From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from perceval.ideasonboard.com (perceval.ideasonboard.com [213.167.242.64]) (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 39E2C1114; Wed, 27 Nov 2024 08:34:57 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=213.167.242.64 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1732696499; cv=none; b=OxUE8TpoJIK6gKbZoYm6/UOWtfSwApdhi7qT39n2nZxG/bB13Y4Y0R2cGvLOQNzUesqY57jbGsqN8qrWqwleRejoOUk8s8Zg6PhUXAFlrs0LldEt8n/IQu1l2RPLxcAIZl8IEtGNuF9UmCaRWCkz8ZlpJ/lgESaCt64MpMLePMU= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1732696499; c=relaxed/simple; bh=Ze4jFSr20glq2KKoEzubGfLgmXPognZt9fc7rqvDDaE=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=XBq9WDon5MGo9zXqhTNRCBNhQpS1v2RztySelBZO+U6cgbAdvrjj26vn0cGAK8THvK16I4zt3uxrlp9+egY9cuf6/qQT3OFXjzybqUdzGSkwE55W3Oe629ga2ecZbX+9qlsyJUHLHiKH/aZyvmlTD5Vb8YMuEEwYU3qzE8IOk48= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=ideasonboard.com; spf=pass smtp.mailfrom=ideasonboard.com; dkim=pass (1024-bit key) header.d=ideasonboard.com header.i=@ideasonboard.com header.b=ePtpbDGd; arc=none smtp.client-ip=213.167.242.64 Authentication-Results: smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=ideasonboard.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=ideasonboard.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=ideasonboard.com header.i=@ideasonboard.com header.b="ePtpbDGd" Received: from pendragon.ideasonboard.com (81-175-209-231.bb.dnainternet.fi [81.175.209.231]) by perceval.ideasonboard.com (Postfix) with ESMTPSA id 4E3B978C; Wed, 27 Nov 2024 09:34:32 +0100 (CET) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=ideasonboard.com; s=mail; t=1732696472; bh=Ze4jFSr20glq2KKoEzubGfLgmXPognZt9fc7rqvDDaE=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=ePtpbDGd5oHd9r6b/JsfGFZvqas1LznKEs6X1vKa1qcmKnQLQp3TQD8JtXcGebyCh 6o3XIuysKyPIYxmn1GTLSr+fwiYw6RMEvsl3JQh0n40EmDScnr2L32RYx9VapGSepm w/Z67XwZhBCAhKVX2na5J+dCBSoNjBaGzEmRIy+o= Date: Wed, 27 Nov 2024 10:34:44 +0200 From: Laurent Pinchart To: Ricardo Ribalda Cc: Hans de Goede , Mauro Carvalho Chehab , linux-media@vger.kernel.org, linux-kernel@vger.kernel.org, Sakari Ailus , stable@vger.kernel.org Subject: Re: [PATCH v4 1/2] media: uvcvideo: Support partial control reads Message-ID: <20241127083444.GV5461@pendragon.ideasonboard.com> References: <20241120-uvc-readless-v4-0-4672dbef3d46@chromium.org> <20241120-uvc-readless-v4-1-4672dbef3d46@chromium.org> <20241126180616.GL5461@pendragon.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: On Tue, Nov 26, 2024 at 07:12:53PM +0100, Ricardo Ribalda wrote: > On Tue, 26 Nov 2024 at 19:06, Laurent Pinchart wrote: > > On Wed, Nov 20, 2024 at 03:26:19PM +0000, Ricardo Ribalda wrote: > > > Some cameras, like the ELMO MX-P3, do not return all the bytes > > > requested from a control if it can fit in less bytes. > > > Eg: Returning 0xab instead of 0x00ab. > > > usb 3-9: Failed to query (GET_DEF) UVC control 3 on unit 2: 1 (exp. 2). > > > > > > Extend the returned value from the camera and return it. > > > > > > Cc: stable@vger.kernel.org > > > Fixes: a763b9fb58be ("media: uvcvideo: Do not return positive errors in uvc_query_ctrl()") > > > Reviewed-by: Hans de Goede > > > Signed-off-by: Ricardo Ribalda > > > --- > > > drivers/media/usb/uvc/uvc_video.c | 16 ++++++++++++++++ > > > 1 file changed, 16 insertions(+) > > > > > > diff --git a/drivers/media/usb/uvc/uvc_video.c b/drivers/media/usb/uvc/uvc_video.c > > > index cd9c29532fb0..482c4ceceaac 100644 > > > --- a/drivers/media/usb/uvc/uvc_video.c > > > +++ b/drivers/media/usb/uvc/uvc_video.c > > > @@ -79,6 +79,22 @@ int uvc_query_ctrl(struct uvc_device *dev, u8 query, u8 unit, > > > if (likely(ret == size)) > > > return 0; > > > > > > + /* > > > + * In UVC the data is usually represented in little-endian. > > > > I had a comment about this in the previous version, did you ignore it on > > purpose because you disagreed, or was it an oversight ? > > I rephrased the comment. I added "usually" to make it clear that it > might not be the case for all the data types. Like composed or xu. Ah, that's what you meant by "usually". I read it as "usually in little-endian, but could be big-endian too", which confused me. Data types that are not integers will not work nicely with the workaround below. How do you envision that being handled ? Do you consider that the device will return too few bytes only for integer data types, or that affected devices don't have controls that use compound data types ? I don't see what else we could do so I'd be fine with such a heuristic for this workaround, but it needs to be clearly explained. > I also r/package/packet/ > > Did I miss another comment? > > > > + * Some devices return shorter USB control packets that expected if the > > > + * returned value can fit in less bytes. Zero all the bytes that the > > > + * device have not written. > > > > s/have/has/ > > > > And if you meant to start a new paragraph here, a blank line is missing. > > Otherwise, no need to break the line before 80 columns. > > The patch is already in the uvc tree. How do you want to handle this? The branch shared between Hans and me can be rebased, it's a staging area. > > > + * We exclude UVC_GET_INFO from the quirk. UVC_GET_LEN does not need to > > > + * be excluded because its size is always 1. > > > + */ > > > + if (ret > 0 && query != UVC_GET_INFO) { > > > + memset(data + ret, 0, size - ret); > > > + dev_warn_once(&dev->udev->dev, > > > + "UVC non compliance: %s control %u on unit %u returned %d bytes when we expected %u.\n", > > > + uvc_query_name(query), cs, unit, ret, size); > > > + return 0; > > > + } > > > + > > > if (ret != -EPIPE) { > > > dev_err(&dev->udev->dev, > > > "Failed to query (%s) UVC control %u on unit %u: %d (exp. %u).\n", -- Regards, Laurent Pinchart