Hi,
On Thu, Oct 22, 2020 at 02:22:51PM +0000, Barnabás Pőcze wrote:
Hi,
I think this looks a lot better than the first version, the issues around
suspend/resume are sorted out as far as I can see. However, I still have a couple
comments, mainly minor ones.
Thank you for reviewing this patch!
[...]
+/* polling mode */
+#define I2C_HID_POLLING_DISABLED 0
+#define I2C_HID_POLLING_GPIO_PIN 1
+#define I2C_HID_POLLING_INTERVAL_ACTIVE_US 4000
+#define I2C_HID_POLLING_INTERVAL_IDLE_MS 10
+
+static u8 polling_mode;
+module_param(polling_mode, byte, 0444);
+MODULE_PARM_DESC(polling_mode, "How to poll - 0 disabled; 1 based on GPIO pin's status");
+
Minor thing, but maybe the default value should be documented in the parameter
description?
+static unsigned int polling_interval_active_us = I2C_HID_POLLING_INTERVAL_ACTIVE_US;
+module_param(polling_interval_active_us, uint, 0644);
+MODULE_PARM_DESC(polling_interval_active_us,
+ "Poll every {polling_interval_active_us} us when the touchpad is active. Default to 4000 us");
+
+static unsigned int polling_interval_idle_ms = I2C_HID_POLLING_INTERVAL_IDLE_MS;
Since these two parameters are mostly read, I think the `__read_mostly`
attribute (linux/cache.h) is justified here.
+module_param(polling_interval_idle_ms, uint, 0644);
+MODULE_PARM_DESC(polling_interval_idle_ms,
+ "Poll every {polling_interval_idle_ms} ms when the touchpad is idle. Default to 10 ms");
This is minor stylistic thing; as far as I see, the prevalent pattern is to put
the default value at the end, in parenthesis:
E.g. "some parameter description (default=X)" or "... (default: X)" or something similar
Maybe __stringify() (linux/stringify.h) could be used here and for the previous
module parameter?
E.g. "... (default=" __stringify(I2C_HID_POLLING_INTERVAL_IDLE_MS) ")"
Thank you for the above three suggestions! Will be applied in v4.
[...]
+static int get_gpio_pin_state(struct irq_desc *irq_desc)
+{
+ struct gpio_chip *gc = irq_data_get_irq_chip_data(&irq_desc->irq_data);
+
+ return gc->get(gc, irq_desc->irq_data.hwirq);
+}
+
+static bool interrupt_line_active(struct i2c_client *client)
+{
+ unsigned long trigger_type = irq_get_trigger_type(client->irq);
Can the trigger type change? Because if not, then I think it'd be better to store
the value somewhere and not query it every time.
The irq trigger type is obtained from ACPI so I don't think it won't
change.
+ struct irq_desc *irq_desc = irq_to_desc(client->irq);
Same here.
Thank you for the reminding!
+ ssize_t status = get_gpio_pin_state(irq_desc);
`get_gpio_pin_state()` returns an `int`, so I am not sure why `ssize_t` is used here.
I used `ssize_t` because I found gpiolib-sysfs.c uses `ssize_t`
// drivers/gpio/gpiolib-sysfs.c
static ssize_t value_show(struct device *dev,
struct device_attribute *attr, char *buf)
{
struct gpiod_data *data = dev_get_drvdata(dev);
struct gpio_desc *desc = data->desc;
ssize_t status;
mutex_lock(&data->mutex);
status = gpiod_get_value_cansleep(desc);
...
return status;
}
According to the book Advanced Programming in the UNIX Environment by
W. Richard Stevens,
With the 1990 POSIX.1 standard, the primitive system data type
ssize_t was introduced to provide the signed return value...
So ssize_t is fairly common, for example, the read and write syscall
return a value of type ssize_t. But I haven't found out why ssize_t is
better int.
+
+ if (status < 0) {
+ dev_warn(&client->dev,
+ "Failed to get GPIO Interrupt line status for %s",
+ client->name);
I think it's possible that the kernel message buffer is flooded with these
messages, which is not optimal in my opinion.
Thank you! Replaced with dev_dbg in v4.
+ return false;
+ }
+ /*
+ * According to Windows Precsiontion Touchpad's specs
+ * https://docs.microsoft.com/en-us/windows-hardware/design/component-guidelines/windows-precision-touchpad-device-bus-connectivity,
+ * GPIO Interrupt Assertion Leve could be either ActiveLow or
+ * ActiveHigh.
+ */
+ if (trigger_type & IRQF_TRIGGER_LOW)
+ return !status;
+
+ return status;
+}
+
+static int i2c_hid_polling_thread(void *i2c_hid)
+{
+ struct i2c_hid *ihid = i2c_hid;
+ struct i2c_client *client = ihid->client;
+ unsigned int polling_interval_idle;
+
+ while (1) {
+ if (kthread_should_stop())
+ break;
I think this should be `while (!kthread_should_stop())`.
This simplifies the code. Thank you!
+
+ while (interrupt_line_active(client) &&
+ !test_bit(I2C_HID_READ_PENDING, &ihid->flags) &&
+ !kthread_should_stop()) {
+ i2c_hid_get_input(ihid);
+ usleep_range(polling_interval_active_us,
+ polling_interval_active_us + 100);
+ }
+ /*
+ * re-calculate polling_interval_idle
+ * so the module parameters polling_interval_idle_ms can be
+ * changed dynamically through sysfs as polling_interval_active_us
+ */
+ polling_interval_idle = polling_interval_idle_ms * 1000;
+ usleep_range(polling_interval_idle,
+ polling_interval_idle + 1000);
I don't quite understand why you use an extra variable here. I'm assuming
you want to "save" a multiplication? I believe the compiler will optimize it
to a single read, and single multiplication regardless whether you use a "temporary"
variable or not.
+ }
+
+ do_exit(0);
Looking at other examples, I don't think `do_exit()` is necessary.
According to the doc of kthread_create_on_node,
@threadfn() can either call do_exit() directly if it is a
* standalone thread for which no one will call kthread_stop(), or
* return when 'kthread_should_stop()' is true (which means
* kthread_stop() has been called).
do_exit is not necessary. Thank you for raising up this issue and
looking at other examples for me!
+ return 0;
+}
+
+static int i2c_hid_init_polling(struct i2c_hid *ihid)
+{
+ struct i2c_client *client = ihid->client;
+
+ if (!irq_get_trigger_type(client->irq)) {
+ dev_warn(&client->dev,
+ "Failed to get GPIO Interrupt Assertion Level, could not enable polling mode for %s",
+ client->name);
+ return -EINVAL;
+ }
+
+ ihid->polling_thread = kthread_create(i2c_hid_polling_thread, ihid,
+ "I2C HID polling thread");
+
+ if (!IS_ERR(ihid->polling_thread)) {
+ pr_info("I2C HID polling thread created");
+ wake_up_process(ihid->polling_thread);
+ return 0;
+ }
+
+ return PTR_ERR(ihid->polling_thread);
I would personally rewrite this parts as
```
if (IS_ERR(...)) {
dev_err(...);
return PTR_ERR(...);
}
....
return 0;
```
Thank you! This style is consistent with other functions in this file.
+}
[...]
Regards,
Barnabás Pőcze
--
Best regards,
Coiby
