Re: [PATCH 2/4] dt-bindings: input: edt-ft5x06 - add no-regmap-bulk-read property

Re: [PATCH 2/4] dt-bindings: input: edt-ft5x06 - add no-regmap-bulk-read property

[Conor Dooley]

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On Thu, Jul 23, 2026 at 06:27:09PM +0700, Alexandre Hamamdjian via B4 Relay wrote:
> From: Alexandre Hamamdjian <azkali.limited@gmail.com>
> 
> Document an optional boolean property for boards whose i2c controller
> cannot reliably sustain the multi-byte block read of a full touch frame.
> When set, the driver reads the frame one register at a time instead of in
> a single bulk transfer.
> 
> Signed-off-by: Alexandre Hamamdjian <azkali.limited@gmail.com>
> ---
>  .../devicetree/bindings/input/touchscreen/edt-ft5x06.yaml         | 8 ++++++++
>  1 file changed, 8 insertions(+)
> 
> diff --git a/Documentation/devicetree/bindings/input/touchscreen/edt-ft5x06.yaml b/Documentation/devicetree/bindings/input/touchscreen/edt-ft5x06.yaml
> index 68b2f1601654..0d8310a290ea 100644
> --- a/Documentation/devicetree/bindings/input/touchscreen/edt-ft5x06.yaml
> +++ b/Documentation/devicetree/bindings/input/touchscreen/edt-ft5x06.yaml
> @@ -111,6 +111,14 @@ properties:
>  
>    interrupt-controller: true
>  
> +  no-regmap-bulk-read:

"regmap" is a linux software construct, nothing to do with this
touchscreen or hardware at all for that matter - it's i2c bulk reads you
cannot do.

> +    type: boolean
> +    description:
> +      Set this when the i2c controller the touch controller is attached to

Problems with your controller should be dealt with at the controller
level, not in the device node because the device doesn't have a problem,
the controller does. I think "i2c_adapter_quirks" is the knob used for
this.
This kind of property seems to have come up the other day in a similar context:
https://lore.kernel.org/all/20260722-regmap-single-read-v1-0-aaaf31591669@linux.dev/
The regmap maintainer there rejected a device level property in favour
of discovering this from the controller.

pwbot: rejected

Cheers,
Conor.

> +      cannot reliably sustain the multi-byte block read of a full touch
> +      frame and aborts long transfers. The driver then reads the touch
> +      frame one register at a time instead of in a single bulk transfer.
> +
>  unevaluatedProperties: false
>  
>  required:
> 
> -- 
> 2.55.0
> 
> 

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Re: [PATCH 1/4] Input: edt-ft5x06 - ignore contacts with an out-of-range slot id

[Dmitry Torokhov]

On Thu, Jul 23, 2026 at 11:40:59AM +0000, sashiko-bot@kernel.org wrote:
> Thank you for your contribution! Sashiko AI review found 2 potential issue(s) to consider:
> 
> Pre-existing issues:
> - [High] Unbalanced `disable_irq()` calls when suspending and resuming in factory mode lead to a permanently disabled touchscreen.

This is obviously not caused by your series but might be real, need to
check...

> - [High] Stack-allocated buffers are passed to `regmap_bulk_read()` and `i2c_transfer()`, which can cause memory corruption or panics if the underlying I2C host controller driver uses DMA.

Sashiko hallucinates here. I added I2C prompt to teach it that I2C is
generally safe wrt on-stack buffers, but I am not sure if it will trace
it to regmap.

Thanks.

-- 
Dmitry