linux-kernel - Re: [PATCH v10] ASoC: tas2781: Add tas2781 driver

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Message-ID: <458d7c2f-bcee-9ec3-e955-9661a06a3349@wanadoo.fr>
Date:   Fri, 31 Mar 2023 22:41:22 +0200
From:   Christophe JAILLET <christophe.jaillet@...adoo.fr>
To:     "Ding, Shenghao" <shenghao-ding@...com>,
        Amadeusz Slawinski <amadeuszx.slawinski@...ux.intel.com>,
        Shenghao Ding <13916275206@....com>,
        "broonie@...nel.org" <broonie@...nel.org>,
        "lgirdwood@...il.com" <lgirdwood@...il.com>,
        "perex@...ex.cz" <perex@...ex.cz>,
        "pierre-louis.bossart@...ux.intel.com" 
        <pierre-louis.bossart@...ux.intel.com>
Cc:     "Lu, Kevin" <kevin-lu@...com>,
        "alsa-devel@...a-project.org" <alsa-devel@...a-project.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "Xu, Baojun" <x1077012@...com>, "Gupta, Peeyush" <peeyush@...com>,
        "Navada Kanyana, Mukund" <navada@...com>
Subject: Re: [PATCH v10] ASoC: tas2781: Add tas2781 driver

Le 31/03/2023 à 04:19, Ding, Shenghao a écrit :
> Hi Amadeusz Sławiński
> Thanks for your comment.
> Answer inline.
> 
> -----Original Message-----
> From: Amadeusz Sławiński <amadeuszx.slawinski@...ux.intel.com>
> Sent: Thursday, March 30, 2023 7:54 PM
> To: Shenghao Ding <13916275206@....com>; broonie@...nel.org; lgirdwood@...il.com; perex@...ex.cz; pierre-louis.bossart@...ux.intel.com
> Cc: Lu, Kevin <kevin-lu@...com>; Ding, Shenghao <shenghao-ding@...com>; alsa-devel@...a-project.org; linux-kernel@...r.kernel.org; Xu, Baojun <x1077012@...com>; Gupta, Peeyush <peeyush@...com>; Navada Kanyana, Mukund <navada@...com>
> Subject: [EXTERNAL] Re: [PATCH v10] ASoC: tas2781: Add tas2781 driver
> 
> On 3/29/2023 12:01 PM, Shenghao Ding wrote:
>> Create tas2781 driver.
>>
>> Signed-off-by: Shenghao Ding <13916275206@....com>
>>
>> ---
>> Changes in v10:
>>    - using be16_to_cpu and be32_to_cpu instead of SMS_HTONS and SMS_HTONL
>>    - optimize and reduce the boundary checks
>>    - Add comments on some kmemdup instead of kzalloc+memcpy
>>    Changes to be committed:
>> 	modified:   sound/soc/codecs/Kconfig
>> 	modified:   sound/soc/codecs/Makefile
>> 	new file:   sound/soc/codecs/tas2781-dsp.c
>> 	new file:   sound/soc/codecs/tas2781-dsp.h
>> 	new file:   sound/soc/codecs/tas2781-i2c.c
>> 	new file:   sound/soc/codecs/tas2781.h
>> ---
> 
> ...
> 
>> +
>> +static int fw_parse_block_data_kernel(struct tasdevice_fw *tas_fmw,
>> +	struct tasdev_blk *block, const struct firmware *fmw, int offset) {
>> +	const unsigned char *data = fmw->data;
>> +
>> +	if (offset + 16 > fmw->size) {
>> +		dev_err(tas_fmw->dev, "%s: File Size error\n", __func__);
>> +		offset = -EINVAL;
>> +		goto out;
>> +	}
>> +	block->type = be32_to_cpup((__be32 *)&data[offset]);
> 
> Wouldn't just be32_to_cpu(data[offset]) work instead of be32_to_cpup?
> Same in other cases.
> [DING] data[] is a char array, the code will convert data[offset], data[offset + 1],
> data[offset + 2] and data[offset + 3] into host instead of data[offset] only.
> 

Not sure to follow you.
Isn't it the purpose of be32_to_cpu() to take a 32 bits word, in other 
words 4 x 8 bits char, and swap what if needed (little endian arch)?

It ends to __swab32() ([1] for the "constant" implementation)


be32_to_cpup(&p) ends to __swab32(*p), which really looks to the same as 
be32_to_cpu(p).

Can you elaborate more?

CJ


[1]: 
https://elixir.bootlin.com/linux/v6.3-rc3/source/include/uapi/linux/swab.h#L18