On Tue, Jan 27, 2015 at 08:44:47PM +0100, Maxime Ripard wrote:

On Tue, Jan 27, 2015 at 11:52:34AM +0100, Hans de Goede wrote:

quoted

Hi,

On 27-01-15 10:49, Priit Laes wrote:

quoted

On Tue, 2015-01-27 at 10:18 +0100, Maxime Ripard wrote:

quoted

Hi,

On Mon, Jan 26, 2015 at 06:58:32PM +0200, Priit Laes wrote:

quoted

---

Like Hans was pointing out, commit log and signed-off-by please

quoted

 .../ABI/testing/sysfs-driver-input-sun4i-lradc     |  4 ++
 drivers/input/keyboard/sun4i-lradc-keys.c          | 49
+++++++++++++++++-----
 2 files changed, 43 insertions(+), 10 deletions(-)
 create mode 100644 Documentation/ABI/testing/sysfs-driver-input-
sun4i-lradc

diff --git a/Documentation/ABI/testing/sysfs-driver-input-sun4i-

lradc b/Documentation/ABI/testing/sysfs-driver-input-sun4i-lradc
new file mode 100644
index 0000000..e4e6448

--- /dev/null
+++ b/Documentation/ABI/testing/sysfs-driver-input-sun4i-lradc

@@ -0,0 +1,4 @@
+What:          /sys/class/input/input(x)/device/voltage
+Date:          February 2015
+Contact:       Priit Laes <plaes-q/aMd4JkU83YtjvyW6yDsg@public.gmane.org>
+Description:   ADC output voltage in microvolts or 0 if device is

not opened.

Why is it returning 0 when "device is not opened" ? What does that
even mean? You can't read that file without opening it.

It means that something has to open the /dev/input/inputX device which
sets up the ADC before the voltage can be read from the sysfs file.

[...]

quoted

As I told you already, if you're going to expose this an ADC in the
end, the proper solution is to use the IIO framework, not adding a
custom sysfs file.

My intention was to expose just a simple debug output, so one can
press the buttons and read the voltages for devicetree keymap.

If anyone can suggest a simpler approach than current sysfs based one,
I would do it.

The android driver always uses 0.2V / 200mV steps, so what I do is
simply create a mapping with 200mV mapped to KEY_VOLUMEUP, 400mV mapped
to KEY_VOLUMEDOWN, etc. following the hardcoded android driver mapping:

https://github.com/linux-sunxi/linux-sunxi/blob/sunxi-3.4/drivers/input/keyboard/sun4i-keyboard.c#L136

Usually this will be correct in one go, after testing one can shuffle
key codes as needed (usually not needed) and/or remove unused entries.

With that said I do think that a sysfs file to see the actual voltages,
or a kernel parameter to printk them on keypress interrupt would be useful.

I guess the printk option would be better as it would show the actual
keypress value read, not some semi-random sample.

That wouldn't require that much code actually. Either using dev_dbg,
or debugfs like Dmitry was suggesting would be two nice solutions I
guess.

Given the stated purpose I'd say dev_dbg() and call it a day.

Thanks.

-- 
Dmitry