RE: [EXTERNAL] Re: [PATCH v10] ASoC: tas2781: Add tas2781 driver

[Ding, Shenghao]

Hi Both
I wrote a test code to verify the be32_to_cpu & be32_to_cpup,
static int __init lkm_init(void)
{
	char test_buf[]={0x12, 0x34, 0xab, 0xbc, 0x56, 0x78, 0xef};
	unsigned int *k, p, q;
	int i;

	printk("Hello, Shanghai!\n");

	for (i = 0; i < 4; i ++) {
		k = (unsigned int *)&test_buf[i];
		p = be32_to_cpup((__be32 *)k);
		q = be32_to_cpu(test_buf[i]);
		printk("%d: *k = 0x%08x p = 0x%08x q = 0x%08x %ld\n",
			i, *k, p, q, sizeof(unsigned int));
	}
	return 0;
}
The output is:
[ 9109.722548] Hello, Shanghai!
[ 9109.726287] 0: *k = 0xbcab3412 p = 0x1234abbc q = 0x12000000 4
[ 9109.727665] 1: *k = 0x56bcab34 p = 0x34abbc56 q = 0x34000000 4
[ 9109.728553] 2: *k = 0x7856bcab p = 0xabbc5678 q = 0xabffffff 4
[ 9109.729308] 3: *k = 0xef7856bc p = 0xbc5678ef q = 0xbcffffff 4
Apparently, be32_to_cpup's output is what I expected.
Looking forward to your comments. Thanks.

BR
Shenghao Ding
-----Original Message-----
From: Christophe JAILLET <christophe.jaillet@xxxxxxxxxx> 
Sent: Saturday, April 1, 2023 4:41 AM
To: Ding, Shenghao <shenghao-ding@xxxxxx>; Amadeusz Slawinski <amadeuszx.slawinski@xxxxxxxxxxxxxxx>; Shenghao Ding <13916275206@xxxxxxx>; broonie@xxxxxxxxxx; lgirdwood@xxxxxxxxx; perex@xxxxxxxx; pierre-louis.bossart@xxxxxxxxxxxxxxx
Cc: Lu, Kevin <kevin-lu@xxxxxx>; alsa-devel@xxxxxxxxxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx; Xu, Baojun <x1077012@xxxxxx>; Gupta, Peeyush <peeyush@xxxxxx>; Navada Kanyana, Mukund <navada@xxxxxx>
Subject: [EXTERNAL] 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@xxxxxxxxxxxxxxx>
> Sent: Thursday, March 30, 2023 7:54 PM
> To: Shenghao Ding <13916275206@xxxxxxx>; broonie@xxxxxxxxxx; 
> lgirdwood@xxxxxxxxx; perex@xxxxxxxx; 
> pierre-louis.bossart@xxxxxxxxxxxxxxx
> Cc: Lu, Kevin <kevin-lu@xxxxxx>; Ding, Shenghao 
> <shenghao-ding@xxxxxx>; alsa-devel@xxxxxxxxxxxxxxxx; 
> linux-kernel@xxxxxxxxxxxxxxx; Xu, Baojun <x1077012@xxxxxx>; Gupta, 
> Peeyush <peeyush@xxxxxx>; Navada Kanyana, Mukund <navada@xxxxxx>
> 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@xxxxxxx>
>>
>> ---
>> 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