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

[Christophe JAILLET]

Le 05/04/2023 à 13:21, Ding, Shenghao a écrit :
> 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.

Hi,

thanks for the clarification and code sample.
You are right.

I had in mind that something like: be32_to_cpu((__be32 *)data);
would make it. (thanks to the cast)

But because of the need of "&" and "[offset]", it would just make the 
code unnecessarily complex.

I think that your approach is better.

CJ