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Date: Thu, 9 Oct 2014 23:07:15 +0300
From: Octavian Purdila <octavian.purdila@...el.com>
To: wsa@...-dreams.de
Cc: johan@...nel.org, linux-i2c@...r.kernel.org,
linux-api@...r.kernel.org, linux-kernel@...r.kernel.org,
Octavian Purdila <octavian.purdila@...el.com>
Subject: [RFC PATCH 3/3] i2c: show and change bus frequency via sysfs
This patch adds two new sysfs files, bus_frequency and
bus_supported_frequencies which allows the user to view or change the
bus frequency on a per bus level.
This is required for e.g. USB I2C buses where we can have multiple
device plugged in a system and where a module parameter does not allow
controlling the bus speed individually.
Signed-off-by: Octavian Purdila <octavian.purdila@...el.com>
---
Documentation/ABI/testing/sysfs-bus-i2c | 24 ++++++++++
drivers/i2c/i2c-core.c | 77 +++++++++++++++++++++++++++++++++
include/linux/i2c.h | 10 +++++
3 files changed, 111 insertions(+)
diff --git a/Documentation/ABI/testing/sysfs-bus-i2c b/Documentation/ABI/testing/sysfs-bus-i2c
index 22c621a..058ac68 100644
--- a/Documentation/ABI/testing/sysfs-bus-i2c
+++ b/Documentation/ABI/testing/sysfs-bus-i2c
@@ -43,3 +43,27 @@ Contact: linux-i2c@...r.kernel.org
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/bus_frequency
+KernelVersion: 3.19
+Contact: linux-i2c@...r.kernel.org
+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 showing/changing the
+ frequency then reading/writting to this entry will
+ fail with -EOPNOTSUPP.
+ When updating the bus frequency that value must be one
+ of the values in bus_supported_frequencies otherwise
+ writting will fail with -EINVAL.
+
+What: /sys/bus/i2c/devices/i2c-X/bus_supported_frequencies
+KernelVersion: 3.19
+Contact: linux-i2c@...r.kernel.org
+Description:
+ Supported frequencies for bus X. The unit is HZ and
+ format is "%d %d %d ... %d\n".
+ If the bus does not support showing/changing the
+ frequency then reading to this entry will fail with
+ -EOPNOTSUPP.
diff --git a/drivers/i2c/i2c-core.c b/drivers/i2c/i2c-core.c
index 632057a..32b918a 100644
--- a/drivers/i2c/i2c-core.c
+++ b/drivers/i2c/i2c-core.c
@@ -940,10 +940,87 @@ 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);
+
+ if (!adap->freq)
+ return -EOPNOTSUPP;
+
+ 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;
+ int i;
+
+ if (!adap->set_freq)
+ return -EOPNOTSUPP;
+
+ if (kstrtouint(buf, 0, &freq))
+ return -EINVAL;
+
+ if (freq == 0)
+ return -EINVAL;
+
+ for (i = 0; i < I2C_MAX_FREQS && adap->supported_freqs[i]; i++)
+ if (adap->supported_freqs[i] >= freq)
+ break;
+
+ if (adap->supported_freqs[i] != 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(bus_frequency, S_IWUSR | S_IRUGO, i2c_sysfs_freq_show,
+ i2c_sysfs_freq_store);
+
+
+static ssize_t
+i2c_sysfs_supp_freqs_show(struct device *dev, struct device_attribute *attr,
+ char *buf)
+{
+ struct i2c_adapter *adap = to_i2c_adapter(dev);
+ ssize_t count = 0;
+ int i;
+
+ if (!adap->supported_freqs[0])
+ return -EOPNOTSUPP;
+
+ for (i = 0; i < I2C_MAX_FREQS && adap->supported_freqs[i]; i++)
+ count += snprintf(buf + count, PAGE_SIZE - count, "%d ",
+ adap->supported_freqs[i]);
+ buf[count - 1] = '\n';
+
+ return count;
+}
+
+static DEVICE_ATTR(bus_supported_frequencies, S_IRUGO,
+ i2c_sysfs_supp_freqs_show, NULL);
+
static struct attribute *i2c_adapter_attrs[] = {
&dev_attr_name.attr,
&dev_attr_new_device.attr,
&dev_attr_delete_device.attr,
+ &dev_attr_bus_frequency.attr,
+ &dev_attr_bus_supported_frequencies.attr,
NULL
};
diff --git a/include/linux/i2c.h b/include/linux/i2c.h
index 36041e2..e410637 100644
--- a/include/linux/i2c.h
+++ b/include/linux/i2c.h
@@ -418,6 +418,8 @@ int i2c_recover_bus(struct i2c_adapter *adap);
int i2c_generic_gpio_recovery(struct i2c_adapter *adap);
int i2c_generic_scl_recovery(struct i2c_adapter *adap);
+#define I2C_MAX_FREQS 16
+
/**
* struct i2c_adapter - represents an I2C physical bus
*
@@ -431,6 +433,10 @@ 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.
+ * @supported_freqs: supported bus frequencies (in HZ). Must be sorted
+ * in ascending order. Optional.
+ * @freq: initial bus frequency. Optional.
+ * @set_bus_freq: set the bus frequency (in HZ). Optional.
*/
struct i2c_adapter {
struct module *owner;
@@ -438,6 +444,10 @@ struct i2c_adapter {
const struct i2c_algorithm *algo; /* the algorithm to access the bus */
void *algo_data;
+ unsigned int supported_freqs[I2C_MAX_FREQS];
+ unsigned int 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
--
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