Re: [Qemu-devel] [PATCH v3 14/16] i2c:smbus_eeprom: Add vmstate handling to the smbus eeprom

[Corey Minyard]

On 11/29/18 7:29 AM, Dr. David Alan Gilbert wrote:
> * address@hidden (address@hidden) wrote:
> > From: Corey Minyard <address@hidden>
> >
> > Transfer the state of the EEPROM on a migration.  This way the
> > data remains consistent on migration.
> >
> > This required moving the actual data to a separate array and
> > using the data provided in the init function as a separate
> > initialization array, since a pointer property has to be a
> > void * and the array needs to be uint8_t[].
> So I think I'm OK with this, but I'd like other peoples comments as
> well; see comments.


Well, no comments so far.

I have a question on this.  If this particular device were modified to 
be able
to support different size eeproms, would this need a new version of the
vmstate structure?  I know the vmstate structure itself would have to
change to have an array size, but would it have to change in such a
way that the array size would need to be transmitted?

I ask because someday, someone might need an eeprom of a different
size, and it would be nice if it could be done now in a way that avoided
creating a new version.

Thanks,

-corey

> > Signed-off-by: Corey Minyard <address@hidden>
> > Cc: Paolo Bonzini <address@hidden>
> > Cc: Michael S. Tsirkin <address@hidden>
> > Cc: Dr. David Alan Gilbert <address@hidden>
> > Cc: Peter Maydell <address@hidden>
> > ---
> >   hw/i2c/smbus_eeprom.c | 34 ++++++++++++++++++++++++++++++++--
> >   1 file changed, 32 insertions(+), 2 deletions(-)
> >
> > diff --git a/hw/i2c/smbus_eeprom.c b/hw/i2c/smbus_eeprom.c
> > index 8e9b734c09..942057dc10 100644
> > --- a/hw/i2c/smbus_eeprom.c
> > +++ b/hw/i2c/smbus_eeprom.c
> > @@ -24,6 +24,7 @@
> >   
> >   #include "qemu/osdep.h"
> >   #include "hw/hw.h"
> > +#include "hw/boards.h"
> >   #include "hw/i2c/i2c.h"
> >   #include "hw/i2c/smbus_slave.h"
> >   #include "hw/i2c/smbus_eeprom.h"
> > @@ -39,8 +40,10 @@
> >   
> >   typedef struct SMBusEEPROMDevice {
> >       SMBusDevice smbusdev;
> > -    void *data;
> > +    uint8_t data[SMBUS_EEPROM_SIZE];
> > +    void *init_data;
> >       uint8_t offset;
> > +    bool accessed;
> >   } SMBusEEPROMDevice;
> >   
> >   static uint8_t eeprom_receive_byte(SMBusDevice *dev)
> > @@ -49,6 +52,7 @@ static uint8_t eeprom_receive_byte(SMBusDevice *dev)
> >       uint8_t *data = eeprom->data;
> >       uint8_t val = data[eeprom->offset++];
> >   
> > +    eeprom->accessed = true;
> >   #ifdef DEBUG
> >       printf("eeprom_receive_byte: addr=0x%02x val=0x%02x\n",
> >              dev->i2c.address, val);
> > @@ -61,6 +65,7 @@ static int eeprom_write_data(SMBusDevice *dev, uint8_t *buf, 
> > uint8_t len)
> >       SMBusEEPROMDevice *eeprom = SMBUS_EEPROM(dev);
> >       uint8_t *data = eeprom->data;
> >   
> > +    eeprom->accessed = true;
> >   #ifdef DEBUG
> >       printf("eeprom_write_byte: addr=0x%02x cmd=0x%02x val=0x%02x\n",
> >              dev->i2c.address, cmd, buf[0]);
> > @@ -78,15 +83,39 @@ static int eeprom_write_data(SMBusDevice *dev, uint8_t 
> > *buf, uint8_t len)
> >       return 0;
> >   }
> >   
> > +static bool smbus_eeprom_vmstate_needed(void *opaque)
> > +{
> > +    MachineClass *mc = MACHINE_GET_CLASS(qdev_get_machine());
> > +    SMBusEEPROMDevice *eeprom = opaque;
> > +
> > +    return (eeprom->accessed || smbus_vmstate_needed(&eeprom->smbusdev)) &&
> > +        !mc->smbus_no_migration_support;
> That's a little complx, but OK.
>
> > +}
> > +
> > +static const VMStateDescription vmstate_smbus_eeprom = {
> > +    .name = "smbus-eeprom",
> > +    .version_id = 1,
> > +    .minimum_version_id = 1,
> > +    .needed = smbus_eeprom_vmstate_needed,
> > +    .fields      = (VMStateField[]) {
> > +        VMSTATE_SMBUS_DEVICE(smbusdev, SMBusEEPROMDevice),
> > +        VMSTATE_UINT8_ARRAY(data, SMBusEEPROMDevice, SMBUS_EEPROM_SIZE),
> > +        VMSTATE_UINT8(offset, SMBusEEPROMDevice),
> > +        VMSTATE_BOOL(accessed, SMBusEEPROMDevice),
> OK, good - including 'accessed' means that if we migrate a->b->c and
> it's not changed while it's on b, then 'c' still gets the updated
> version.
>
> > +        VMSTATE_END_OF_LIST()
> > +    }
> > +};
> > +
> >   static void smbus_eeprom_realize(DeviceState *dev, Error **errp)
> >   {
> >       SMBusEEPROMDevice *eeprom = SMBUS_EEPROM(dev);
> >   
> > +    memcpy(eeprom->data, eeprom->init_data, SMBUS_EEPROM_SIZE);
> >       eeprom->offset = 0;
> >   }
> >   
> >   static Property smbus_eeprom_properties[] = {
> > -    DEFINE_PROP_PTR("data", SMBusEEPROMDevice, data),
> > +    DEFINE_PROP_PTR("data", SMBusEEPROMDevice, init_data),
> >       DEFINE_PROP_END_OF_LIST(),
> >   };
> >   
> > @@ -99,6 +128,7 @@ static void smbus_eeprom_class_initfn(ObjectClass *klass, void *data)
> >       sc->receive_byte = eeprom_receive_byte;
> >       sc->write_data = eeprom_write_data;
> >       dc->props = smbus_eeprom_properties;
> > +    dc->vmsd = &vmstate_smbus_eeprom;
> >       /* Reason: pointer property "data" */
> >       dc->user_creatable = false;
> >   }
> so from migration side:
>
>
> Reviewed-by: Dr. David Alan Gilbert <address@hidden>
>
> > --
> > 2.17.1
> --
> Dr. David Alan Gilbert / address@hidden / Manchester, UK