This is a driver for the imx25 ADC/TSC module. It controls the touchscreen conversion queue and creates a touchscreen input device. The driver currently only supports 4 wire touchscreens. The driver uses a simple conversion queue of precharge, touch detection, X measurement, Y measurement, precharge and another touch detection. This driver uses the regmap from the parent to setup some touch specific settings in the core driver and setup a idle configuration with touch detection. Signed-off-by: Markus Pargmann <mpa@xxxxxxxxxxxxxx> Signed-off-by: Denis Carikli <denis@xxxxxxxxxx> Acked-by: Dmitry Torokhov <dtor@xxxxxxxxxx> Signed-off-by: Markus Pargmann <mpa@xxxxxxxxxxxxxx> --- drivers/input/touchscreen/Kconfig | 6 + drivers/input/touchscreen/Makefile | 1 + drivers/input/touchscreen/fsl-imx25-tcq.c | 587 ++++++++++++++++++++++++++++++ 3 files changed, 594 insertions(+) create mode 100644 drivers/input/touchscreen/fsl-imx25-tcq.c diff --git a/drivers/input/touchscreen/Kconfig b/drivers/input/touchscreen/Kconfig index 58917525126e..f1534a0cd23f 100644 --- a/drivers/input/touchscreen/Kconfig +++ b/drivers/input/touchscreen/Kconfig @@ -748,6 +748,12 @@ config TOUCHSCREEN_USB_COMPOSITE To compile this driver as a module, choose M here: the module will be called usbtouchscreen. +config TOUCHSCREEN_MX25 + tristate "Freescale i.MX25 touchscreen input driver" + depends on MFD_MX25_TSADC + help + Enable support for touchscreen connected to your i.MX25. + config TOUCHSCREEN_MC13783 tristate "Freescale MC13783 touchscreen input driver" depends on MFD_MC13XXX diff --git a/drivers/input/touchscreen/Makefile b/drivers/input/touchscreen/Makefile index 0242fea2102a..bbb55a69c33c 100644 --- a/drivers/input/touchscreen/Makefile +++ b/drivers/input/touchscreen/Makefile @@ -41,6 +41,7 @@ obj-$(CONFIG_TOUCHSCREEN_INEXIO) += inexio.o obj-$(CONFIG_TOUCHSCREEN_INTEL_MID) += intel-mid-touch.o obj-$(CONFIG_TOUCHSCREEN_LPC32XX) += lpc32xx_ts.o obj-$(CONFIG_TOUCHSCREEN_MAX11801) += max11801_ts.o +obj-$(CONFIG_TOUCHSCREEN_MX25) += fsl-imx25-tcq.o obj-$(CONFIG_TOUCHSCREEN_MC13783) += mc13783_ts.o obj-$(CONFIG_TOUCHSCREEN_MCS5000) += mcs5000_ts.o obj-$(CONFIG_TOUCHSCREEN_MIGOR) += migor_ts.o diff --git a/drivers/input/touchscreen/fsl-imx25-tcq.c b/drivers/input/touchscreen/fsl-imx25-tcq.c new file mode 100644 index 000000000000..2eb3bd00d56c --- /dev/null +++ b/drivers/input/touchscreen/fsl-imx25-tcq.c @@ -0,0 +1,587 @@ +/* + * Copyright 2014 Markus Pargmann, Pengutronix <mpa@xxxxxxxxxxxxxx> + * Based on driver from 2011: + * Juergen Beisert, Pengutronix <kernel@xxxxxxxxxxxxxx> + * + * The code contained herein is licensed under the GNU General Public + * License. You may obtain a copy of the GNU General Public License + * Version 2 or later at the following locations: + * + * http://www.opensource.org/licenses/gpl-license.html + * http://www.gnu.org/copyleft/gpl.html + * + * This is the driver for the imx25 TCQ (Touchscreen Conversion Queue) + * connected