Re: [Qemu-devel] [PATCH] CMOS file support

[Anthony Liguori]

On 09/16/2010 08:58 AM, Mathias Krause wrote:
> In contrast to the BIOS and Option ROMs the CMOS content cannot be
> predefined by the user. Also the amount of useable CMOS ARM is pretty
> limited, even though the amount of CMOS bytes emulated by qemu is
> already twice as much as of the original MC146818. Nevertheless those
> limitations are pretty annoying when testing different BIOS replacement
> implementations like coreboot in combination with FILO that use CMOS
> values above the basic RTC range for its own purpose to, e.g., control
> the boot device order using a string containing the boot devices to
> probe.
>
> This patch adds support to specify a file to read the initial CMOS
> content from. It also increases the CMOS size to 256 bytes and
> implements access to the extended memory range via I/O ports 0x72 and
> 0x73.
>
> Use it like: `qemu -global mc146818rtc.file=cmos.bin ...' where cmos.bin
> is a binary file, sized 256 bytes containing the CMOS RAM.
>
> Signed-off-by: Mathias Krause<address@hidden>
>    

Instead of using FILE, I'd suggest using a BlockDriver to read and write 
the data.

I think it would be very nice to add write support too so that writes to 
CMOS were persisted across boots.

> ---
>   hw/mc146818rtc.c |   62 ++++++++++++++++++++++++++++++++++++++++++++++++-----
>   1 files changed, 56 insertions(+), 6 deletions(-)
>
> diff --git a/hw/mc146818rtc.c b/hw/mc146818rtc.c
> index 2b91fa8..9f215e0 100644
> --- a/hw/mc146818rtc.c
> +++ b/hw/mc146818rtc.c
> @@ -78,12 +78,16 @@
>   #define REG_C_PF   0x40
>   #define REG_C_AF   0x20
>
> +#define BASE_PORT  0x70
> +#define CMOS_SIZE  256
> +
>   typedef struct RTCState {
>       ISADevice dev;
> -    uint8_t cmos_data[128];
> +    uint8_t cmos_data[CMOS_SIZE];
>       uint8_t cmos_index;
>       struct tm current_tm;
>       int32_t base_year;
> +    char *file;
>       qemu_irq irq;
>       qemu_irq sqw_irq;
>       int it_shift;
> @@ -206,7 +210,7 @@ static void cmos_ioport_write(void *opaque, uint32_t addr, 
> uint32_t data)
>       RTCState *s = opaque;
>
>       if ((addr&  1) == 0) {
> -        s->cmos_index = data&  0x7f;
> +        s->cmos_index = data&  (addr == BASE_PORT ? 0x7f : 0xff);
>       } else {
>           CMOS_DPRINTF("cmos: write index=0x%02x val=0x%02x\n",
>                        s->cmos_index, data);
> @@ -581,7 +585,6 @@ static void rtc_reset(void *opaque)
>   static int rtc_initfn(ISADevice *dev)
>   {
>       RTCState *s = DO_UPCAST(RTCState, dev, dev);
> -    int base = 0x70;
>
>       s->cmos_data[RTC_REG_A] = 0x26;
>       s->cmos_data[RTC_REG_B] = 0x02;
> @@ -603,14 +606,57 @@ static int rtc_initfn(ISADevice *dev)
>           qemu_get_clock(rtc_clock) + (get_ticks_per_sec() * 99) / 100;
>       qemu_mod_timer(s->second_timer2, s->next_second_time);
>
> -    register_ioport_write(base, 2, 1, cmos_ioport_write, s);
> -    register_ioport_read(base, 2, 1, cmos_ioport_read, s);
> +    register_ioport_write(BASE_PORT, 4, 1, cmos_ioport_write, s);
> +    register_ioport_read(BASE_PORT, 4, 1, cmos_ioport_read, s);
>
> -    qdev_set_legacy_instance_id(&dev->qdev, base, 2);
> +    qdev_set_legacy_instance_id(&dev->qdev, BASE_PORT, 2);
>       qemu_register_reset(rtc_reset, s);
>       return 0;
>   }
>
> +static long get_file_size(FILE *f)
> +{
> +    long where, size;
> +
> +    /* XXX: on Unix systems, using fstat() probably makes more sense */
> +
> +    where = ftell(f);
> +    fseek(f, 0, SEEK_END);
> +    size = ftell(f);
> +    fseek(f, where, SEEK_SET);
> +
> +    return size;
> +}
>    

BlockDrivers have a getlength() functions.

Regards,

Anthony Liguori