From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753335Ab2KPT6Q (ORCPT ); Fri, 16 Nov 2012 14:58:16 -0500 Received: from ogre.sisk.pl ([193.178.161.156]:49505 "EHLO ogre.sisk.pl" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751495Ab2KPT6O (ORCPT ); Fri, 16 Nov 2012 14:58:14 -0500 From: "Rafael J. Wysocki" To: Mika Westerberg Cc: Jean Delvare , ben-linux@fluff.org, w.sang@pengutronix.de, linux-kernel@vger.kernel.org, lenb@kernel.org, rafael.j.wysocki@intel.com, broonie@opensource.wolfsonmicro.com, grant.likely@secretlab.ca, linus.walleij@linaro.org, bhelgaas@google.com, mathias.nyman@linux.intel.com, linux-acpi@vger.kernel.org Subject: Re: [PATCH v2 3/3] i2c / ACPI: add ACPI enumeration support Date: Fri, 16 Nov 2012 21:02:36 +0100 Message-ID: <5908031.ZEcDQlG5EW@vostro.rjw.lan> User-Agent: KMail/4.8.5 (Linux/3.7.0-rc5; KDE/4.8.5; x86_64; ; ) In-Reply-To: <20121116141729.GS17774@intel.com> References: <1352977397-2280-1-git-send-email-mika.westerberg@linux.intel.com> <20121116144256.55b49cae@endymion.delvare> <20121116141729.GS17774@intel.com> MIME-Version: 1.0 Content-Transfer-Encoding: 7Bit Content-Type: text/plain; charset="utf-8" Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Friday, November 16, 2012 04:17:29 PM Mika Westerberg wrote: > On Fri, Nov 16, 2012 at 02:42:56PM +0100, Jean Delvare wrote: > > On Fri, 16 Nov 2012 14:21:54 +0100, Rafael J. Wysocki wrote: > > > On Friday, November 16, 2012 02:03:57 PM Jean Delvare wrote: > > > > Hi Rafael, > > > > > > > > On Fri, 16 Nov 2012 11:09:03 +0100, Rafael J. Wysocki wrote: > > > > > On Thursday, November 15, 2012 01:03:17 PM Mika Westerberg wrote: > > > > > > ACPI 5 introduced I2cSerialBus resource that makes it possible to enumerate > > > > > > and configure the I2C slave devices behind the I2C controller. This patch > > > > > > adds helper functions to support I2C slave enumeration. > > > > > > > > > > > > An ACPI enabled I2C controller driver only needs to call acpi_i2c_register_devices() > > > > > > in order to get its slave devices enumerated, created and bound to the > > > > > > corresponding ACPI handle. > > > > > > > > > > > > Signed-off-by: Mika Westerberg > > > > > > > > > > Are there any objections against this patch or comments? > > > > > > > > > > Worfram? Jean? Ben? > > > > > > > > I am no longer maintaining the i2c subsystem and will not have the time > > > > to look deeply into this. All I can say is that I very happy to see > > > > this finally happen. Maybe with ACPI 5.0 we will finally be done with > > > > resource conflicts plaguing many systems for several years now. > > > > > > > > I took a quick look, and the only thing which seems suspicious is this > > > > function: > > > > > > > > > +static int acpi_i2c_find_child_address(struct acpi_resource *ares, void *data) > > > > > +{ > > > > > + struct acpi_resource_i2c_serialbus *sb; > > > > > + struct acpi_i2c_find *i2c_find = data; > > > > > + > > > > > + if (ares->type != ACPI_RESOURCE_TYPE_SERIAL_BUS) > > > > > + return 1; > > > > > + > > > > > + sb = &ares->data.i2c_serial_bus; > > > > > + if (sb->type != ACPI_RESOURCE_SERIAL_TYPE_I2C) > > > > > + return 1; > > > > > + > > > > > + if (sb->slave_address == i2c_find->addr) > > > > > > > > The 7-bit and 10-bit address maps overlap, so the above isn't enough. > > > > You must compare the addresses _and_ sb->access_mode with > > > > i2c_find->access_mode (which needs to be added and filled properly.) > > Ok. I wasn't sure about that and given that 10-bit addresses are not that > common I tought that we can just compare the addr to zero. I'll add the > check. > > > > > > > > > > + i2c_find->found = true; > > > > > + > > > > > + return 1; > > > > > +} > > > > > > > > Plus, it seems odd that this function always returns 1. > > > > > > Yes, this is a bug I think. Mika? > > > > The equivalent function for SPI devices does the same, so if this is a > > bug, it must be fixed there too. If this is not a bug then it is > > questionable why these functions return something in the first place. > > > > But then again I didn't look into the design, so I may be missing > > something. > > It is not a bug, it just means that we don't want the ACPI core to fill in > normal resources (we only want to peek the ACPI resources and find the > corresponding I2CSerialBus() resource). Ah, that's what's called by acpi_dev_get_resources(). But what about writing it this way: static int acpi_i2c_find_child_address(struct acpi_resource *ares, void *data) { if (ares->type == ACPI_RESOURCE_TYPE_SERIAL_BUS) { struct acpi_resource_i2c_serialbus *sb; sb = &ares->data.i2c_serial_bus; if (sb->type == ACPI_RESOURCE_SERIAL_TYPE_I2C) { struct acpi_i2c_find *i2c_find = data; if (sb->slave_address == i2c_find->addr) i2c_find->found = true; } } /* Tell the ACPI core to skip this resource. */ return 1; } Seems easier to follow. :-) Thanks, Rafael -- I speak only for myself. Rafael J. Wysocki, Intel Open Source Technology Center.