Doug, On Tue, Apr 09, 2013 at 02:34:28PM -0700, Doug Anderson wrote: > The i2c-arb-gpio-challenge driver implements an I2C arbitration scheme > where masters need to claim the bus with a GPIO before they can start > a transcation. This should generally only be used when standard I2C > multimaster isn't appropriate for some reason (errata/bugs). > > This driver is based on code that Simon Glass added to the i2c-s3c2410 > driver in the Chrome OS kernel 3.4 tree. The current incarnation as a > mux driver is as suggested by Grant Likely. See > <https://patchwork.kernel.org/patch/1877311/> for some history. > > Signed-off-by: Doug Anderson <dianders@xxxxxxxxxxxx> > Signed-off-by: Simon Glass <sjg@xxxxxxxxxxxx> > Signed-off-by: Naveen Krishna Chatradhi <ch.naveen@xxxxxxxxxxx> > Reviewed-by: Stephen Warren <swarren@xxxxxxxxxx> Mostly good, except for some documentation updates. > diff --git a/Documentation/devicetree/bindings/i2c/i2c-arb-gpio-challenge.txt b/Documentation/devicetree/bindings/i2c/i2c-arb-gpio-challenge.txt > new file mode 100644 > index 0000000..726e099 > --- /dev/null > +++ b/Documentation/devicetree/bindings/i2c/i2c-arb-gpio-challenge.txt > @@ -0,0 +1,80 @@ > +GPIO-based I2C Arbitration > +========================== > +This uses GPIO lines to arbitrate who is the master of an I2C bus in a > +multimaster situation. "uses GPIO lines and a challange & response mechanism" or something like that. There might be other GPIO based arbitrations in the future (though I hope there won't). > + > +In many cases using GPIOs to arbitrate is not needed and a design can use > +the standard I2C multi-master rules. Using GPIOs is generally useful in > +the case where there is a device on the bus that has errata and/or bugs > +that makes standard multimaster mode not feasible. I like this paragraph! ... > +- their-claim-gpios: The GPIOs that the other sides use the claim the bus. > + Note that some implementations may only support a single other master. Stronger? "Currently, only one other master is supported"? ... > diff --git a/drivers/i2c/muxes/Kconfig b/drivers/i2c/muxes/Kconfig > index 0be5b83..ab4dcaf 100644 > --- a/drivers/i2c/muxes/Kconfig > +++ b/drivers/i2c/muxes/Kconfig > @@ -5,6 +5,17 @@ > menu "Multiplexer I2C Chip support" > depends on I2C_MUX > > +config I2C_ARB_GPIO_CHALLENGE > + tristate "GPIO-based I2C arbitration" > + depends on GENERIC_GPIO && OF > + help > + If you say yes to this option, support will be included for an > + I2C multimaster arbitration scheme using GPIOs where masters have > + to claim the bus by asserting a GPIO. "callenge & response"? ... > diff --git a/drivers/i2c/muxes/i2c-arb-gpio-challenge.c b/drivers/i2c/muxes/i2c-arb-gpio-challenge.c > new file mode 100644 > index 0000000..bda020a > --- /dev/null > +++ b/drivers/i2c/muxes/i2c-arb-gpio-challenge.c > @@ -0,0 +1,252 @@ > +/* > + * GPIO-based I2C Arbitration "callenge & response"? ... > + * > + * Copyright (C) 2012 Google, Inc > + * > + * This software is licensed under the terms of the GNU General Public > + * License version 2, as published by the Free Software Foundation, and > + * may be copied, distributed, and modified under those terms. > + * > + * This program is distributed in the hope that it will be useful, > + * but WITHOUT ANY WARRANTY; without even the implied warranty of > + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the > + * GNU General Public License for more details. > + * > + */ > + > +#include <linux/delay.h> > +#include <linux/gpio.h> > +#include <linux/kernel.h> > +#include <linux/i2c.h> > +#include <linux/i2c-mux.h> > +#include <linux/init.h> > +#include <linux/module.h> > +#include <linux/of_i2c.h> > +#include <linux/of_gpio.h> > +#include <linux/platform_device.h> > +#include <linux/slab.h> > + > + > +/** > + * struct i2c_arbitrator_data - Driver data for I2C arbitrator > + * > + * @parent: Parent adapter > + * @child: Child bus > + * @our_gpio: GPIO we'll use to claim. > + * @our_gpio_release: 0 if active high; 1 if active low; AKA if the GPIO == > + * this then consider it released. > + * @their_gpio: GPIO that the other side will use to claim. > + * @their_gpio_release: 0 if active high; 1 if active low; AKA if the GPIO == > + * this then consider it released. > + * @slew_delay_us: microseconds to wait for a GPIO to go high. > + * @wait_retry_us: we'll attempt another claim after this many microseconds. > + * @wait_free_us: we'll give up after this many microseconds. > + */ > + > +struct i2c_arbitrator_data { > + struct i2c_adapter *parent; > + struct i2c_adapter *child; > + No empty line. > + int our_gpio; > + int our_gpio_release; > + int their_gpio; > + int their_gpio_release; > + unsigned int slew_delay_us; > + unsigned int wait_retry_us; > + unsigned int wait_free_us; > +}; Single space as indentaion after "int". Other than that, looks fine to me. Thanks! -- To unsubscribe from this list: send the line "unsubscribe linux-i2c" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
