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 <wuhao...@google.com>
> Signed-off-by: Titus Rwantare <tit...@google.com>
Acked-by: Corey Minyard <cminy...@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
>
