From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from out-186.mta0.migadu.com (out-186.mta0.migadu.com [91.218.175.186]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 9F8322E1F06; Tue, 21 Jul 2026 16:01:36 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=91.218.175.186 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1784649698; cv=none; b=aYZ3V9jtVwmjkai0mdPIuMrLgz5NLmwE4GQMhHAkyGkaJkRWa2vYHc7YYBS9PIQSwQ6iCw6ClkFU4EBsxBwRKN5mc+zpWJnOYNhSByp8kAW+f394/U9WapPBqH5MDsw1CjexRsyRdQ/jGahoafY2ufDEezwWVIU/ZXdVzZ4YKF4= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1784649698; c=relaxed/simple; bh=HIlFykM+aU0w04oZ1TxF/xznHCRRKSbrYIfTc5+x6ng=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=RIK/wcAsENjIpwfnFjuL0vq++swXUqjx1f4UJLwsazKO8afwexrNRFWPoaeqSjAJ4ZufYrlxk4ltjWjDeoXlA+p0a5U6N0YKmZyajr1kCVDHG5w/G88fIRPf45NiYcNmhp5XnukYIL3uKHBsXnL5dTpQx7LyIjNa8jsDtCgfSk8= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev; spf=pass smtp.mailfrom=linux.dev; dkim=pass (1024-bit key) header.d=linux.dev header.i=@linux.dev header.b=ussrbNWz; arc=none smtp.client-ip=91.218.175.186 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linux.dev Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux.dev header.i=@linux.dev header.b="ussrbNWz" Date: Tue, 21 Jul 2026 18:01:10 +0200 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1784649694; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=eys/4Qe9QDzUBYysnEj0pqqrB6eil2IcXI5qwah6udo=; b=ussrbNWzBVn+GgvkioZvHj5ok85wxaUW1WsjIacELNqhDll7G7vMfzdxTDBGzzVdv8S4Xt n+UsYRXHnFPCovhbrxOtytp1TeW4w3gagd7xY4PYYg2vlWjMRqzF8k3cFPVlESgzV8pgLC HkJCIxOpoF1h0N/VOJmL+UpcIIRVqbw= X-Report-Abuse: Please report any abuse attempt to abuse@migadu.com and include these headers. From: Richard Leitner To: Laurent Pinchart Cc: Dave Stevenson , Mauro Carvalho Chehab , Sakari Ailus , Hans de Goede , linux-media@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH 2/2] media: ov9282: enable single-read I2C transactions Message-ID: References: <20260721-cci-single-v1-0-8485171e1393@linux.dev> <20260721-cci-single-v1-2-8485171e1393@linux.dev> <20260721151614.GN50424@killaraus.ideasonboard.com> <20260721155822.GB536385@killaraus.ideasonboard.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20260721155822.GB536385@killaraus.ideasonboard.com> X-Migadu-Flow: FLOW_OUT On Tue, Jul 21, 2026 at 06:58:22PM +0300, Laurent Pinchart wrote: > On Tue, Jul 21, 2026 at 05:44:21PM +0200, Richard Leitner wrote: > > Hi Laurent, > > > > thank you very much for your quick feedback! > > > > On Tue, Jul 21, 2026 at 06:16:14PM +0300, Laurent Pinchart wrote: > > > On Tue, Jul 21, 2026 at 02:39:46PM +0100, Dave Stevenson wrote: > > > > On Tue, 21 Jul 2026 at 14:25, Richard Leitner wrote: > > > > > > > > > > Some OV9282 camera modules, such as those from Vision Components, fail > > > > > multi-byte register reads with the default CCI I2C regmap access pattern > > > > > and only work when single-register read transactions are used. This > > > > > results in the driver being unable to probe due to a chip id mismatch. > > > > > > > > Those damn stupid Vision Components modules with the MCU that prevents > > > > you reading registers. > > > > > > There's good news, the situation is improving with recent modules. We > > > still have to handle the other ones of course. > > > > > > > I seem to recall Laurent had a plan for how to handle those without > > > > having to patch all the drivers, however I can't find that thread > > > > quickly. > > > > > > I'm thinking of two options: > > > > > > - We can introduce a new standard DT property for I2C device that will > > > be parsed by regmap or the I2C core directly, and switch to single > > > reads. > > > > > > - We could model the MCU as some sort of I2C mux, sitting in DT between > > > the I2C controller and the image sensor, and translate multi-byte > > > reads to single-byte reads in that driver. > > > > I'm basically fine with both. Personally I would prefer the first > > option, as this would be a generic approach which other devices could also > > use. Furthermore it's IMHO the simpler solution. But that's just my 2 cents. > > The next step is to then write and send an RFC, to get feedback on the > idea from the DT and I2C maintainers (and possibly regmap, if we handle > the quirk at that level). Is that something you could work on ? Sure. I'll take a more detailled look at it tomorrow. regards;rl ... > -- > Regards, > > Laurent Pinchart