Messages in this thread | | | Date | Tue, 27 Jan 2015 11:52:34 +0100 | From | Hans de Goede <> | Subject | Re: [linux-sunxi] Re: [PATCH] arm: sunxi: input: RFC: Add sysfs voltage for sun4i-lradc driver |
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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@plaes.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. > > [...] > > >> >> 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.
Regards,
Hans
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