On Tue, Jan 27, 2015 at 11:52:34AM +0100, Hans de Goede wrote: > Hi, > > On 27-01-15 10:49, Priit Laes wrote: > > > >On Tue, 2015-01-27 at 10:18 +0100, Maxime Ripard wrote: > >>Hi, > >> > >>On Mon, Jan 26, 2015 at 06:58:32PM +0200, Priit Laes wrote: > >>>--- > >> > >>Like Hans was pointing out, commit log and signed-off-by please > >> > >>> .../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@xxxxxxxxx> > >>>+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. > > > >[...] > > > > > >> > >>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. Maxime -- Maxime Ripard, Free Electrons Embedded Linux, Kernel and Android engineering http://free-electrons.com
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