Hi guys, Following the discussion on the matter of i2c-gpio performance, I'm submitting this very simple patch which adds i2c-bit-platform. Using this driver, a platform can register callbacks called by i2c-bit-algo so that it can modify GPIO pins directly or do pretty much anything else. Besides style, I see 2 points for discussion:
1) Should the i2c-bit-platform call setscl/setsda passing state to 1 (so that SDA/SCL are explicitly pulled high) on probe or should this be implemented in the platforms which mandate this? In the patch I left it up to the platform. 2) Which platform_data structure is passed to the driver? There are three options: 2.a) Currently in the patch - just expect a i2c_algo_bit_data structure. No new structures introduced, but this does expose some underlying bit-algo detail to the platform and does not elegantly support passing any future i2c-bit-platform specific fields, should they be required. 2.b) Declare a new platform structure which has a i2c_algo_bit_data member (for supporting future i2c-bit-platform fields). Solves the future field issue but still exposes so bit-algo stuff to the platform 2.c) Declare a new platform structure with members similar to i2c_algo_bit_data, but only those who should be exposed to the platform. The only downside to this is that any future change to i2c_algo_bit_data may require change to this new platform structure. Tested on an MPC875 running @ 50MHz to achieve near perfect 100kHz I2C. Eran Signed-off-by: Eran Duchan <[email protected]> --- drivers/i2c/busses/Kconfig | 10 +++ drivers/i2c/busses/Makefile | 1 + drivers/i2c/busses/i2c-bit-platform.c | 105 +++++++++++++++++++++++++++++++++ 3 files changed, 116 insertions(+), 0 deletions(-) create mode 100644 drivers/i2c/busses/i2c-bit-platform.c diff --git a/drivers/i2c/busses/Kconfig b/drivers/i2c/busses/Kconfig index 3a6321c..f6c6b8c 100644 --- a/drivers/i2c/busses/Kconfig +++ b/drivers/i2c/busses/Kconfig @@ -365,6 +365,16 @@ config I2C_GPIO This is a very simple bitbanging I2C driver utilizing the arch-neutral GPIO API to control the SCL and SDA lines. +config I2C_BIT_PLATFORM + tristate "I2c-bit-algo as platform device" + select I2C_ALGOBIT + help + An I2C bus adapter which delegates the bit-algo callback registration + to the platform. Useful in cases where existing adapters such as + i2c-gpio are too slow. Keep in mind that no resource locking of any kind + is performed by the adapter or algo, so any such contention must be + handled by the platform. + config I2C_HIGHLANDER tristate "Highlander FPGA SMBus interface" depends on SH_HIGHLANDER diff --git a/drivers/i2c/busses/Makefile b/drivers/i2c/busses/Makefile index 84cb16a..65bced4 100644 --- a/drivers/i2c/busses/Makefile +++ b/drivers/i2c/busses/Makefile @@ -35,6 +35,7 @@ obj-$(CONFIG_I2C_CPM) += i2c-cpm.o obj-$(CONFIG_I2C_DAVINCI) += i2c-davinci.o obj-$(CONFIG_I2C_DESIGNWARE) += i2c-designware.o obj-$(CONFIG_I2C_GPIO) += i2c-gpio.o +obj-$(CONFIG_I2C_BIT_PLATFORM) += i2c-bit-platform.o obj-$(CONFIG_I2C_HIGHLANDER) += i2c-highlander.o obj-$(CONFIG_I2C_IBM_IIC) += i2c-ibm_iic.o obj-$(CONFIG_I2C_IMX) += i2c-imx.o diff --git a/drivers/i2c/busses/i2c-bit-platform.c b/drivers/i2c/busses/i2c-bit-platform.c new file mode 100644 index 0000000..cb98006 --- /dev/null +++ b/drivers/i2c/busses/i2c-bit-platform.c @@ -0,0 +1,105 @@ +/* + i2c-bit-algo as platform device + Delegates the bit-algo callback registration to the platform + + Copyright (C) 2011 Eran Duchan <[email protected]> + + This program is free software; you can redistribute it and/or modify + it under the terms of the GNU General Public License as published by + the Free Software Foundation; either version 2 of the License, or + (at your option) any later version. +*/ + +#include <linux/i2c.h> +#include <linux/i2c-algo-bit.h> +#include <linux/slab.h> + +static int __devinit i2c_bit_platform_probe(struct platform_device *pdev) +{ + struct i2c_algo_bit_data *bit_data; + struct i2c_adapter *adap; + int ret; + + if (pdev->dev.platform_data == NULL) + ret = -ENXIO; + + bit_data = pdev->dev.platform_data; + + ret = -ENOMEM; + adap = kzalloc(sizeof(struct i2c_adapter), GFP_KERNEL); + if (adap == NULL) + goto err_alloc_adap; + + adap->owner = THIS_MODULE; + adap->algo_data = bit_data; + adap->class = I2C_CLASS_HWMON | I2C_CLASS_SPD; + adap->dev.parent = &pdev->dev; + + snprintf(adap->name, sizeof(adap->name), "i2c-bit-platform%d", + pdev->id); + adap->name[sizeof(adap->name) - 1] = '\0'; + + /* + * If "dev->id" is negative we consider it as zero. + * The reason to do so is to avoid sysfs names that only make + * sense when there are multiple adapters. + */ + adap->nr = (pdev->id != -1) ? pdev->id : 0; + ret = i2c_bit_add_numbered_bus(adap); + if (ret) + goto err_add_bus; + + platform_set_drvdata(pdev, adap); + + return 0; + +err_add_bus: +err_alloc_adap: + + kfree(adap); + + return ret; +} + +static int __devexit i2c_bit_platform_remove(struct platform_device *pdev) +{ + struct i2c_adapter *adap; + + adap = platform_get_drvdata(pdev); + + i2c_del_adapter(adap); + kfree(adap); + + return 0; +} + +static struct platform_driver i2c_bit_platform_driver = { + .driver = { + .name = "i2c-bit-platform", + .owner = THIS_MODULE, + }, + .probe = i2c_bit_platform_probe, + .remove = __devexit_p(i2c_bit_platform_remove), +}; + +static int __init i2c_bit_platform_init(void) +{ + int ret; + + ret = platform_driver_register(&i2c_bit_platform_driver); + if (ret) + printk(KERN_ERR "i2c-bit-platform: probe failed: %d\n", ret); + + return ret; +} +subsys_initcall(i2c_bit_platform_init); + +static void __exit i2c_bit_platform_exit(void) +{ + platform_driver_unregister(&i2c_bit_platform_driver); +} +module_exit(i2c_bit_platform_exit); + +MODULE_AUTHOR("Eran Duchan <[email protected]>"); +MODULE_DESCRIPTION("Thin platform adapter for i2c-bit-algo"); +MODULE_LICENSE("GPL"); -- 1.7.0.4 -- To unsubscribe from this list: send the line "unsubscribe linux-i2c" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html
