c - How does kernel code knows which spi bus is using? -
i modified device tree file , enable spi using 4 gpio pins, support pinmux , switch gpio spi function. in linux kernel code, how code know spi bus/pins used? example, find linux kernel driver: max1111.c, drives spi adc chip. checked code, , don't find spi bus/pins specified.
i paste max1111.c below.
/* * max1111.c - +2.7v, low-power, multichannel, serial 8-bit adcs * * based on arch/arm/mach-pxa/corgi_ssp.c * * copyright (c) 2004-2005 richard purdie * * copyright (c) 2008 marvell international ltd. * eric miao <eric.miao@marvell.com> * * program free software; can redistribute and/or modify * under terms of gnu general public license version 2 * publishhed free software foundation. */ #include <linux/module.h> #include <linux/kernel.h> #include <linux/init.h> #include <linux/err.h> #include <linux/hwmon.h> #include <linux/hwmon-sysfs.h> #include <linux/spi/spi.h> #include <linux/slab.h> enum chips { max1110, max1111, max1112, max1113 }; #define max1111_tx_buf_size 1 #define max1111_rx_buf_size 2 /* max1111 commands */ #define max1111_ctrl_pd0 (1u << 0) #define max1111_ctrl_pd1 (1u << 1) #define max1111_ctrl_sgl (1u << 2) #define max1111_ctrl_uni (1u << 3) #define max1110_ctrl_sel_sh (4) #define max1111_ctrl_sel_sh (5) /* note: bit 4 ignored */ #define max1111_ctrl_str (1u << 7) struct max1111_data { struct spi_device *spi; struct device *hwmon_dev; struct spi_message msg; struct spi_transfer xfer[2]; uint8_t tx_buf[max1111_tx_buf_size]; uint8_t rx_buf[max1111_rx_buf_size]; struct mutex drvdata_lock; /* protect msg, xfer , buffers multiple access */ int sel_sh; int lsb; }; static int max1111_read(struct device *dev, int channel) { struct max1111_data *data = dev_get_drvdata(dev); uint8_t v1, v2; int err; /* writing drvdata struct not thread safe, wait on mutex */ mutex_lock(&data->drvdata_lock); data->tx_buf[0] = (channel << data->sel_sh) | max1111_ctrl_pd0 | max1111_ctrl_pd1 | max1111_ctrl_sgl | max1111_ctrl_uni | max1111_ctrl_str; err = spi_sync(data->spi, &data->msg); if (err < 0) { dev_err(dev, "spi_sync failed %d\n", err); mutex_unlock(&data->drvdata_lock); return err; } v1 = data->rx_buf[0]; v2 = data->rx_buf[1]; mutex_unlock(&data->drvdata_lock); if ((v1 & 0xc0) || (v2 & 0x3f)) return -einval; return (v1 << 2) | (v2 >> 6); } #ifdef config_sharpsl_pm static struct max1111_data *the_max1111; int max1111_read_channel(int channel) { return max1111_read(&the_max1111->spi->dev, channel); } export_symbol(max1111_read_channel); #endif /* * note: spi devices not have default 'name' attribute, * used hwmon applications distinguish between * different devices, explicitly add name attribute here. */ static ssize_t show_name(struct device *dev, struct device_attribute *attr, char *buf) { return sprintf(buf, "%s\n", to_spi_device(dev)->modalias); } static ssize_t show_adc(struct device *dev, struct device_attribute *attr, char *buf) { struct max1111_data *data = dev_get_drvdata(dev); int channel = to_sensor_dev_attr(attr)->index; int ret; ret = max1111_read(dev, channel); if (ret < 0) return ret; /* * assume reference voltage 2.048v or 4.096v, 8-bit * sample. lsb weight 8mv or 16mv depending on chip type. */ return sprintf(buf, "%d\n", ret * data->lsb); } #define max1111_adc_attr(_id) \ sensor_device_attr(in##_id##_input, s_irugo, show_adc, null, _id) static device_attr(name, s_irugo, show_name, null); static max1111_adc_attr(0); static max1111_adc_attr(1); static max1111_adc_attr(2); static max1111_adc_attr(3); static max1111_adc_attr(4); static max1111_adc_attr(5); static max1111_adc_attr(6); static max1111_adc_attr(7); static struct attribute *max1111_attributes[] = { &dev_attr_name.attr, &sensor_dev_attr_in0_input.dev_attr.attr, &sensor_dev_attr_in1_input.dev_attr.attr, &sensor_dev_attr_in2_input.dev_attr.attr, &sensor_dev_attr_in3_input.dev_attr.attr, null, }; static const struct attribute_group