Hello,

On Wed, Aug 24, 2016 at 02:45:17PM +0530, Vignesh R wrote:

On Wednesday 24 August 2016 02:05 PM, Daniel Mack wrote:

quoted

On 08/24/2016 09:58 AM, Vignesh R wrote:

quoted

This series adds support for rotary-switch on AM335x-ICE that is
connected to TI PCA9536 I2C GPIO expander.
First patch adds new generic driver to read status of group of GPIO
lines and report the value as an input event. The second patch adds DT
entries for the same.

v2: https://lkml.org/lkml/2016/8/23/111
v1: https://lkml.org/lkml/2016/8/12/7

Is there a reason why the rotary-encoder driver cannot handle this?
Commit 7dde4e74744 ("Input: rotary-encoder - support more than 2 gpios
as input") added support for that mode AFAIU.

Rotary encoder driver handles incremental encoders only and does not
support absolute encoders. The rotary switch on am335x-ice is different
from the incremental encoders in the
sense that GPIO line status directly reflect the position(number)
pointed by the dial of the encoder. So, there is no need to count steps
or know the direction of rotation as it does not matter.

I'd still prefer to expand drivers/input/misc/rotary_encoder.c to handle
this. Yes, there is no reason to count steps or determine the direction
of a rotation in this case, but still there is much code to share and
IMHO it's ok that a driver that handles several types of similar devices
does too much for some special cases.

I did try to enhance rotary-encoder driver to support absolute
encoder[1] but the comment there was to write new driver that simply
translates gpio-encoded value into ABS* event. Indeed, the new driver
looks more simple and can handle more such hardwares.

Which type of hardware can be handled by your driver that the generic
rotary encoder cannot? I guess it's just a matter of a (simple) patch?

Best regards
Uwe

[1] https://lkml.org/lkml/2016/5/19/98

-- 
Pengutronix e.K.                           | Uwe Kleine-König            |
Industrial Linux Solutions                 | http://www.pengutronix.de/  |
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