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[150.31.20.132]) by smtp.gmail.com with ESMTPSA id 5a478bee46e88-36a42aa8999sm8144599eec.29.2026.10.30.05.12.37 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 30 Oct 2026 05:12:38 -0700 (PDT) From: Antoine Pichot To: linux-media@vger.kernel.org Cc: sakari.ailus@linux.intel.com, mchehab@kernel.org, hansg@kernel.org, andriy.shevchenko@linux.intel.com, dan.scally@ideasonboard.com, djrscally@gmail.com, dmanresa@gmail.com, dave.stevenson@raspberrypi.com, linux-kernel@vger.kernel.org Subject: Re: [PATCH v2 8/9] media: i2c: ov7251: Add strobe output enable control Date: Fri, 30 Oct 2026 21:12:35 +0900 Message-ID: <20261030121235.2163478-1-antoine.pichot@gmail.com> X-Mailer: git-send-email 2.56.0 In-Reply-To: <20261028112154.855185-9-antoine.pichot@gmail.com> References: <20261028112154.855185-1-antoine.pichot@gmail.com> <20261028112154.855185-9-antoine.pichot@gmail.com> X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Hi, On Tue, Oct 28, 2026, Antoine Pichot wrote: > Alternate frames is what the Windows driver uses for face recognition > on this hardware: its 30 and 60 fps modes write 0xaa, and a register > dump taken during a Windows Hello sign-in on a Surface Book 2 shows the > same. Lighting every frame (0xff, which two of its other modes use) > would double the average emitter power. User space tells lit frames > from dark ones by their brightness; V4L2 has no per-frame illumination > flag yet. Before I send v3, could you please say which of these two you prefer? V4L2_CID_FLASH_STROBE_OE is a boolean: it turns the strobe pin on or off. Two sensor settings then shape the signal: how long the pulse lasts within a frame (the span, which this driver ties to the exposure), and which frames get a pulse at all (the pattern, one bit per frame over eight frames). V4L2 has no control for the pattern. ov9282 writes 0xff in its common register table, a pulse on every frame; this patch writes 0xaa, a pulse on alternate frames. Both chips default to 0xa5, four frames in eight, so a driver has to pick one. - when the control is on, pulse alternate frames, as in this patch; - when the control is on, pulse every frame, like ov9282, and add a menu control "Strobe Frame Pattern" with "Every frame" and "Alternate frames", after the infrared torch mode of the Windows camera API (off, always on, alternating frame illumination). Either way the pattern is one register write. Thanks, Antoine