Re: [PATCH v4 10/13] iio: adc: ad4134: Support SPI 4-wire mode

[Marcelo Schmitt]

On 10/06, sashiko-bot@xxxxxxxxxx wrote:
...
> [Severity: Medium]
> If spi_setup() fails here, we return the error but st->spi->mode remains
> modified. On subsequent calls, cur_mode != SPI_MODE_0 will evaluate to false
> because the cached mode reflects the requested state.
> 
> Can this cause the driver to bypass spi_setup() on subsequent calls and
> attempt to communicate with the device while the SPI hardware remains
> incorrectly configured?

Seems to make sense. Will double check and fix if needed.

...
> [Severity: High]
> Does this cause a deadlock during device probe in NO_CS mode?
> 
> Here the driver acquires and permanently selects the SDO multiplexer via
> devm_mux_state_get_optional_selected(), which acquires the multiplexer's
> non-recursive semaphore.
> 
> Immediately after, probe calls ad4134_min_io_mode_setup(), which writes to
> device registers via regmap_update_bits(). This triggers the following call
> chain:
> 
> ad4134_min_io_mode_setup()
>   regmap_update_bits()
>     ad4134_reg_write()
>       ad4134_claim_reg_access()
> 
> ad4134_claim_reg_access() unconditionally calls mux_state_select(), which
> will attempt to acquire the exact same semaphore already held by the current
> task, causing a deadlock.
> 
> Furthermore, ad4134_release_reg_access() then unconditionally calls
> mux_state_deselect(), which would prematurely release the probe-acquired
> lock.

Seems plausible. Will double check and fix if needed.


Other LLM comments don't seem to apply either because they are related to debug
interface usage or marginal issues.