max1111_attr_group = { .attrs = max1111_attributes, }; static struct attribute *max1110_attributes[] = { &sensor_dev_attr_in4_input.dev_attr.attr, &sensor_dev_attr_in5_input.dev_attr.attr, &sensor_dev_attr_in6_input.dev_attr.attr, &sensor_dev_attr_in7_input.dev_attr.attr, null, }; static const struct attribute_group max1110_attr_group = { .attrs = max1110_attributes, }; static int setup_transfer(struct max1111_data *data) { struct spi_message *m; struct spi_transfer *x; m = &data->msg; x = &data->xfer[0]; spi_message_init(m); x->tx_buf = &data->tx_buf[0]; x->len = max1111_tx_buf_size; spi_message_add_tail(x, m); x++; x->rx_buf = &data->rx_buf[0]; x->len = max1111_rx_buf_size; spi_message_add_tail(x, m); return 0; } static int max1111_probe(struct spi_device *spi) { enum chips chip = spi_get_device_id(spi)->driver_data; struct max1111_data *data; int err; spi->bits_per_word = 8; spi->mode = spi_mode_0; err = spi_setup(spi); if (err < 0) return err; data = devm_kzalloc(&spi->dev, sizeof(struct max1111_data), gfp_kernel); if (data == null) { dev_err(&spi->dev, "failed allocate memory\n"); return -enomem; } switch (chip) { case max1110: data->lsb = 8; data->sel_sh = max1110_ctrl_sel_sh; break; case max1111: data->lsb = 8; data->sel_sh = max1111_ctrl_sel_sh; break; case max1112: data->lsb = 16; data->sel_sh = max1110_ctrl_sel_sh; break; case max1113: data->lsb = 16; data->sel_sh = max1111_ctrl_sel_sh; break; } err = setup_transfer(data); if (err) return err; mutex_init(&data->drvdata_lock); data->spi = spi; spi_set_drvdata(spi, data); err = sysfs_create_group(&spi->dev.kobj, &max1111_attr_group); if (err) { dev_err(&spi->dev, "failed create attribute group\n"); return err; } if (chip == max1110 || chip == max1112) { err = sysfs_create_group(&spi->dev.kobj, &max1110_attr_group); if (err) { dev_err(&spi->dev, "failed create extended attribute group\n"); goto err_remove; } } data->hwmon_dev = hwmon_device_register(&spi->dev); if (is_err(data->hwmon_dev)) { dev_err(&spi->dev, "failed create hwmon device\n"); err = ptr_err(data->hwmon_dev); goto err_remove; } #ifdef config_sharpsl_pm the_max1111 = data; #endif return 0; err_remove: sysfs_remove_group(&spi->dev.kobj, &max1110_attr_group); sysfs_remove_group(&spi->dev.kobj, &max1111_attr_group); return err; } static int max1111_remove(struct spi_device *spi) { struct max1111_data *data = spi_get_drvdata(spi); hwmon_device_unregister(data->hwmon_dev); sysfs_remove_group(&spi->dev.kobj, &max1110_attr_group); sysfs_remove_group(&spi->dev.kobj, &max1111_attr_group); mutex_destroy(&data->drvdata_lock); return 0; } static const struct spi_device_id max1111_ids[] = { { "max1110", max1110 }, { "max1111", max1111 }, { "max1112", max1112 }, { "max1113", max1113 }, { }, }; module_device_table(spi, max1111_ids); static struct spi_driver max1111_driver = { .driver = { .name = "max1111", .owner = this_module, }, .id_table = max1111_ids, .probe = max1111_probe, .remove = max1111_remove, }; module_spi_driver(max1111_driver); module_author("eric miao <eric.miao@marvell.com>"); module_description("max1110/max1111/max1112/max1113 adc driver"); module_license("gpl");
spi device driver (max1111 in case) pointer underlying spi-controller (struct spi_device *spi) during probe stage (max1111_probe). driver should use send requests controller (using spi_sync, example). driver doesn't know pins spi-controller use.
what spi-controller passed spi device driver? spi device, should declared in dts-file inside spi-controller node. controller initialized spi-controller node passed device probe.
spi-controller can hardware (specific soc), or spi-gpio. in case of hardware spi, pins dedicated , specified in soc trm. in case of spi-gpio, gpio names specified inside dts-properties of spi-gpio. properties names are: gpio-sck, gpio-miso, gpio-mosi, num-chipselects , cs-gpios (list).
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