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

[Ian Campbell <Ian.Campbell@xxxxxxxxxx>]

On Tue, 2013-09-10 at 16:28 +0100, Jan Beulich wrote:
> >>> On 10.09.13 at 17:21, Ian Campbell <Ian.Campbell@xxxxxxxxxx> wrote:
> > On Tue, 2013-09-10 at 16:19 +0100, Jan Beulich wrote:
> >> >>> On 10.09.13 at 17:12, Ian Campbell <Ian.Campbell@xxxxxxxxxx> wrote:
> >> > 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.
> >> 
> >> And over time I managed to remove another handful...
> > 
> > Well, I guess I don't mind one way or another. What's the problem with
> > them?
> 
> I'm viewing casts as dangerous in general, and hence advocate
> for removing them wherever not really needed. Casts to void I
> view as warranted only when needed to silence false positive
> compiler warnings.
> 
> And in the case here: Ignoring function return values isn't that
> uncommon. And the comment already explains why the call is
> being made.

OK, I'll drop it then.



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