Re: [PATCH v3 3/5] hw/nvram/eeprom_at24c: Add init_rom field and at24c_eeprom_init_rom helper

[Joel Stanley]

On Tue, 17 Jan 2023 at 23:24, Peter Delevoryas <peter@pjd.dev> wrote:
>
> Allows users to specify binary data to initialize an EEPROM, allowing users to
> emulate data programmed at manufacturing time.

I like it. Is there somewhere sensible to add a description to the
code base? Perhaps as a comment to your new function?

>
> - Added init_rom and init_rom_size attributes to TYPE_AT24C_EE
> - Added at24c_eeprom_init_rom helper function to initialize attributes
> - If -drive property is provided, it overrides init_rom data
>
> Signed-off-by: Peter Delevoryas <peter@pjd.dev>

Reviewed-by: Joel Stanley <joel@jms.id.au>

> ---
>  hw/nvram/eeprom_at24c.c         | 37 ++++++++++++++++++++++++++++-----
>  include/hw/nvram/eeprom_at24c.h |  2 ++
>  2 files changed, 34 insertions(+), 5 deletions(-)
>
> diff --git a/hw/nvram/eeprom_at24c.c b/hw/nvram/eeprom_at24c.c
> index 98857e3626b9..f8d751fa278d 100644
> --- a/hw/nvram/eeprom_at24c.c
> +++ b/hw/nvram/eeprom_at24c.c
> @@ -50,6 +50,9 @@ struct EEPROMState {
>      uint8_t *mem;
>
>      BlockBackend *blk;
> +
> +    const uint8_t *init_rom;
> +    uint32_t init_rom_size;
>  };
>
>  static
> @@ -131,19 +134,38 @@ int at24c_eeprom_send(I2CSlave *s, uint8_t data)
>
>  I2CSlave *at24c_eeprom_init(I2CBus *bus, uint8_t address, uint32_t rom_size)
>  {
> -    I2CSlave *i2c_dev = i2c_slave_new(TYPE_AT24C_EE, address);
> -    DeviceState *dev = DEVICE(i2c_dev);
> +    return at24c_eeprom_init_rom(bus, address, rom_size, NULL, 0);
> +}
> +
> +I2CSlave *at24c_eeprom_init_rom(I2CBus *bus, uint8_t address, uint32_t 
> rom_size,
> +                                const uint8_t *init_rom, uint32_t 
> init_rom_size)
> +{
> +    EEPROMState *s;
> +
> +    s = AT24C_EE(qdev_new(TYPE_AT24C_EE));
> +
> +    qdev_prop_set_uint8(DEVICE(s), "address", address);
> +    qdev_prop_set_uint32(DEVICE(s), "rom-size", rom_size);
>
> -    qdev_prop_set_uint32(dev, "rom-size", rom_size);
> -    i2c_slave_realize_and_unref(i2c_dev, bus, &error_abort);
> +    /* TODO: Model init_rom with QOM properties. */
> +    s->init_rom = init_rom;
> +    s->init_rom_size = init_rom_size;
>
> -    return i2c_dev;
> +    i2c_slave_realize_and_unref(I2C_SLAVE(s), bus, &error_abort);
> +
> +    return I2C_SLAVE(s);
>  }
>
>  static void at24c_eeprom_realize(DeviceState *dev, Error **errp)
>  {
>      EEPROMState *ee = AT24C_EE(dev);
>
> +    if (ee->init_rom_size > ee->rsize) {
> +        error_setg(errp, "%s: init rom is larger than rom: %u > %u",
> +                   TYPE_AT24C_EE, ee->init_rom_size, ee->rsize);
> +        return;
> +    }
> +
>      if (ee->blk) {
>          int64_t len = blk_getlength(ee->blk);
>
> @@ -163,6 +185,7 @@ static void at24c_eeprom_realize(DeviceState *dev, Error 
> **errp)
>      }
>
>      ee->mem = g_malloc0(ee->rsize);
> +
>  }
>
>  static
> @@ -176,6 +199,10 @@ void at24c_eeprom_reset(DeviceState *state)
>
>      memset(ee->mem, 0, ee->rsize);
>
> +    if (ee->init_rom) {
> +        memcpy(ee->mem, ee->init_rom, MIN(ee->init_rom_size, ee->rsize));

I like the MIN here; good usability feature. It's worth documenting too.

> +    }
> +
>      if (ee->blk) {
>          int ret = blk_pread(ee->blk, 0, ee->rsize, ee->mem, 0);
>
> diff --git a/include/hw/nvram/eeprom_at24c.h b/include/hw/nvram/eeprom_at24c.h
> index 196db309d451..5c9149331144 100644
> --- a/include/hw/nvram/eeprom_at24c.h
> +++ b/include/hw/nvram/eeprom_at24c.h
> @@ -19,5 +19,7 @@
>   * @bus, and drop the reference to it (the device is realized).
>   */
>  I2CSlave *at24c_eeprom_init(I2CBus *bus, uint8_t address, uint32_t rom_size);
> +I2CSlave *at24c_eeprom_init_rom(I2CBus *bus, uint8_t address, uint32_t 
> rom_size,
> +                                const uint8_t *init_rom, uint32_t 
> init_rom_size);
>
>  #endif
> --
> 2.39.0
>