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 1EEE92B9C6 for ; Sun, 20 Oct 2024 14:36:36 +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=1729434998; cv=none; b=fd+YOUietifIiddOzc9yYlPYN3AupDD6bffr4QTv+2c6SFLGDc+/KKZXQMoy7LpoHKbWvP4JUwNClBCbHPZcLoBBYwM5ostP6v1iWxyCXluLQOu9ATGnKOkAAeWxrobI4cicBLlXumXJemyFmN9HRWjzHEtrj2harqSmT8VY+ac= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1729434998; c=relaxed/simple; bh=0sSBQ0AgvT+5mlAQvbezHnEfs7nP96DG1KzWG5CPujY=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=YYP0Cyv++ojPDzh4bSwrH6BF0e/uriWpX0wJtQk0+k+mCYrUNYzjSJKhNfpsIkdQ7CvtrIfrxitmVVA1U0Q31AZ0N+8n/mMtkFl49r13vK8n4bodOnyA63n4hraupqs+QHhPgf9HRTBkYMo41KUuaEPZsUiTsXtRZ2Thgxt0VFQ= 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=Py/oGZgR; 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="Py/oGZgR" Received: from pendragon.ideasonboard.com (81-175-209-231.bb.dnainternet.fi [81.175.209.231]) by perceval.ideasonboard.com (Postfix) with ESMTPSA id 6ED2D502; Sun, 20 Oct 2024 16:34:49 +0200 (CEST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=ideasonboard.com; s=mail; t=1729434889; bh=0sSBQ0AgvT+5mlAQvbezHnEfs7nP96DG1KzWG5CPujY=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=Py/oGZgRYQN8xaY/A5rPKNv2qUhlbp7iRFUkhexVD9pti9kuOUOv7DOc6f7Fio99A uxUAu/fCjwmM/6cAE8kINRCARQCJ6q/LX/sqXv6cZUiijKWE75TU0MIBx0F/eCLNDz kOG3EvFeHPktGgf6TmhiATDz2QA0Jy3TXVUwTk94= Date: Sun, 20 Oct 2024 17:36:29 +0300 From: Laurent Pinchart To: Greg KH Cc: Geert Uytterhoeven , Douglas Anderson , Linus Walleij , Andrzej Hajda , Neil Armstrong , Robert Foss , Jonas Karlman , Jernej Skrabec , Maarten Lankhorst , Maxime Ripard , Thomas Zimmermann , David Airlie , Simona Vetter , dri-devel@lists.freedesktop.org, linux-renesas-soc@vger.kernel.org Subject: Re: [PATCH] drm/bridge: ti-sn65dsi86: Fix multiple instances Message-ID: <20241020143629.GC28934@pendragon.ideasonboard.com> References: <8c2df6a903f87d4932586b25f1d3bd548fe8e6d1.1729180470.git.geert+renesas@glider.be> <20241018131035.GA20602@pendragon.ideasonboard.com> <2024101855-judo-tattered-bc3c@gregkh> <20241018142522.GA28934@pendragon.ideasonboard.com> <2024101837-crushed-emphasis-b496@gregkh> Precedence: bulk X-Mailing-List: linux-renesas-soc@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <2024101837-crushed-emphasis-b496@gregkh> On Fri, Oct 18, 2024 at 04:31:21PM +0200, Greg KH wrote: > On Fri, Oct 18, 2024 at 05:25:22PM +0300, Laurent Pinchart wrote: > > On Fri, Oct 18, 2024 at 04:09:26PM +0200, Greg KH wrote: > > > On Fri, Oct 18, 2024 at 03:36:48PM +0200, Geert Uytterhoeven wrote: > > > > On Fri, Oct 18, 2024 at 3:10 PM Laurent Pinchart wrote: > > > > > On Fri, Oct 18, 2024 at 09:45:52AM +0200, Geert Uytterhoeven wrote: > > > > > > Each bridge instance creates up to four auxiliary devices with different > > > > > > names. However, their IDs are always zero, causing duplicate filename > > > > > > errors when a system has multiple bridges: > > > > > > > > > > > > sysfs: cannot create duplicate filename '/bus/auxiliary/devices/ti_sn65dsi86.gpio.0' > > > > > > > > > > > > Fix this by using a unique instance ID per bridge instance. > > > > > > > > > > Isn't this something that should be handled by the AUX core ? The code > > > > > below would otherwise need to be duplicated by all drivers, which seems > > > > > a burden we should avoid. > > > > > > > > According to the documentation, this is the responsibility of the caller > > > > https://elixir.bootlin.com/linux/v6.11.4/source/include/linux/auxiliary_bus.h#L81 > > > > I believe this is the same for platform devices. > > > > See also the example at > > > > https://elixir.bootlin.com/linux/v6.11.4/source/include/linux/auxiliary_bus.h#L116 > > > > > > > > Note: the platform bus supports PLATFORM_DEVID_AUTO, but the auxiliary > > > > bus does not. > > > > > > Yes, it does not as it's up to the caller to create a unique name, like > > > your patch here does. I'd argue that platform should also not do > > > automatic device ids, but that's a different argument :) > > > > __auxiliary_device_add() creates the device name with > > > > dev_set_name(dev, "%s.%s.%d", modname, auxdev->name, auxdev->id); > > > > I'm not calling for a PLATFORM_DEVID_AUTO-like feature here, but > > shouldn't the first component of the device name use the parent's name > > instead of the module name ? > > Why would the parent's name not be the module name? That name is > guaranteed unique in the system. If you want "uniqueness" within the > driver/module, use the name and id field please. > > That's worked well so far, but to be fair, aux devices are pretty new. > What problem is this naming scheme causing? Auxiliary devices are created as children of a parent device. When multiple instances of the same parent type exist, this will be reflected in the /sys/devices/ devices tree hierarchy without any issue. The problem comes from the fact the the auxiliary devices need a unique name for /sys/bus/auxialiary/devices/, where we somehow have to differenciate devices of identical types. Essentially, we're trying to summarize a whole hierarchy (path in /sys/devices/) into a single string. There are different ways to solve this. For platform devices, we use a device ID. For I2C devices, we use the parent's bus number. Other buses use different schemes. Geert's patch implements a mechanism in the ti-sn65dsi86 driver to handle this, and assign an id managed by the parent. In a sense we could consider this to be similar to what is done for I2C, where the bus number is also a property of the parent. However, the big difference is that the I2C bus number is managed by the I2C subsystem, while here the id is managed by the ti-sn65dsi86 driver, not by the auxiliary device core. This would require duplicating the same mechanism in every single driver creating auxiliary devices. This strikes me as a fairly bad idea. The problem should be solved by the core, not by individual drivers. -- Regards, Laurent Pinchart