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SubjectRe: [PATCH 3/3] ASoC: aw88395: drop undocumented and unused sound-channel property
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On 05/09/2023 04:46, wangweidong.a@awinic.com wrote:
> Thank you very much for the proposed patch, but I have some
> questions that I would like to discuss with you
>
> On Mon, Sep 04, 2023 at 12:53 PM +0200, Krzysztof Kozlowski wrote:
>> The Devicetree sound-channel property was never accepted and is not
>> allowed by bindings. It is not used by any upstream user, thus
>> considering that it was never documented, should be dropped.
>
> This node property is intended for use with multiple PA, to
> load different configurations for different PA.
> Can I add this sound-channel in the "awinic,aw88395.yaml" file?

Maybe?

>
>> Even though it does not look like from the diff, the property is not
>> actually used by the driver, because once set, it is read only in loops
>> depending on ddt_num (prof_hdr->ddt_num, cfg_hdr->ddt_num). The
>> variable ddt_num is never set and is always 0, so the loops do not have
>> any iteration. Dropping sound-channel and ddt_num-related loops allows
>> to drop empty functions which in turn drop quite a lot of code. This
>> entire code was not possible to execute.
>
> The ddt_num variable is not always 0, this variable is defined
> in the configuration file. The "prof_hdr" variable is assigned by
> the "cfg_hdr" variable. The "cfg_hdr" variable is assigned by "aw_cfg"
> aw_cfg is the data obtained through request_firmware.The specific
> process is as follows:
>
> request_firmware ---> cont->data ---> aw_cfg->data --> cfg_hdr --> prof_hdr

Hm. So you load user-space provided file and assign it directly, without
any validation (aw88395_dev_load_acf_check() checks only for magic), to
a kernel structure. Sounds bullet-proof. Why using known kernel
interfaces, better to implement some conf-file-parsing.


Best regards,
Krzysztof

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