Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753571AbYCLM1z (ORCPT ); Wed, 12 Mar 2008 08:27:55 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751533AbYCLM1s (ORCPT ); Wed, 12 Mar 2008 08:27:48 -0400 Received: from rtsoft3.corbina.net ([85.21.88.6]:26084 "EHLO buildserver.ru.mvista.com" rhost-flags-OK-FAIL-OK-FAIL) by vger.kernel.org with ESMTP id S1751206AbYCLM1s (ORCPT ); Wed, 12 Mar 2008 08:27:48 -0400 Date: Wed, 12 Mar 2008 15:27:46 +0300 From: Anton Vorontsov To: David Brownell Cc: Andrew Morton , linux-kernel@vger.kernel.org Subject: Re: [PATCH 1/3] gpiolib: implement dynamic base allocation Message-ID: <20080312122746.GB500@localhost.localdomain> Reply-To: avorontsov@ru.mvista.com References: <20080311174116.GA12397@localhost.localdomain> <200803111349.29166.david-b@pacbell.net> Mime-Version: 1.0 Content-Type: text/plain; charset=utf8 Content-Disposition: inline In-Reply-To: <200803111349.29166.david-b@pacbell.net> User-Agent: Mutt/1.4.2.2i Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 4121 Lines: 131 On Tue, Mar 11, 2008 at 12:49:28PM -0800, David Brownell wrote: > On Tuesday 11 March 2008, Anton Vorontsov wrote: > > If gpio_chip->base is negative during registration, gpiolib requests > > dynamic base allocation. This is useful for devices being registered > > at run-time (in contrast to platform devices). > > The issue isn't runtime or platform_device ... it's whether the > numbers are defined by the board/platform, versus on-the fly. > I2C and FPGA based expanders may be part of the board, and thus > use static assignment, for just one example. So: > > ... This dynamic allocation of GPIO numbers is useful > for devices that aren't always present, such as GPIOs > from expanders on add-in cards rather than mainboards. > > > To avoid reusing any numbers that may have been explicitly assigned, > > but not yet registered, dynamic gpio base allocator will assign GPIO > > numbers from the biggest number on down, instead of from the smallest > > on up. > > > > Signed-off-by: Anton Vorontsov > > Acked-by: David Brownell > > ... given commit comment fixup as above, since that's the only > documentation just now. Thanks, below is the patch with updated log. - - - - From: Anton Vorontsov Subject: gpiolib: implement dynamic base allocation If gpio_chip->base is negative during registration, gpiolib requests dynamic base allocation. This is useful for devices that aren't always present, such as GPIOs from expanders on add-in cards rather than mainboards. To avoid reusing any numbers that may have been explicitly assigned, but not yet registered, dynamic gpio base allocator will assign GPIO numbers from the biggest number on down, instead of from the smallest on up. Signed-off-by: Anton Vorontsov Acked-by: David Brownell --- drivers/gpio/gpiolib.c | 43 ++++++++++++++++++++++++++++++++++++++----- 1 files changed, 38 insertions(+), 5 deletions(-) diff --git a/drivers/gpio/gpiolib.c b/drivers/gpio/gpiolib.c index 623fcd9..81d81c9 100644 --- a/drivers/gpio/gpiolib.c +++ b/drivers/gpio/gpiolib.c @@ -80,6 +80,33 @@ static inline struct gpio_chip *gpio_to_chip(unsigned gpio) return gpio_desc[gpio].chip; } +static int gpiochip_find_base(int ngpio) +{ + int i; + int spare = 0; + int base = -ENOSPC; + + for (i = ARCH_NR_GPIOS - 1; i >= 0 ; i--) { + struct gpio_chip *chip = gpio_desc[i].chip; + + if (!chip) { + spare++; + if (spare == ngpio) { + base = i; + break; + } + } else { + spare = 0; + i -= chip->ngpio - 1; + } + } + + if (gpio_is_valid(base)) + pr_debug("%s: found new base at %d\n", __func__, base); + + return base; +} + /** * gpiochip_add() - register a gpio_chip * @chip: the chip to register, with chip->base initialized @@ -95,17 +122,22 @@ int gpiochip_add(struct gpio_chip *chip) int status = 0; unsigned id; - /* NOTE chip->base negative is reserved to mean a request for - * dynamic allocation. We don't currently support that. - */ - - if (chip->base < 0 || !gpio_is_valid(chip->base + chip->ngpio)) { + if (gpio_is_valid(chip->base) && + !gpio_is_valid(chip->base + chip->ngpio)) { status = -EINVAL; goto fail; } spin_lock_irqsave(&gpio_lock, flags); + if (!gpio_is_valid(chip->base)) { + chip->base = gpiochip_find_base(chip->ngpio); + if (!gpio_is_valid(chip->base)) { + status = chip->base; + goto fail_unlock; + } + } + /* these GPIO numbers must not be managed by another gpio_chip */ for (id = chip->base; id < chip->base + chip->ngpio; id++) { if (gpio_desc[id].chip != NULL) { @@ -120,6 +152,7 @@ int gpiochip_add(struct gpio_chip *chip) } } +fail_unlock: spin_unlock_irqrestore(&gpio_lock, flags); fail: /* failures here can mean systems won't boot... */ -- 1.5.2.2 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/