Re: [PATCH] mfd: mxs-lradc: Pass mapped IRQs to child devices

[Dmitry Torokhov <dmitry.torokhov@gmail.com>]

On Sat, Oct 17, 2026 at 11:24:00PM -0300, Fabio Estevam wrote:
> The MFD resource tables store indices into the parent DT interrupts
> property. Since the MFD core is given neither an IRQ domain nor a base,
> however, it exposes those indices to child devices as though they were
> Linux IRQ numbers.
> 
> The touchscreen interrupt is at DT index 0 on both supported SoCs.
> platform_get_irq_byname() therefore rejects its child resource with:
> 
>  0 is an invalid IRQ number
> 
> On current kernels it also returns -EINVAL, preventing the touchscreen
> driver from probing.
> 
> The child drivers try to map their resource values afterwards with
> irq_of_parse_and_map(), but the touchscreen driver never reaches that
> call for index 0. More generally, translating the parent firmware's IRQ
> indices does not belong in the child drivers, where platform IRQ
> resources are expected to contain mapped Linux IRQs already.
> 
> Have the MFD parent copy each resource template and resolve its IRQ
> indices with platform_get_irq() before registering the child. The child
> drivers can then request the mapped IRQs directly. Use per-device copies
> so later instances and reprobes still start with the DT indices.
> 
> Apply the same fix to the ADC child, which uses the same IRQ mapping
> scheme.
> 
> Tested on an i.MX28 EVK. The mxs-lradc-ts driver now probes
> successfully, and its interrupt counters increase when the screen is
> touched.
> 
> Cc: stable@vger.kernel.org
> Fixes: a85a6c86c25b ("driver core: platform: Clarify that IRQ 0 is invalid")
> Closes: https://lore.kernel.org/linux-input/CAOMZO5CgTzo6GuXptD4mFTN=UsJJqpkixDW1Q64gqZGrij8+uQ@mail.gmail.com/
> Signed-off-by: Fabio Estevam <festevam@gmail.com>
> ---
> This is a long-standing bug that I reported in 2020:
> https://lore.kernel.org/linux-input/CAOMZO5CgTzo6GuXptD4mFTN=UsJJqpkixDW1Q64gqZGrij8+uQ@mail.gmail.com/
> 
> This patch touches MFD, IIO, and Input. Since the IRQ mapping is moved
> into the MFD parent, I suggest merging it through the MFD tree, with
> acks from the IIO and Input maintainers.

Acked-by: Dmitry Torokhov <dmitry.torokhov@gmail.com> # for input

Thanks.

-- 
Dmitry