to the imx25 ADC. + */ + +#include <linux/clk.h> +#include <linux/input.h> +#include <linux/interrupt.h> +#include <linux/mfd/imx25-tsadc.h> +#include <linux/module.h> +#include <linux/of.h> +#include <linux/platform_device.h> +#include <linux/regmap.h> + +static const char mx25_tcq_name[] = "mx25-tcq"; + +enum mx25_tcq_mode { + MX25_TS_4WIRE, +}; + +struct mx25_tcq_priv { + struct regmap *regs; + struct regmap *core_regs; + struct input_dev *idev; + enum mx25_tcq_mode mode; + unsigned int pen_threshold; + unsigned int sample_count; + unsigned int expected_samples; + unsigned int pen_debounce; + unsigned int settling_time; + struct clk *clk; + int irq; +}; + +static struct regmap_config mx25_tcq_regconfig = { + .fast_io = true, + .max_register = 0x5c, + .reg_bits = 32, + .val_bits = 32, + .reg_stride = 4, +}; + +static struct of_device_id mx25_tcq_ids[] = { + { .compatible = "fsl,imx25-tcq", }, + { /* Sentinel */ } +}; + +#define TSC_4WIRE_PRE_INDEX 0 +#define TSC_4WIRE_X_INDEX 1 +#define TSC_4WIRE_Y_INDEX 2 +#define TSC_4WIRE_POST_INDEX 3 +#define TSC_4WIRE_LEAVE 4 + +#define MX25_TSC_DEF_THRESHOLD 80 +#define TSC_MAX_SAMPLES 16 + +#define MX25_TSC_REPEAT_WAIT 14 + +enum mx25_adc_configurations { + MX25_CFG_PRECHARGE = 0, + MX25_CFG_TOUCH_DETECT, + MX25_CFG_X_MEASUREMENT, + MX25_CFG_Y_MEASUREMENT, +}; + +#define MX25_PRECHARGE_VALUE (\ + MX25_ADCQ_CFG_YPLL_OFF | \ + MX25_ADCQ_CFG_XNUR_OFF | \ + MX25_ADCQ_CFG_XPUL_HIGH | \ + MX25_ADCQ_CFG_REFP_INT | \ + MX25_ADCQ_CFG_IN_XP | \ + MX25_ADCQ_CFG_REFN_NGND2 | \ + MX25_ADCQ_CFG_IGS) + +#define MX25_TOUCH_DETECT_VALUE (\ + MX25_ADCQ_CFG_YNLR | \ + MX25_ADCQ_CFG_YPLL_OFF | \ + MX25_ADCQ_CFG_XNUR_OFF | \ + MX25_ADCQ_CFG_XPUL_OFF | \ + MX25_ADCQ_CFG_REFP_INT | \ + MX25_ADCQ_CFG_IN_XP | \ + MX25_ADCQ_CFG_REFN_NGND2 | \ + MX25_ADCQ_CFG_PENIACK) + +static void imx25_setup_queue_cfgs(struct mx25_tcq_priv *priv, + unsigned int settling_time) +{ + u32 precharge_cfg = + MX25_PRECHARGE_VALUE | + MX25_ADCQ_CFG_SETTLING_TIME(settling_time); + u32 touch_detect_cfg = + MX25_TOUCH_DETECT_VALUE | + MX25_ADCQ_CFG_NOS(1) | + MX25_ADCQ_CFG_SETTLING_TIME(settling_time); + + regmap_write(priv->core_regs, MX25_TSC_TICR, precharge_cfg); + + /* PRECHARGE */ + regmap_write(priv->regs, MX25_ADCQ_CFG(MX25_CFG_PRECHARGE), + precharge_cfg); + + /* TOUCH_DETECT */ + regmap_write(priv->regs, MX25_ADCQ_CFG(MX25_CFG_TOUCH_DETECT), + touch_detect_cfg); + + /* X Measurement */ + regmap_write(priv->regs, MX25_ADCQ_CFG(MX25_CFG_X_MEASUREMENT), + MX25_ADCQ_CFG_YPLL_OFF | + MX25_ADCQ_CFG_XNUR_LOW | + MX25_ADCQ_CFG_XPUL_HIGH | + MX25_ADCQ_CFG_REFP_XP | + MX25_ADCQ_CFG_IN_YP | + MX25_ADCQ_CFG_REFN_XN | + MX25_ADCQ_CFG_NOS(priv->sample_count) | + MX25_ADCQ_CFG_SETTLING_TIME(settling_time)); + + /* Y Measurement */ + regmap_write(priv->regs, MX25_ADCQ_CFG(MX25_CFG_Y_MEASUREMENT), + MX25_ADCQ_CFG_YNLR | + MX25_ADCQ_CFG_YPLL_HIGH | + MX25_ADCQ_CFG_XNUR_OFF | + MX25_ADCQ_CFG_XPUL_OFF | + MX25_ADCQ_CFG_REFP_YP | + MX25_ADCQ_CFG_IN_XP | + MX25_ADCQ_CFG_REFN_YN | + MX25_ADCQ_CFG_NOS(priv->sample_count) | + MX25_ADCQ_CFG_SETTLING_TIME(settling_time)); + + /* Enable the touch detection right now */ + regmap_write(priv->core_regs, MX25_TSC_TICR, touch_detect_cfg | + MX25_ADCQ_CFG_IGS); +} + +static int imx25_setup_queue_4wire(struct mx25_tcq_priv *priv, + unsigned settling_time, int *items) +{ + imx25_setup_queue_cfgs(priv, settling_time); + + /* Setup the conversion queue */ + regmap_write(priv->regs, MX25_ADCQ_ITEM_7_0, + MX25_ADCQ_ITEM(0, MX25_CFG_PRECHARGE) | + MX25_ADCQ_ITEM(1, MX25_CFG_TOUCH_DETECT) | + MX25_ADCQ_ITEM(2, MX25_CFG_X_MEASUREMENT) | + MX25_ADCQ_ITEM(3, MX25_CFG_Y_MEASUREMENT) | + MX25_ADCQ_ITEM(4, MX25_CFG_PRECHARGE) | + MX25_ADCQ_ITEM(5, MX25_CFG_TOUCH_DETECT)); + + /* We measure X/Y with 'sample_count' number of samples and execute a + * touch detection twice, with 1 sample each */ + priv->expected_samples = priv->sample_count * 2 + 2; + *items = 6; + + return 0; +} + +static void mx25_tcq_disable_touch_irq(struct mx25_tcq_priv *priv) +{ + regmap_update_bits(priv->regs, MX25_ADCQ_CR, MX25_ADCQ_CR_PDMSK, + MX25_ADCQ_CR_PDMSK); +} + +static void mx25_tcq_enable_touch_irq(struct mx25_tcq_priv *priv) +{ + regmap_update_bits(priv->regs, MX25_ADCQ_CR, MX25_ADCQ_CR_PDMSK, 0); +} + +static void mx25_tcq_disable_fifo_irq(struct mx25_tcq_priv *priv) +{ + regmap_update_bits(priv->regs, MX25_ADCQ_MR, MX25_ADCQ_MR_FDRY_IRQ, + MX25_ADCQ_MR_FDRY_IRQ); +} + +static void mx25_tcq_enable_fifo_irq(struct mx25_tcq_priv *priv) +{ + regmap_update_bits(priv->regs, MX25_ADCQ_MR, MX25_ADCQ_MR_FDRY_IRQ, 0); +} + +static void mx25_tcq_force_queue_start(struct mx25_tcq_priv *priv) +{ + regmap_update_bits(priv->regs, MX25_ADCQ_CR, + MX25_ADCQ_CR_FQS, + MX25_ADCQ_CR_FQS); +} + +static void mx25_tcq_force_queue_stop(struct mx25_tcq_priv *priv) +{ + regmap_update_bits(priv->regs, MX25_ADCQ_CR, + MX25_ADCQ_CR_FQS, 0); +} + +static void mx25_tcq_fifo_reset(struct mx25_tcq_priv *priv) +{ + u32 tcqcr; + + regmap_read(priv->regs, MX25_ADCQ_CR, &tcqcr); + regmap_update_bits(priv->regs, MX25_ADCQ_CR, MX25_ADCQ_CR_FRST, + MX25_ADCQ_CR_FRST); + regmap_update_bits(priv->regs, MX25_ADCQ_CR, MX25_ADCQ_CR_FRST, 0); + regmap_write(priv->regs, MX25_ADCQ_CR, tcqcr); +} + +static void mx25_tcq_re_enable_touch_detection(struct mx25_tcq_priv *priv) +{ + /* stop the queue from looping */ + mx25_tcq_force_queue_stop(priv); + + /* for a clean touch detection, preload the X plane */ + regmap_write(priv->core_regs, MX25_TSC_TICR, MX25_PRECHARGE_VALUE); + + /* waste some time now to pre-load the X plate to high voltage */ + mx25_tcq_fifo_reset(priv); + + /* re-enable the detection right now */ + regmap_write(priv->core_regs, MX25_TSC_TICR, + MX25_TOUCH_DETECT_VALUE | MX25_ADCQ_CFG_IGS); + + regmap_update_bits(priv->regs, MX25_ADCQ_SR, MX25_ADCQ_SR_PD, + MX25_ADCQ_SR_PD); + + /* enable the pen down event to be a source for the interrupt */ + regmap_update_bits(priv->regs, MX25_ADCQ_MR, MX25_ADCQ_MR_PD_IRQ, 