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Manresa" , Jizhou Tong , linux-media@vger.kernel.org, devicetree@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v3 2/4] media: i2c: Add ST VD55G0 global shutter sensor driver Message-ID: <20261110194620.46374-1-lsa.uz@pm.me> In-Reply-To: <3750472c-5a49-48f6-a8bf-0bae45e4c01b@foss.st.com> References: <20261109093353.3757-1-lsa.uz@pm.me> <20261109093353.3757-3-lsa.uz@pm.me> <20261109124610.85065-1-lsa.uz@pm.me> <20261109132746.22125-1-lsa.uz@pm.me> <3750472c-5a49-48f6-a8bf-0bae45e4c01b@foss.st.com> Feedback-ID: 113843758:user:proton X-Pm-Message-ID: a6624b0f434eaf29d2bdf4eea112c843ac323dd3 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-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable Hi Benjamin, On Tue, Nov 10, 2026 at 10:46:57AM +0100, Benjamin Mugnier wrote: > From a user perspective they are mostly interchangeable. vd55g1 uses > AE_TARGET_PERCENTAGE while vd56g3 uses AE_COMPENSATION for instance. > > The downstream driver uses AE_TARGET_PERCENTAGE and that's why you have > it here. It would make more sense to use AE_COMPENSATION semantic wise, > but this is not a deal breaker. I tried AE_COMPENSATION on the VD55G0 here, with the firmware patch the driver loads. Positive values work as UM2829 says, but a negative one drives the AE to its maximum. A white sheet in front of the camera, the illuminator on, each value in a stream of its own: - AE_TARGET_PERCENTAGE 7, 14, 27: exposure 27, 49, 89 lines; - target 7 with +1 EV (0x0100) and +2 EV (0x0200): 48 and 91 lines; - target 14 with -1 EV (0xff00): 1796 lines, analogue gain 24, digital gain 2048. On the Dgrey test pattern every negative value did the same: -0.5, -1 and -2 EV in two's complement, and -1 and -2 EV as sign and magnitude (0x8100, 0x8200). AE_TARGET_PERCENTAGE works both ways, so v4 keeps it. Is this known for the VD55G0 firmware? Sergey