Re: [PATCH RFC] usb: typec: thunderbolt: Fix Thunderbolt adapter type bitfield values

Heikki Krogerus
2025-10-08T10:41:41Z

On Fri, Sep 26, 2025 at 02:32:57PM +0200, Konrad Dybcio wrote:
> From: Konrad Dybcio <konrad.dybcio@oss.qualcomm.com>
>
> The value has been amended with the release of the USB Type-C
> Specification v2.1, reportedly as an erratum.
>
> Signed-off-by: Konrad Dybcio <konrad.dybcio@oss.qualcomm.com>

Makes sense to me. FWIW:

Reviewed-by: Heikki Krogerus <heikki.krogerus@linux.intel.com>

> ---
> I bundled a change to the CrOS EC driver based on the assumption that
> it worked around the faulty definition. I see the Intel PMC mux driver
> also checks for this bit, but it seems like that driver assumes that
> the value is in-spec (i.e. it may be buggy as of right now).
>
> Adding the respective maintainers to make sure everyone can see this.
> ---
> drivers/platform/chrome/cros_ec_typec.c | 2 +-
> include/linux/usb/typec_tbt.h | 4 ++--
> 2 files changed, 3 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/platform/chrome/cros_ec_typec.c b/drivers/platform/chrome/cros_ec_typec.c
> index b712bcff6fb2674ec79286159090df6d79b32e9a..d80f3de1b87c362a2825bd19f826c5be077583aa 100644
> --- a/drivers/platform/chrome/cros_ec_typec.c
> +++ b/drivers/platform/chrome/cros_ec_typec.c
> @@ -585,7 +585,7 @@ static int cros_typec_enable_tbt(struct cros_typec_data *typec,
> data.device_mode = TBT_MODE;
>
> if (pd_ctrl->control_flags & USB_PD_CTRL_TBT_LEGACY_ADAPTER)
> - data.device_mode = TBT_SET_ADAPTER(TBT_ADAPTER_TBT3);
> + data.device_mode = TBT_SET_ADAPTER(TBT_ADAPTER_LEGACY);
>
> /* Cable Discover Mode VDO */
> data.cable_mode = TBT_MODE;
> diff --git a/include/linux/usb/typec_tbt.h b/include/linux/usb/typec_tbt.h
> index 55dcea12082c80defeb6f199ad333279b58adcd7..6bf208c9dd5037f162678bc0be5be7ae1ca0deca 100644
> --- a/include/linux/usb/typec_tbt.h
> +++ b/include/linux/usb/typec_tbt.h
> @@ -27,8 +27,8 @@ struct typec_thunderbolt_data {
> /* TBT3 Device Discover Mode VDO bits */
> #define TBT_MODE BIT(0)
> #define TBT_ADAPTER(_vdo_) FIELD_GET(BIT(16), _vdo_)
> -#define TBT_ADAPTER_LEGACY 0
> -#define TBT_ADAPTER_TBT3 1
> +#define TBT_ADAPTER_TBT3 0
> +#define TBT_ADAPTER_LEGACY 1
> #define TBT_INTEL_SPECIFIC_B0 BIT(26)
> #define TBT_VENDOR_SPECIFIC_B0 BIT(30)
> #define TBT_VENDOR_SPECIFIC_B1 BIT(31)
>
> ---
> base-commit: 8e2755d7779a95dd61d8997ebce33ff8b1efd3fb
> change-id: 20250926-topic-tbt_header_bit_fix-17aeb524df4a
>
> Best regards,
> --
> Konrad Dybcio <konrad.dybcio@oss.qualcomm.com>

--
heikki