0); + + /* lets fire the next IRQ if someone touches the touchscreen */ + mx25_tcq_enable_touch_irq(priv); +} + +static int mx25_tcq_create_event_for_4wire(struct mx25_tcq_priv *priv, + u32 *sample_buf, + unsigned int samples) +{ + unsigned int x_pos = 0; + unsigned int y_pos = 0; + unsigned int touch_pre = 0; + unsigned int touch_post = 0; + unsigned int i; + int ret = 0; + + for (i = 0; i < samples; i++) { + unsigned int index = MX25_ADCQ_FIFO_ID(sample_buf[i]); + unsigned int val = MX25_ADCQ_FIFO_DATA(sample_buf[i]); + + switch (index) { + case 1: + touch_pre = val; + break; + case 2: + x_pos = val; + break; + case 3: + y_pos = val; + break; + case 5: + touch_post = val; + break; + default: + ret = -EINVAL; + break; + } + } + + if (ret == 0 && samples != 0) { + /* + * only if both touch measures are below a threshold, + * the position is valid + */ + if (touch_pre < priv->pen_threshold && + touch_post < priv->pen_threshold) { + /* valid samples, generate a report */ + x_pos /= priv->sample_count; + y_pos /= priv->sample_count; + input_report_abs(priv->idev, ABS_X, x_pos); + input_report_abs(priv->idev, ABS_Y, y_pos); + input_report_key(priv->idev, BTN_TOUCH, 1); + input_sync(priv->idev); + + /* get next sample */ + mx25_tcq_enable_fifo_irq(priv); + } else if (touch_pre >= priv->pen_threshold && + touch_post >= priv->pen_threshold) { + /* + * if both samples are invalid, + * generate a release report + */ + input_report_key(priv->idev, BTN_TOUCH, 0); + input_sync(priv->idev); + mx25_tcq_re_enable_touch_detection(priv); + } else { + /* + * if only one of both touch measurements are + * below the threshold, still some bouncing + * happens. Take additional samples in this + * case to be sure + */ + mx25_tcq_enable_fifo_irq(priv); + } + } + + return ret; +} + +static irqreturn_t mx25_tcq_irq_thread(int irq, void *dev_id) +{ + struct mx25_tcq_priv *priv = dev_id; + u32 sample_buf[TSC_MAX_SAMPLES]; + unsigned int samples = 0; + + /* read all samples */ + while (1) { + u32 stats; + + regmap_read(priv->regs, MX25_ADCQ_SR, &stats); + if (stats & MX25_ADCQ_SR_EMPT) + break; + + if (samples < TSC_MAX_SAMPLES) { + regmap_read(priv->regs, MX25_ADCQ_FIFO, + &sample_buf[samples]); + ++samples; + } else { + u32 discarded; + /* discard samples */ + regmap_read(priv->regs, MX25_ADCQ_FIFO, &discarded); + } + } + + mx25_tcq_create_event_for_4wire(priv, sample_buf, samples); + + return IRQ_HANDLED; +} + +static irqreturn_t mx25_tcq_irq(int irq, void *dev_id) +{ + struct mx25_tcq_priv *priv = dev_id; + u32 stat; + int ret = IRQ_HANDLED; + + regmap_read(priv->regs, MX25_ADCQ_SR, &stat); + + if (stat & (MX25_ADCQ_SR_FRR | MX25_ADCQ_SR_FUR | MX25_ADCQ_SR_FOR)) + mx25_tcq_fifo_reset(priv); + + if (stat & MX25_ADCQ_SR_PD) { + mx25_tcq_disable_touch_irq(priv); + mx25_tcq_force_queue_start(priv); + mx25_tcq_enable_fifo_irq(priv); + } + + if (stat & MX25_ADCQ_SR_FDRY) { + mx25_tcq_disable_fifo_irq(priv); + ret = IRQ_WAKE_THREAD; + } + + regmap_update_bits(priv->regs, MX25_ADCQ_SR, MX25_ADCQ_SR_FRR | + MX25_ADCQ_SR_FUR | MX25_ADCQ_SR_FOR | + MX25_ADCQ_SR_PD | MX25_ADCQ_SR_EOQ, + MX25_ADCQ_SR_FRR | MX25_ADCQ_SR_FUR | + MX25_ADCQ_SR_FOR | MX25_ADCQ_SR_PD | + MX25_ADCQ_SR_EOQ); + + return ret; +} + +/* configure the statemachine for a 4-wire touchscreen */ +static int mx25_tcq_init(struct mx25_tcq_priv *priv) +{ + u32 tgcr; + unsigned int ipg_div; + unsigned int adc_period; + unsigned int debounce_cnt; + unsigned int settling_time; + int itemct; + int ret; + + regmap_read(priv->core_regs, MX25_TSC_TGCR, &tgcr); + ipg_div = max_t(unsigned int, 4, MX25_TGCR_GET_ADCCLK(tgcr)); + adc_period = clk_get_rate(priv->clk) / (ipg_div * 2 + 2); + debounce_cnt = DIV_ROUND_UP(priv->pen_debounce, adc_period * 8) - 1; + settling_time = DIV_ROUND_UP(priv->settling_time, adc_period); + + /* Reset */ + regmap_write(priv->regs, MX25_ADCQ_CR, + MX25_ADCQ_CR_QRST | MX25_ADCQ_CR_FRST); + regmap_update_bits(priv->regs, MX25_ADCQ_CR, + MX25_ADCQ_CR_QRST | MX25_ADCQ_CR_FRST, 0); + + /* up to 128 * 8 ADC clocks are possible */ + if (debounce_cnt > 127) + debounce_cnt = 127; + + ret = imx25_setup_queue_4wire(priv, settling_time, &itemct); + if (ret) + return ret; + + regmap_update_bits(priv->regs, MX25_ADCQ_CR, + MX25_ADCQ_CR_LITEMID_MASK | MX25_ADCQ_CR_WMRK_MASK, + MX25_ADCQ_CR_LITEMID(itemct - 1) | + MX25_ADCQ_CR_WMRK(priv->expected_samples - 1)); + + /* setup debounce count */ + regmap_update_bits(priv->core_regs, MX25_TSC_TGCR, + MX25_TGCR_PDBTIME_MASK, + MX25_TGCR_PDBTIME(debounce_cnt)); + + /* enable debounce */ + regmap_update_bits(priv->core_regs, MX25_TSC_TGCR, MX25_TGCR_PDBEN, + MX25_TGCR_PDBEN); + regmap_update_bits(priv->core_regs, MX25_TSC_TGCR, MX25_TGCR_PDEN, + MX25_TGCR_PDEN); + + /* enable the engine on demand */ + regmap_update_bits(priv->regs, MX25_ADCQ_CR, MX25_ADCQ_CR_QSM_MASK, + MX25_ADCQ_CR_QSM_FQS); + + /* Enable repeat and repeat wait */ + regmap_update_bits(priv->regs, MX25_ADCQ_CR, + MX25_ADCQ_CR_RPT | MX25_ADCQ_CR_RWAIT_MASK, + MX25_ADCQ_CR_RPT | + MX25_ADCQ_CR_RWAIT(MX25_TSC_REPEAT_WAIT)); + + mx25_tcq_re_enable_touch_detection(priv); + + return 0; +} + +static int mx25_tcq_parse_dt(struct platform_device *pdev, + struct mx25_tcq_priv *priv) +{ + struct device_node *np = pdev->dev.of_node; + u32 wires; + int ret; + + /* Setup defaults */ + priv->pen_threshold = 500; + priv->sample_count = 3; + priv->pen_debounce = 1000000; + priv->settling_time = 250000; + + ret = of_property_read_u32(np, "fsl,wires", &wires); + if (ret) { + dev_err(&pdev->dev, "Failed to find fsl,wires properties\n"); + return ret; + } + + if (wires == 4) { + priv->mode = MX25_TS_4WIRE; + } else { + dev_err(&pdev->dev, "%u-wire mode not supported\n", wires); + return -EINVAL; + } + + /* These are optional, we don't care about the return values */ + of_property_read_u32(np, "fsl,pen-threshold", &priv->pen_threshold); + of_property_read_u32(np, "fsl,settling-time", &priv->settling_time); + of_property_read_u32(np, "fsl,pen-debounce", &priv->pen_debounce); + + return 