Re: [PATCH 1/7] hw/i2c: pmbus add support for block receive

[Corey Minyard <minyard@acm.org>]

On Fri, Mar 31, 2023 at 12:07:50AM +0000, Titus Rwantare wrote:
> PMBus devices can send and receive variable length data using the
> block read and write format, with the first byte in the payload
> denoting the length.
> 
> This is mostly used for strings and on-device logs. Devices can
> respond to a block read with an empty string.
> 
> Reviewed-by: Hao Wu <wuhaotsh@google.com>
> Signed-off-by: Titus Rwantare <titusr@google.com>

Acked-by: Corey Minyard <cminyard@mvista.com>

> ---
>  hw/i2c/pmbus_device.c         | 30 +++++++++++++++++++++++++++++-
>  include/hw/i2c/pmbus_device.h |  7 +++++++
>  2 files changed, 36 insertions(+), 1 deletion(-)
> 
> diff --git a/hw/i2c/pmbus_device.c b/hw/i2c/pmbus_device.c
> index c3d6046784..02647769cd 100644
> --- a/hw/i2c/pmbus_device.c
> +++ b/hw/i2c/pmbus_device.c
> @@ -95,7 +95,6 @@ void pmbus_send64(PMBusDevice *pmdev, uint64_t data)
>  void pmbus_send_string(PMBusDevice *pmdev, const char *data)
>  {
>      size_t len = strlen(data);
> -    g_assert(len > 0);
>      g_assert(len + pmdev->out_buf_len < SMBUS_DATA_MAX_LEN);
>      pmdev->out_buf[len + pmdev->out_buf_len] = len;
>  
> @@ -105,6 +104,35 @@ void pmbus_send_string(PMBusDevice *pmdev, const char *data)
>      pmdev->out_buf_len += len + 1;
>  }
>  
> +uint8_t pmbus_receive_block(PMBusDevice *pmdev, uint8_t *dest, size_t len)
> +{
> +    /* dest may contain data from previous writes */
> +    memset(dest, 0, len);
> +
> +    /* Exclude command code from return value */
> +    pmdev->in_buf++;
> +    pmdev->in_buf_len--;
> +
> +    /* The byte after the command code denotes the length */
> +    uint8_t sent_len = pmdev->in_buf[0];
> +
> +    if (sent_len != pmdev->in_buf_len - 1) {
> +        qemu_log_mask(LOG_GUEST_ERROR,
> +                      "%s: length mismatch. Expected %d bytes, got %d bytes\n",
> +                      __func__, sent_len, pmdev->in_buf_len - 1);
> +    }
> +
> +    /* exclude length byte */
> +    pmdev->in_buf++;
> +    pmdev->in_buf_len--;
> +
> +    if (pmdev->in_buf_len < len) {
> +        len = pmdev->in_buf_len;
> +    }
> +    memcpy(dest, pmdev->in_buf, len);
> +    return len;
> +}
> +
>  
>  static uint64_t pmbus_receive_uint(PMBusDevice *pmdev)
>  {
> diff --git a/include/hw/i2c/pmbus_device.h b/include/hw/i2c/pmbus_device.h
> index 93f5d57c9d..7dc00cc4d9 100644
> --- a/include/hw/i2c/pmbus_device.h
> +++ b/include/hw/i2c/pmbus_device.h
> @@ -501,6 +501,13 @@ void pmbus_send64(PMBusDevice *state, uint64_t data);
>   */
>  void pmbus_send_string(PMBusDevice *state, const char *data);
>  
> +/**
> + * @brief Receive data sent with Block Write.
> + * @param dest - memory with enough capacity to receive the write
> + * @param len - the capacity of dest
> + */
> +uint8_t pmbus_receive_block(PMBusDevice *pmdev, uint8_t *dest, size_t len);
> +
>  /**
>   * @brief Receive data over PMBus
>   * These methods help track how much data is being received over PMBus
> -- 
> 2.40.0.423.gd6c402a77b-goog
>