Re: [PATCH v6 1/3] hw/i2c: add smbus pec utility function

[Andrew Jeffery <andrew@codeconstruct.com.au>]

On Thu, 2023-09-14 at 11:53 +0200, Klaus Jensen wrote:
> From: Klaus Jensen <k.jensen@samsung.com>
> 
> Add i2c_smbus_pec() to calculate the SMBus Packet Error Code for a
> message.
> 
> Reviewed-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
> Signed-off-by: Klaus Jensen <k.jensen@samsung.com>

It at least looks a lot like the linux implementation :)

Reviewed-by: Andrew Jeffery <andrew@codeconstruct.com.au>

> ---
>  hw/i2c/smbus_master.c         | 26 ++++++++++++++++++++++++++
>  include/hw/i2c/smbus_master.h |  2 ++
>  2 files changed, 28 insertions(+)
> 
> diff --git a/hw/i2c/smbus_master.c b/hw/i2c/smbus_master.c
> index 6a53c34e70b7..01a8e4700222 100644
> --- a/hw/i2c/smbus_master.c
> +++ b/hw/i2c/smbus_master.c
> @@ -15,6 +15,32 @@
>  #include "hw/i2c/i2c.h"
>  #include "hw/i2c/smbus_master.h"
>  
> +static uint8_t crc8(uint16_t data)
> +{
> +    int i;
> +
> +    for (i = 0; i < 8; i++) {
> +        if (data & 0x8000) {
> +            data ^= 0x1070U << 3;
> +        }
> +
> +        data <<= 1;
> +    }
> +
> +    return (uint8_t)(data >> 8);
> +}
> +
> +uint8_t i2c_smbus_pec(uint8_t crc, uint8_t *buf, size_t len)
> +{
> +    int i;
> +
> +    for (i = 0; i < len; i++) {
> +        crc = crc8((crc ^ buf[i]) << 8);
> +    }
> +
> +    return crc;
> +}
> +
>  /* Master device commands.  */
>  int smbus_quick_command(I2CBus *bus, uint8_t addr, int read)
>  {
> diff --git a/include/hw/i2c/smbus_master.h b/include/hw/i2c/smbus_master.h
> index bb13bc423c22..d90f81767d86 100644
> --- a/include/hw/i2c/smbus_master.h
> +++ b/include/hw/i2c/smbus_master.h
> @@ -27,6 +27,8 @@
>  
>  #include "hw/i2c/i2c.h"
>  
> +uint8_t i2c_smbus_pec(uint8_t crc, uint8_t *buf, size_t len);
> +
>  /* Master device commands.  */
>  int smbus_quick_command(I2CBus *bus, uint8_t addr, int read);
>  int smbus_receive_byte(I2CBus *bus, uint8_t addr);
>