linux-kernel - Re: [PATCH 3/3] ASoC: aw88395: drop undocumented and unused sound-channel property

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Date:   Tue,  5 Sep 2023 15:13:56 +0800
From:   wangweidong.a@...nic.com
To:     krzysztof.kozlowski@...aro.org
Cc:     alsa-devel@...a-project.org, broonie@...nel.org,
        lgirdwood@...il.com, linux-kernel@...r.kernel.org, perex@...ex.cz,
        tiwai@...e.com, wangweidong.a@...nic.com, yijiangtao@...nic.com
Subject: Re: [PATCH 3/3] ASoC: aw88395: drop undocumented and unused sound-channel property

Thank you very much for your reply.

On 05/09/2023 15:05, krzysztof.kozlowski@...aro.org wrote:
> On 05/09/2023 04:46, wangweidong.a@...nic.com wrote:

>>> 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.

Could you please tell me what known kernel interfaces 
can be used to parse files? 
Thank you very much

Best regards,
Weidong Wang