the UART is
> > +         * busy and raises a "busy detect" interrupt. Read the UART
> > +         * Status Register to clear this state.
> > +         */
> > +        (void)ns_read_reg(uart, UART_USR);
> 
> Pointless cast?

It's a hint to the compiler/reader that the return value is deliberately
discarded. We have a handful of these in the tree already.

Ian.


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