Re: [PATCH-for-5.2?] hw/char/serial: Clean up unnecessary code

[Paolo Bonzini]

On 20/11/20 17:19, Philippe Mathieu-Daudé wrote:
> Since commit 5ec3a23e6c8 ("serial: convert PIO to new memory
> api read/write") we don't need to worry about accesses bigger
> than 8-bit. Use the extract()/deposit() functions to access
> the correct part of the 16-bit 'divider' register.
>
> Reported-by: Jonathan D. Belanger <jbelanger1@rochester.rr.com>
> Buglink: https://bugs.launchpad.net/qemu/+bug/1904331
> Signed-off-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
> ---
> Cc: Bug 1904331 <1904331@bugs.launchpad.net>
> ---
>   hw/char/serial.c | 13 +++++--------
>   1 file changed, 5 insertions(+), 8 deletions(-)

Looks good, but certainly not for 5.2.

Paolo

> diff --git a/hw/char/serial.c b/hw/char/serial.c
> index 97f71879ff2..62c627f486f 100644
> --- a/hw/char/serial.c
> +++ b/hw/char/serial.c
> @@ -24,6 +24,7 @@
>    */
>   
>   #include "qemu/osdep.h"
> +#include "qemu/bitops.h"
>   #include "hw/char/serial.h"
>   #include "hw/irq.h"
>   #include "migration/vmstate.h"
> @@ -338,11 +339,7 @@ static void serial_ioport_write(void *opaque, hwaddr addr, 
> uint64_t val,
>       default:
>       case 0:
>           if (s->lcr & UART_LCR_DLAB) {
> -            if (size == 1) {
> -                s->divider = (s->divider & 0xff00) | val;
> -            } else {
> -                s->divider = val;
> -            }
> +            s->divider = deposit32(s->divider, 8 * addr, 8, val);
>               serial_update_parameters(s);
>           } else {
>               s->thr = (uint8_t) val;
> @@ -364,7 +361,7 @@ static void serial_ioport_write(void *opaque, hwaddr addr, 
> uint64_t val,
>           break;
>       case 1:
>           if (s->lcr & UART_LCR_DLAB) {
> -            s->divider = (s->divider & 0x00ff) | (val << 8);
> +            s->divider = deposit32(s->divider, 8 * addr, 8, val);
>               serial_update_parameters(s);
>           } else {
>               uint8_t changed = (s->ier ^ val) & 0x0f;
> @@ -478,7 +475,7 @@ static uint64_t serial_ioport_read(void *opaque, hwaddr 
> addr, unsigned size)
>       default:
>       case 0:
>           if (s->lcr & UART_LCR_DLAB) {
> -            ret = s->divider & 0xff;
> +            ret = extract16(s->divider, 8 * addr, 8);
>           } else {
>               if(s->fcr & UART_FCR_FE) {
>                   ret = fifo8_is_empty(&s->recv_fifo) ?
> @@ -502,7 +499,7 @@ static uint64_t serial_ioport_read(void *opaque, hwaddr 
> addr, unsigned size)
>           break;
>       case 1:
>           if (s->lcr & UART_LCR_DLAB) {
> -            ret = (s->divider >> 8) & 0xff;
> +            ret = extract16(s->divider, 8 * addr, 8);
>           } else {
>               ret = s->ier;
>           }