Re: [PATCH v3 3/4] usb: typec: ucsi: Register SOP/SOP' Discover Identity Responses

[Prashant Malani <pmalani@chromium.org>]

On Thu, Feb 29, 2024 at 3:28 PM Jameson Thies <jthies@google.com> wrote:
> diff --git a/drivers/usb/typec/ucsi/ucsi.c b/drivers/usb/typec/ucsi/ucsi.c
> index 7c84687b5d1a3..4088422b33c74 100644
> --- a/drivers/usb/typec/ucsi/ucsi.c
> +++ b/drivers/usb/typec/ucsi/ucsi.c
> @@ -646,6 +646,121 @@ static int ucsi_get_src_pdos(struct ucsi_connector *con)
>         return ret;
>  }
>
> +static int ucsi_read_identity(struct ucsi_connector *con, u8 recipient,
> +                             struct usb_pd_identity *id)
> +{
> +       struct ucsi *ucsi = con->ucsi;
> +       struct ucsi_pd_message_disc_id resp = {};
> +       u64 command;
> +       int ret;
> +
> +       if (ucsi->version < UCSI_VERSION_2_0) {
> +               /*
> +                * Before UCSI v2.0, MESSAGE_IN is 16 bytes which cannot fit
> +                * the 28 byte identity response including the VDM header.
> +                * First request the VDM header, ID Header VDO, Cert Stat VDO
> +                * and Product VDO.
> +                */
> +               command = UCSI_COMMAND(UCSI_GET_PD_MESSAGE) |
> +                   UCSI_CONNECTOR_NUMBER(con->num);
> +               command |= UCSI_GET_PD_MESSAGE_RECIPIENT(recipient);
> +               command |= UCSI_GET_PD_MESSAGE_OFFSET(0);
> +               command |= UCSI_GET_PD_MESSAGE_BYTES(0x10);
> +               command |= UCSI_GET_PD_MESSAGE_TYPE(
> +                   UCSI_GET_PD_MESSAGE_TYPE_IDENTITY);
> +
> +               ret = ucsi_send_command(ucsi, command, &resp, 0x10);
> +               if (ret < 0) {
> +                       dev_err(ucsi->dev,
> +                               "UCSI_GET_PD_MESSAGE v1.2 failed first request (%d)\n",
> +                               ret);
> +                       return ret;
> +               }
> +
> +               /* Then request Product Type VDO1 through Product Type VDO3. */
> +               command = UCSI_COMMAND(UCSI_GET_PD_MESSAGE) |
> +                   UCSI_CONNECTOR_NUMBER(con->num);
> +               command |= UCSI_GET_PD_MESSAGE_RECIPIENT(recipient);
> +               command |= UCSI_GET_PD_MESSAGE_OFFSET(0x10);
> +               command |= UCSI_GET_PD_MESSAGE_BYTES(0xc);
> +               command |= UCSI_GET_PD_MESSAGE_TYPE(
> +                   UCSI_GET_PD_MESSAGE_TYPE_IDENTITY);
> +
> +               ret = ucsi_send_command(ucsi, command, &resp.vdo[0], 0xc);
> +               if (ret < 0) {
> +                       dev_err(ucsi->dev,
> +                               "UCSI_GET_PD_MESSAGE v1.2 failed second request (%d)\n",
> +                               ret);
> +                       return ret;
> +               }
> +       } else {
> +               /*
> +                * In UCSI v2.0 and after, MESSAGE_IN is large enough to request
> +                * the large enough to request the full Discover Identity
> +                * response at once.
> +                */
> +               command = UCSI_COMMAND(UCSI_GET_PD_MESSAGE) |
> +                   UCSI_CONNECTOR_NUMBER(con->num);
> +               command |= UCSI_GET_PD_MESSAGE_RECIPIENT(recipient);
> +               /* VDM Header + 6 VDOs (0x1c bytes) without an offset */
> +               command |= UCSI_GET_PD_MESSAGE_OFFSET(0);
> +               command |= UCSI_GET_PD_MESSAGE_BYTES(0x1c);
> +               command |= UCSI_GET_PD_MESSAGE_TYPE(
> +                   UCSI_GET_PD_MESSAGE_TYPE_IDENTITY);
> +
> +               ret = ucsi_send_command(ucsi, command, &resp, sizeof(resp));
> +               if (ret < 0) {
> +                       dev_err(ucsi->dev, "UCSI_GET_PD_MESSAGE failed (%d)\n",
> +                               ret);
> +                       return ret;
> +               }
> +       }
> +
> +       id->id_header = resp.id_header;
> +       id->cert_stat = resp.cert_stat;
> +       id->product = resp.product;
> +       id->vdo[0] = resp.vdo[0];
> +       id->vdo[1] = resp.vdo[1];
> +       id->vdo[2] = resp.vdo[2];
> +       return 0;
> +}

There is some repetition here, both with the "if" block and the
UCSI command itself. You can factor out the command setup code into a separate
function (it can take offset and size as arguments). Then, factor out
common parts in the "if" block. For example:

int ucsi_pd_message_get_identity(struct *ucsi, u8 offset, u8 size, u8 recipient,
                                                              void *data) {
        u64 command = UCSI_COMMAND(UCSI_GET_PD_MESSAGE) |
UCSI_CONNECTOR_NUMBER(ucsi->con->num) |
                      UCSI_GET_PD_MESSAGE_RECIPIENT(recipient) |
                      UCSI_GET_PD_MESSAGE_OFFSET(offset) |
UCSI_GET_PD_MESSAGE_BYTES(size) |

UCSI_GET_PD_MESSAGE_TYPE(UCSI_GET_PD_MESSAGE_TYPE_IDENTITY);

        return ucsi_send_command(ucsi, command, data, size);
}

Then in the ucsi_read_identity() :
        u8 offset = 0;
        u8 size;

        /*
         * In UCSI v2.0 and after, MESSAGE_IN is large enough to request
         * the large enough to request the full Discover Identity
         * response at once.
         */
        if (ucsi->version >= UCSI_VERSION_2_0) {
                size = 0x1c;
        else
                size = 0x10;

        ret = ucsi_pd_message_get_identity(ucsi, offset, size, &resp);
        if (ret < 0) {
                /* Handle error */
        }

        /* Request Product Type VDO1 through Product Type VDO3. */
        if (ucsi->version < UCSI_VERSION_2_0) {
                offset = 0x10;
                size = 0xC;
                ret = ucsi_pd_message_get_identity(ucsi, offset, size,
&resp.vdo[0]);
                if (ret < 0) {
                /* Handle error */
                }
        }

BR,

-Prashant