From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mgamail.intel.com (mgamail.intel.com [192.198.163.17]) (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 7E5DE38DE1 for ; Thu, 10 Oct 2024 15:16:22 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=192.198.163.17 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1728573384; cv=none; b=uvBZ/hvRf5nUddztRC0AA0x+DveYx1TAUURReJ6leqSxGKlh5Oyu1xzjgNFiqpaRiFE6puwzNwe6h0PM1wZXTo+A4h5skS3Lz+7annbnwWBnvXY/ap4fnd7VfrCHv62vetegQv9W6/VVvRnFoRZFwGjHvw7C1WNxW6xSCy5Worg= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1728573384; c=relaxed/simple; bh=3r7XjWCd7n9+cKPDndkUACyizjbXDe/S2rPom65uPUI=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=mXKiSf3/9bThjzqGOoZd6EIxBK1qKn2ShNb9qdDBJ/cH5ob+JZL3zYCWy/ORxj5wJ9wSU9C8FYv/CymlAy5XlhcaiJGxW4A79n4QDSiPorOUqK73dJef6YV3Yy5pHkTktuZuOtbjRoCA/Bqtz+KGZxMyCIMbBgukMyiI4EEqaQc= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.intel.com; spf=none smtp.mailfrom=linux.intel.com; dkim=pass (2048-bit key) header.d=intel.com header.i=@intel.com header.b=aDKhUki1; arc=none smtp.client-ip=192.198.163.17 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.intel.com Authentication-Results: smtp.subspace.kernel.org; spf=none smtp.mailfrom=linux.intel.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=intel.com header.i=@intel.com header.b="aDKhUki1" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1728573383; x=1760109383; h=date:from:to:cc:subject:message-id:references: mime-version:in-reply-to; bh=3r7XjWCd7n9+cKPDndkUACyizjbXDe/S2rPom65uPUI=; b=aDKhUki1LFSCDxmxuMyNa0ekR+Mmmlz3cVhVUxfVCRzR14arOG++WTq3 fTe/C4zsYf70EpKaDKEl2PTtzt0ymc8iqEGG8kUHH+tIl2c867e2Zr0A8 xxXTPA6lzSDd/aG/TJoDt6XI/QA3eY2aRbq6Zr5Ml8PHtquuNI+O34Zf5 pS7hKkcGvxqaDawyd0dl0aB+I9Ig93kwhF3ywWSCtm5vgtOUZkakqV3n5 1I/WDAenB/QkMEjBvWgG2Nx06DH4tHY+2f5vUihRmtb7THA2sHVjBBm0c ZolTVwuDh2oZriXRikUg1AWh0blrwpC6myR4REfgQgVGMKjRFXD6ykwEJ g==; X-CSE-ConnectionGUID: vMT1txADQR+OoYyOOVMB5g== X-CSE-MsgGUID: NKCkhdSuTXetlGRkQ2rMVg== X-IronPort-AV: E=McAfee;i="6700,10204,11220"; a="27810878" X-IronPort-AV: E=Sophos;i="6.11,193,1725346800"; d="scan'208";a="27810878" Received: from orviesa003.jf.intel.com ([10.64.159.143]) by fmvoesa111.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 10 Oct 2024 08:16:17 -0700 X-CSE-ConnectionGUID: TnDZstXQSZeeixD90okhAA== X-CSE-MsgGUID: ALlT+SXEQ2qwUWC6WyZnRw== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="6.11,193,1725346800"; d="scan'208";a="81439049" Received: from smile.fi.intel.com ([10.237.72.154]) by orviesa003.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 10 Oct 2024 08:16:13 -0700 Received: from andy by smile.fi.intel.com with local (Exim 4.98) (envelope-from ) id 1syutc-00000001Zgw-2s69; Thu, 10 Oct 2024 18:16:08 +0300 Date: Thu, 10 Oct 2024 18:16:08 +0300 From: Andy Shevchenko To: Chen-Yu Tsai Cc: Rob Herring , Saravana Kannan , Matthias Brugger , AngeloGioacchino Del Regno , Wolfram Sang , Benson Leung , Tzung-Bi Shih , chrome-platform@lists.linux.dev, devicetree@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-mediatek@lists.infradead.org, linux-kernel@vger.kernel.org, Douglas Anderson , Johan Hovold , Jiri Kosina , linux-i2c@vger.kernel.org Subject: Re: [PATCH v8 4/8] i2c: Introduce OF component probe function Message-ID: References: <20241008073430.3992087-1-wenst@chromium.org> <20241008073430.3992087-5-wenst@chromium.org> Precedence: bulk X-Mailing-List: chrome-platform@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20241008073430.3992087-5-wenst@chromium.org> Organization: Intel Finland Oy - BIC 0357606-4 - Westendinkatu 7, 02160 Espoo On Tue, Oct 08, 2024 at 03:34:23PM +0800, Chen-Yu Tsai wrote: > Some devices are designed and manufactured with some components having > multiple drop-in replacement options. These components are often > connected to the mainboard via ribbon cables, having the same signals > and pin assignments across all options. These may include the display > panel and touchscreen on laptops and tablets, and the trackpad on > laptops. Sometimes which component option is used in a particular device > can be detected by some firmware provided identifier, other