From mboxrd@z Thu Jan 1 00:00:00 1970 From: Crestez Dan Leonard Subject: Re: [RFC v2 2/2] i2c: Pass i2c_device_id to probe func when using DT ids through ACPI Date: Fri, 10 Jun 2016 18:57:36 +0300 Message-ID: <6721468a-753d-fb52-5bc5-8738312b7bd0@intel.com> References: <20160610063232.GR1791@lahna.fi.intel.com> Mime-Version: 1.0 Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <20160610063232.GR1791@lahna.fi.intel.com> Sender: linux-acpi-owner@vger.kernel.org To: Mika Westerberg Cc: linux-acpi@vger.kernel.org, "Rafael J. Wysocki" , Len Brown , linux-i2c@vger.kernel.org, Wolfram Sang , linux-kernel@vger.kernel.org, Irina Tirdea , Octavian Purdila , Daniel Baluta List-Id: linux-i2c@vger.kernel.org On 06/10/2016 09:32 AM, Mika Westerberg wrote: > On Thu, Jun 09, 2016 at 04:06:03PM +0300, Crestez Dan Leonard wrote: >> When devices are instatiated through devicetree the i2c_client->name is >> set to the compatible string with company name stripped out. This is >> then matched to the i2c_device_id table to pass the device_id to the >> probe function. This id parameter is used by some device drivers to >> differentiate between model numbers. >> >> When using ACPI this id parameter is NULL and the driver usually needs >> to do ACPI-specific differentiation. >> >> This patch attempts to find a valid i2c_device_id when using ACPI with >> DT-like compatible strings. > > So I don't really understand why it would be good idea to pass > i2c_device_id for devices which are matched against their ACPI/DT > tables. Apparently DT is already doing that so maybe there is some > reason. > > Anyway, why not fill in the device name when it is first enumerated > if it uses DT compatible property? Just like DT does. > This automatic matching of i2c_device_id works for devicetree because of_i2c_register_device sets i2c_board_info.type to the compatible string with the vendor prefix removed. For I2C devices described via ACPI the i2c_board_info.type string is set to the ACPI device name. This ends up something like "PRP0001:00". This could be changed in acpi_i2c_get_info to use the of_compatible string from DSD if present. Is that what you mean? That would work and it would be cleaner than my patch. Something like this: diff --git drivers/i2c/i2c-core.c drivers/i2c/i2c-core.c index 1e0ef9b..ba2fe7f 100644 --- drivers/i2c/i2c-core.c +++ drivers/i2c/i2c-core.c @@ -181,7 +181,24 @@ static int acpi_i2c_get_info(struct acpi_device *adev, acpi_dev_free_resource_list(&resource_list); - strlcpy(info->type, dev_name(&adev->dev), sizeof(info->type)); + /* + * If we have a DT id set info.type to the first compatible string with + * the vendor prefix stripped. This is similar to of_modalias_node + */ + if (adev->data.of_compatible) { + const union acpi_object *obj; + const char *str, *chr; + + obj = adev->data.of_compatible; + if (obj->type == ACPI_TYPE_PACKAGE) + obj = obj->package.elements; + str = obj->string.pointer; + chr = strchr(str, ','); + if (chr) + str = chr + 1; + strlcpy(info->type, str, sizeof(info->type)); + } else + strlcpy(info->type, dev_name(&adev->dev), sizeof(info->type)); return 0; } The biggest concern is that this would change the i2c device name between kernel versions. Is that acceptable?