From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1163153AbcKAGOV (ORCPT ); Tue, 1 Nov 2016 02:14:21 -0400 Received: from mail-oi0-f41.google.com ([209.85.218.41]:32907 "EHLO mail-oi0-f41.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1163135AbcKAGOT (ORCPT ); Tue, 1 Nov 2016 02:14:19 -0400 From: Phong Vo MIME-Version: 1.0 X-Mailer: Microsoft Office Outlook 12.0 Thread-Index: AdI0BcIgO6427efbRNWi1/qk2UMzDQ== Date: Tue, 1 Nov 2016 13:14:16 +0700 Message-ID: <8a69cdff155793e8e687d527d9ace97f@mail.gmail.com> Subject: Re: [RFC v2 2/2] i2c: Pass i2c_device_id to probe func when using DT ids through ACPI To: mika.westerberg@linux.intel.com, leonard.crestez@intel.com Cc: wsa+renesas@sang-engineering.com, rafael.j.wysocki@intel.com, len.brown@intel.com, irina.tirdea@intel.com, octavian.purdila@intel.com, daniel.baluta@intel.com, linux-kernel@vger.kernel.org, linux-acpi@vger.kernel.org, linux-i2c@vger.kernel.org, Tin Huynh , Loc Ho , patches@apm.com Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Transfer-Encoding: 8bit X-MIME-Autoconverted: from quoted-printable to 8bit by mail.home.local id uA16G1Dm001373 >From: Mika Westerberg >Subject: Re: [RFC v2 2/2] i2c: Pass i2c_device_id to probe func when using DT ids through ACPI >Date: Monday 13th June 2016 09:26:55 UTC (5 months ago) > >On Fri, Jun 10, 2016 at 06:57:36PM +0300, Crestez Dan Leonard wrote: >> 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; >>  }> > >Yes, that's what I mean. > >> The biggest concern is that this would change the i2c device name >> between kernel versions. Is that acceptable? > >I don't think that is a problem since I still have not seen a single >system using ACPI _DSD so I would not expect anything to break. > >However, I'm still not convinced it is good idea to return i2c_device_id >from a completely different table if we match using ACPI/DT table. All, Is there a conclusion on this? We have been tackling the same issue and incidentally arrived at a similar solution as like Lenard proposed  in the patch above.