This patch adds three new sysfs files: frequency, frequency_min and frequency_max which allows the user to view or change the bus frequency on a per bus level.
This is required for the case where multiple busses have the same adapter driver in which case a module parameter does not allow controlling the bus speed individually (e.g. USB I2C adapters). Signed-off-by: Octavian Purdila <[email protected]> --- Documentation/ABI/testing/sysfs-bus-i2c | 30 +++++++++++ drivers/i2c/i2c-core.c | 90 +++++++++++++++++++++++++++++++++ include/linux/i2c.h | 16 ++++++ 3 files changed, 136 insertions(+) diff --git a/Documentation/ABI/testing/sysfs-bus-i2c b/Documentation/ABI/testing/sysfs-bus-i2c index 8075585..70af81f 100644 --- a/Documentation/ABI/testing/sysfs-bus-i2c +++ b/Documentation/ABI/testing/sysfs-bus-i2c @@ -43,3 +43,33 @@ Contact: [email protected] Description: An i2c device attached to bus X that is enumerated via ACPI. Y is the ACPI device name and its format is "%s". + +What: /sys/bus/i2c/devices/i2c-X/frequency +KernelVersion: 3.19 +Contact: [email protected] +Description: + The current bus frequency for bus X. Can be updated if + the bus supports it. The unit is HZ and format is + "%d\n". + If the bus does not support changing the frequency + then this entry will be read-only. + If the bus does not support showing the frequency than + this entry will not be visible. + When updating the bus frequency that value must be in + the range defined by bus_frequency_min and + bus_frequency_max otherwise writing to this entry will + fail with -EINVAL. + The bus may not support all of the frequencies in the + min-max range and may round the frequency to the + closest supported one. The user must read the entry + after writing it to retrieve the actual set frequency. + +What: /sys/bus/i2c/devices/i2c-X/frequency_min +What: /sys/bus/i2c/devices/i2c-X/frequency_max +KernelVersion: 3.19 +Contact: [email protected] +Description: + Minimum and maximum frequencies for bus X. The unit is + HZ and format is "%d\n". + If the bus does not support changing the frequency + these entries will not be visible. diff --git a/drivers/i2c/i2c-core.c b/drivers/i2c/i2c-core.c index 632057a..27c29eb 100644 --- a/drivers/i2c/i2c-core.c +++ b/drivers/i2c/i2c-core.c @@ -940,15 +940,97 @@ static DEVICE_ATTR(new_device, S_IWUSR, NULL, i2c_sysfs_new_device); static DEVICE_ATTR_IGNORE_LOCKDEP(delete_device, S_IWUSR, NULL, i2c_sysfs_delete_device); +static ssize_t +i2c_sysfs_freq_show(struct device *dev, struct device_attribute *attr, + char *buf) +{ + struct i2c_adapter *adap = to_i2c_adapter(dev); + + return snprintf(buf, PAGE_SIZE, "%d\n", adap->freq); +} + +static ssize_t +i2c_sysfs_freq_store(struct device *dev, struct device_attribute *attr, + const char *buf, size_t count) +{ + struct i2c_adapter *adap = to_i2c_adapter(dev); + unsigned int freq; + int ret; + + if (kstrtouint(buf, 0, &freq) || freq < adap->min_freq || + freq > adap->max_freq) + return -EINVAL; + + i2c_lock_adapter(adap); + ret = adap->set_freq(adap, &freq); + i2c_unlock_adapter(adap); + + if (ret) + return ret; + + adap->freq = freq; + + return count; +} + +static DEVICE_ATTR(frequency, S_IRUGO, i2c_sysfs_freq_show, + i2c_sysfs_freq_store); + +static ssize_t frequency_min_show(struct device *dev, + struct device_attribute *attr, char *buf) +{ + struct i2c_adapter *adap = to_i2c_adapter(dev); + + return snprintf(buf, PAGE_SIZE, "%d\n", adap->min_freq); +} + +static DEVICE_ATTR_RO(frequency_min); + +static ssize_t frequency_max_show(struct device *dev, + struct device_attribute *attr, char *buf) +{ + struct i2c_adapter *adap = to_i2c_adapter(dev); + + return snprintf(buf, PAGE_SIZE, "%d\n", adap->max_freq); +} + +static DEVICE_ATTR_RO(frequency_max); + +static umode_t i2c_adapter_visible_attr(struct kobject *kobj, + struct attribute *attr, int idx) +{ + struct device *dev = container_of(kobj, struct device, kobj); + struct i2c_adapter *adap = to_i2c_adapter(dev); + umode_t mode = attr->mode; + + if (attr == &dev_attr_frequency_min.attr) + return adap->min_freq ? mode : 0; + + if (attr == &dev_attr_frequency_max.attr) + return adap->max_freq ? mode : 0; + + if (attr == &dev_attr_frequency.attr) { + if (adap->set_freq) + mode |= S_IWUSR; + return adap->freq ? mode : 0; + } + + return mode; +} + static struct attribute *i2c_adapter_attrs[] = { &dev_attr_name.attr, &dev_attr_new_device.attr, &dev_attr_delete_device.attr, + &dev_attr_frequency.attr, + &dev_attr_frequency_min.attr, + &dev_attr_frequency_max.attr, NULL }; static struct attribute_group i2c_adapter_attr_group = { .attrs = i2c_adapter_attrs, + .is_visible = i2c_adapter_visible_attr, }; static const struct attribute_group *i2c_adapter_attr_groups[] = { @@ -1262,6 +1344,14 @@ int i2c_add_adapter(struct i2c_adapter *adapter) struct device *dev = &adapter->dev; int id; + if (adapter->set_freq) { + if (!adapter->freq || !adapter->min_freq || !adapter->max_freq) + return -EINVAL; + } else { + if (adapter->min_freq || adapter->max_freq) + return -EINVAL; + } + if (dev->of_node) { id = of_alias_get_id(dev->of_node, "i2c"); if (id >= 0) { diff --git a/include/linux/i2c.h b/include/linux/i2c.h index 36041e2..5d893f5 100644 --- a/include/linux/i2c.h +++ b/include/linux/i2c.h @@ -431,6 +431,17 @@ int i2c_generic_scl_recovery(struct i2c_adapter *adap); * usb->interface->dev, platform_device->dev etc.) * @name: name of this i2c bus * @bus_recovery_info: see struct i2c_bus_recovery_info. Optional. + * @set_freq: set the bus frequency (in HZ) and returns the actual set + * value. Since not all the frequencies in the min - max interval + * may be valid the driver may round the frequency to the closest + * supported one. Optional but must be set if min_freq or + * max_freq is set. + * @min_freq: minimum bus frequency. Optional but must be set if + * set_freq is set. + * @max_freq: maximum bus frequency. Optional but must be set if + * set_freq is set. + * @freq: initial bus frequency. Optional but must be set if set_freq + * is set. */ struct i2c_adapter { struct module *owner; @@ -438,6 +449,11 @@ struct i2c_adapter { const struct i2c_algorithm *algo; /* the algorithm to access the bus */ void *algo_data; + unsigned int freq; + unsigned int min_freq; + unsigned int max_freq; + int (*set_freq)(struct i2c_adapter *a, unsigned int *freq); + /* data fields that are valid for all devices */ struct rt_mutex bus_lock; -- 1.9.1 -- To unsubscribe from this list: send the line "unsubscribe linux-api" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html