times that > information is not available, and the kernel has to try to probe each > device. > > This change attempts to make the "probe each device" case cleaner. The > current approach is to have all options added and enabled in the device > tree. The kernel would then bind each device and run each driver's probe > function. This works, but has been broken before due to the introduction > of asynchronous probing, causing multiple instances requesting "shared" > resources, such as pinmuxes, GPIO pins, interrupt lines, at the same > time, with only one instance succeeding. Work arounds for these include > moving the pinmux to the parent I2C controller, using GPIO hogs or > pinmux settings to keep the GPIO pins in some fixed configuration, and > requesting the interrupt line very late. Such configurations can be seen > on the MT8183 Krane Chromebook tablets, and the Qualcomm sc8280xp-based > Lenovo Thinkpad 13S. > > Instead of this delicate dance between drivers and device tree quirks, > this change introduces a simple I2C component probe function. For a > given class of devices on the same I2C bus, it will go through all of > them, doing a simple I2C read transfer and see which one of them responds. > It will then enable the device that responds. > > This requires some minor modifications in the existing device tree. The > status for all the device nodes for the component options must be set > to "fail-needs-probe". This makes it clear that some mechanism is > needed to enable one of them, and also prevents the prober and device > drivers running at the same time. Fresh reading of the commit message make me think why the firmware or bootloader on such a device can't form a dynamic OF (overlay?) to fulfill the need? Another question is that we have the autoprobing mechanism for I2C for ages, why that one can't be (re-)used / extended to cover these cases? ... > +#ifndef _LINUX_I2C_OF_PROBER_H > +#define _LINUX_I2C_OF_PROBER_H Missing kconfig.h. > +struct device; > +struct device_node; > + > +/** > + * struct i2c_of_probe_ops - I2C OF component prober callbacks > + * > + * A set of callbacks to be used by i2c_of_probe_component(). > + * > + * All callbacks are optional. Callbacks are called only once per run, and are > + * used in the order they are defined in this structure. > + * > + * All callbacks that have return values shall return %0 on success, > + * or a negative error number on failure. > + * > + * The @dev parameter passed to the callbacks is the same as @dev passed to > + * i2c_of_probe_component(). It should only be used for dev_printk() calls > + * and nothing else, especially not managed device resource (devres) APIs. > + */ > +struct i2c_of_probe_ops { > + /** > + * @enable: Retrieve and enable resources so that the components respond to probes. > + * > + * Resources should be reverted to their initial state before returning if this fails. > + */ > + int (*enable)(struct device *dev, struct device_node *bus_node, void *data); > + > + /** > + * @cleanup_early: Release exclusive resources prior to enabling component. > + * > + * Only called if a matching component is actually found. If none are found, > + * resources that would have been released in this callback should be released in > + * @free_resourcs_late instead. > + */ > + void (*cleanup_early)(struct device *dev, void *data); > + > + /** > + * @cleanup: Opposite of @enable to balance refcounts and free resources after probing. > + * > + * Should check if resources were already freed by @cleanup_early. > + */ > + void (*cleanup)(struct device *dev, void *data); > +}; > + > +/** > + * struct i2c_of_probe_cfg - I2C OF component prober configuration > + * @ops: Callbacks for the prober to use. > + * @type: A string to match the device node name prefix to probe for. > + */ > +struct i2c_of_probe_cfg { > + const struct i2c_of_probe_ops *ops; > + const char *type; > +}; > + > +#if IS_ENABLED(CONFIG_OF_DYNAMIC) > + > +int i2c_of_probe_component(struct device *dev, const struct i2c_of_probe_cfg *cfg, void *ctx); > + > +#endif /* IS_ENABLED(CONFIG_OF_DYNAMIC) */ > + > +#endif /* _LINUX_I2C_OF_PROBER_H */ -- With Best Regards, Andy Shevchenko