0; +} + +static int mx25_tcq_probe(struct platform_device *pdev) +{ + struct device *dev = &pdev->dev; + struct input_dev *idev; + struct mx25_tcq_priv *priv; + struct mx25_tsadc *tsadc = dev_get_drvdata(pdev->dev.parent); + struct resource *res; + void __iomem *mem; + int ret; + + priv = devm_kzalloc(dev, sizeof(*priv), GFP_KERNEL); + if (!priv) + return -ENOMEM; + + res = platform_get_resource(pdev, IORESOURCE_MEM, 0); + mem = devm_ioremap_resource(dev, res); + if (!mem) + return -ENOMEM; + + ret = mx25_tcq_parse_dt(pdev, priv); + if (ret) + return ret; + + priv->regs = devm_regmap_init_mmio(dev, mem, &mx25_tcq_regconfig); + if (IS_ERR(priv->regs)) { + dev_err(dev, "Failed to initialize regmap\n"); + return PTR_ERR(priv->regs); + } + + priv->irq = platform_get_irq(pdev, 0); + if (priv->irq <= 0) { + dev_err(dev, "Failed to get IRQ\n"); + return priv->irq; + } + + idev = devm_input_allocate_device(dev); + if (!idev) { + dev_err(dev, "Failed to allocate input device\n"); + return -ENOMEM; + } + + idev->name = mx25_tcq_name; + idev->evbit[0] = BIT_MASK(EV_KEY) | BIT_MASK(EV_ABS); + idev->keybit[BIT_WORD(BTN_TOUCH)] = BIT_MASK(BTN_TOUCH); + input_set_abs_params(idev, ABS_X, 0, 0xfff, 0, 0); + input_set_abs_params(idev, ABS_Y, 0, 0xfff, 0, 0); + + idev->id.bustype = BUS_HOST; + + ret = input_register_device(idev); + if (ret) { + dev_err(dev, "Failed to register input device\n"); + return ret; + } + + priv->idev = idev; + + priv->core_regs = tsadc->regs; + if (!priv->core_regs) + return -EINVAL; + + priv->clk = tsadc->clk; + if (!priv->clk) + return -EINVAL; + + ret = clk_prepare_enable(priv->clk); + if (ret) { + dev_err(dev, "Failed to enable ipg clock\n"); + return ret; + } + + ret = request_threaded_irq(priv->irq, mx25_tcq_irq, mx25_tcq_irq_thread, + IRQF_ONESHOT, pdev->name, priv); + if (ret) { + dev_err(dev, "Failed requesting IRQ\n"); + goto err_clk_unprepare; + } + + ret = mx25_tcq_init(priv); + if (ret) { + dev_err(dev, "Failed to init tcq\n"); + goto error_free_irq; + } + + platform_set_drvdata(pdev, priv); + + return 0; + +error_free_irq: + free_irq(priv->irq, priv); +err_clk_unprepare: + clk_disable_unprepare(priv->clk); + return ret; +} + +static int mx25_tcq_remove(struct platform_device *pdev) +{ + struct mx25_tcq_priv *priv = platform_get_drvdata(pdev); + + free_irq(priv->irq, priv); + clk_disable_unprepare(priv->clk); + + return 0; +} + +static struct platform_driver mx25_tcq_driver = { + .driver = { + .name = "mx25-tcq", + .of_match_table = mx25_tcq_ids, + }, + .probe = mx25_tcq_probe, + .remove = mx25_tcq_remove, +}; +module_platform_driver(mx25_tcq_driver); + +MODULE_DESCRIPTION("TS input driver for Freescale mx25"); +MODULE_AUTHOR("Markus Pargmann <mpa@xxxxxxxxxxxxxx>"); +MODULE_LICENSE("GPL v2"); -- 2.1.4 -- To unsubscribe from this list: send the line "unsubscribe linux-iio" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
