On 02/03/2025 05:27, Jonathan Cameron wrote:
On Wed, 26 Feb 2025 08:39:11 +0200
Matti Vaittinen <mazziesaccount@xxxxxxxxx> wrote:
On 26/02/2025 02:09, David Lechner wrote:
On 2/24/25 12:34 PM, Matti Vaittinen wrote:
The ti-ads7924 driver ignores the device-tree ADC channel specification
and always exposes all 4 channels to users whether they are present in
the device-tree or not. Additionally, the "reg" values in the channel
nodes are ignored, although an error is printed if they are out of range.
Register only the channels described in the device-tree, and use the reg
property as a channel ID.
Signed-off-by: Matti Vaittinen <mazziesaccount@xxxxxxxxx>
---
Revision history:
v3 => v4:
- Adapt to 'drop diff-channel support' changes to ADC-helpers
- select ADC helpers in the Kconfig
v2 => v3: New patch
Please note that this is potentially breaking existing users if they
have wrong values in the device-tree. I believe the device-tree should
ideally be respected, and if it says device X has only one channel, then
we should believe it and not register 4. Well, we don't live in the
ideal world, so even though I believe this is TheRightThingToDo - it may
cause havoc because correct device-tree has not been required from the
day 1. So, please review and test and apply at your own risk :)
The DT bindings on this one are a little weird. Usually, if we don't
use any extra properties from adc.yaml, we leave out the channels. In
this case it does seem kind of like the original intention was to work
like you are suggesting, but hard to say since the driver wasn't actually
implemented that way. I would be more inclined to actually not make the
breaking change here and instead relax the bindings to make channel nodes
optional and just have the driver ignore the channel nodes by dropping
the ads7924_get_channels_config() function completely. This would make
the driver simpler instead of more complex like this patch does.
I have no strong opinion on this. I see this driver says 'Supported' in
MAINTAINERS. Maybe Hugo is able to provide some insight?
This seems to be ABI breakage. Never something we can take if there is
a significant chance of anyone noticing. Here it looks like risk
is too high.
Ok. I'll just drop this patch then. Thanks David & Jonathan :)
Yours,
-- Matti
