On 7/16/26 4:50 PM, Maxime Ripard wrote:
> On Wed, Jul 15, 2026 at 01:46:12PM +0300, Cristian Ciocaltea wrote:
>> On 7/15/26 11:55 AM, Maxime Ripard wrote:
>>> On Mon, Jul 13, 2026 at 01:23:00PM +0300, Cristian Ciocaltea wrote:
>>>> On 7/13/26 11:50 AM, Maxime Ripard wrote:
>>>>> On Thu, Jul 09, 2026 at 10:25:54PM +0300, Cristian Ciocaltea wrote:
>>>>>> On 7/3/26 11:54 PM, Cristian Ciocaltea wrote:
>>>>>>> On 7/3/26 5:34 PM, Dmitry Baryshkov wrote:
>>>>>>>> On Thu, Jul 02, 2026 at 05:46:17PM +0300, Cristian Ciocaltea wrote:
>>>>>>>>> Add the connector-level infrastructure to support HDMI 2.0 scrambling:
>>>>>>>>>
>>>>>>>>> - A scrambler_supported flag to indicate whether the source supports
>>>>>>>>> the
>>>>>>>>> scrambling capability, in which case the newly introduced
>>>>>>>>> .scrambler_{enable|disable}() callbacks in drm_connector_hdmi_funcs
>>>>>>>>> are mandatory
>>>>>>>>
>>>>>>>> Do we need a flag? What would it mean if the flag is set, but the
>>>>>>>> callbacks are not? Can we drop the flag and use the presence of the
>>>>>>>> callbacks as a way to identify that scrambler is enabled?
>>>>>>>
>>>>>>> The flag is intended to be set only within
>>>>>>> drmm_connector_hdmi_init_with_caps()
>>>>>>> when drivers advertise HDMI 2.x capability, in which case it also
>>>>>>> ensures the
>>>>>>> callbacks are provided.
>>>>>>>
>>>>>>> We could drop the flag and instead have the init helper clear the
>>>>>>> callbacks if
>>>>>>> they were provided for HDMI 1.x. This might slightly reduce code
>>>>>>> readability,
>>>>>>> as it relies on checking the presence of individual callbacks -
>>>>>>> especially since
>>>>>>> we plan to extend this further with HDMI 2.1 support, providing four or
>>>>>>> five
>>>>>>> additional FRL-specific callbacks.
>>>>>>
>>>>>> I tried to replace the flag with a helper that checks the presence of
>>>>>> (one of)
>>>>>> the callbacks, but it's not straightforward to unset those for non-HDMI
>>>>>> 2.x
>>>>>> cases since the hdmi_funcs argument is immutable.
>>>>>
>>>>> I'm not sure why we would need to unset them. If the driver states that
>>>>> it support HDMI 2.0, then it needs to be there, if it doesn't, then who
>>>>> cares? it's not going to be used. We can log a warning that it's
>>>>> inconsistent I guess, but there's no need to actively remove it.
>>>>
>>>> I was trying to address the use case where drivers provide the scrambler
>>>> callbacks despite not supporting HDMI 2.0.
>>>
>>> Scrambling got introduced with HDMI 2.0. That doesn't make sense, but
>>> it's not a total deal breaker, it's just going to be here unused. Hence
>>> why I was suggesting to put a warning there if you wanted to.
>>>
>>>> If we replace the scrambler_supported flag with a helper checking the
>>>> presence of the scrambler callbacks, then we would need to ensure the
>>>> callbacks do not exist in this case.
>>>
>>> Keep it simple:
>>>
>>> if (hdmi_version >= HDMI_VERSION_2_0)
>>> if (funcs->scrambler_enable)
>>> hdmi->scramblers_supported = true
>>> else
>>> return -EINVAL
>>> else
>>> drm_warn(warn, "Inconsistent HDMI version");
>>>
>>> We don't need anything more than that.
>>
>> I dropped the scrambler_supported flag and introduced a helper:
>>
>> static inline bool
>> drm_connector_hdmi_scrambler_supported(struct drm_connector *connector)
>> {
>> return connector->hdmi.funcs && connector->hdmi.funcs->scrambler_enable;
>
> I'd add disable to that test
If scrambler_enable is present, scrambler_disable is also present, as guaranteed
by the init validation below. I assume you'd like to have it added regardless,
to improve code readability, which is a fair point.
>> }
>>
>> Therefore we need to ensure the callbacks are not set in the HDMI 1.x cases:
>>
>> int drmm_connector_hdmi_init_with_caps()
>> {
>> ...
>> if (caps->supported_hdmi_ver >= HDMI_VERSION_2_0) {
>> if (!hdmi_funcs->scrambler_enable ||
>> !hdmi_funcs->scrambler_disable)
>> return -EINVAL;
>>
>> connector->hdmi.max_tmds_char_rate =
>> HDMI_2_0_TMDS_CHAR_RATE_MAX_HZ;
>> } else {
>> /*
>> * Scrambler callbacks are only valid for connectors advertising
>> * HDMI 2.0 capability. drm_connector_hdmi_scrambler_supported()
>> * relies on their presence to report scrambling support.
>> */
>> if (hdmi_funcs->scrambler_enable ||
>> hdmi_funcs->scrambler_disable)
>> return -EINVAL;
>>
>> if (caps->supported_hdmi_ver >= HDMI_VERSION_1_3) {
>> connector->hdmi.max_tmds_char_rate =
>> HDMI_1_3_TMDS_CHAR_RATE_MAX_HZ;
>> } else if (caps->supported_hdmi_ver >= HDMI_VERSION_1_0) {
>> connector->hdmi.max_tmds_char_rate =
>> HDMI_1_0_TMDS_CHAR_RATE_MAX_HZ;
>> }
>> }
>
> Drivers might have a lower limit than the max allowed by the spec. It
> should be provided by the driver, possibly optionally with a fallback to
> what the spec states?
Yes, this has been already part of patch 2 (also added an error message to help
with debugging):
if (caps->max_tmds_char_rate) {
if (caps->max_tmds_char_rate >
connector->hdmi.max_tmds_char_rate) {
drm_err(dev, "Enforced max_tmds_char_rate exceeds %llu
spec limit\n",
connector->hdmi.max_tmds_char_rate);
return -EINVAL;
}
connector->hdmi.max_tmds_char_rate = caps->max_tmds_char_rate;
}
Regards,
Cristian
