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Wed, 15 Jul 2026 12:46:13 +0200 (CEST) Message-ID: Date: Wed, 15 Jul 2026 13:46:12 +0300 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v8 04/39] drm/connector: Add HDMI 2.0 scrambler infrastructure To: Maxime Ripard Cc: Dmitry Baryshkov , Maarten Lankhorst , Thomas Zimmermann , David Airlie , Simona Vetter , Andrzej Hajda , Neil Armstrong , Robert Foss , Laurent Pinchart , Jonas Karlman , Jernej Skrabec , Luca Ceresoli , Sandy Huang , =?UTF-8?Q?Heiko_St=C3=BCbner?= , Andy Yan , Daniel Stone , Dave Stevenson , =?UTF-8?Q?Ma=C3=ADra_Canal?= , Raspberry Pi Kernel Maintenance , kernel@collabora.com, dri-devel@lists.freedesktop.org, linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-rockchip@lists.infradead.org References: <20260702-dw-hdmi-qp-scramb-v8-0-d79890d00b6a@collabora.com> <20260702-dw-hdmi-qp-scramb-v8-4-d79890d00b6a@collabora.com> <17753a1c-824a-4835-ac2d-8b2796bba1eb@collabora.com> <534b921c-638c-4fc3-b89e-5dfc1f269f96@collabora.com> <20260713-statuesque-nonchalant-seagull-b9c39d@houat> <91c3a825-3344-4ff5-8ea0-f8f057665b3f@collabora.com> <20260715-ancient-zealous-eagle-b13e94@houat> Content-Language: en-US From: Cristian Ciocaltea In-Reply-To: <20260715-ancient-zealous-eagle-b13e94@houat> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.9.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20260715_034617_930829_C2EAE674 X-CRM114-Status: GOOD ( 24.79 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org 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; } 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; } } ... }