Messages in this thread | | | Date | Wed, 5 Apr 2023 13:35:34 +0200 | Subject | Re: [EXTERNAL] Re: [PATCH v10] ASoC: tas2781: Add tas2781 driver | From | Amadeusz Sławiński <> |
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On 4/5/2023 1:21 PM, Ding, Shenghao wrote: > 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. >
It makes sense, as array access reads 8 bit value, you would need to access value using pointer instead. So instead of doing be32_to_cpu(test_buf[i]) you would need to do be32_to_cpu(*(test_buf + i)) if I didn't mess the pointer magic ;)
And then I'm not sure which is better, be32_to_cpup or be32_to_cpu.
> BR > Shenghao Ding > -----Original Message----- > From: Christophe JAILLET <christophe.jaillet@wanadoo.fr> > Sent: Saturday, April 1, 2023 4:41 AM > To: Ding, Shenghao <shenghao-ding@ti.com>; Amadeusz Slawinski <amadeuszx.slawinski@linux.intel.com>; Shenghao Ding <13916275206@139.com>; broonie@kernel.org; lgirdwood@gmail.com; perex@perex.cz; pierre-louis.bossart@linux.intel.com > Cc: Lu, Kevin <kevin-lu@ti.com>; alsa-devel@alsa-project.org; linux-kernel@vger.kernel.org; Xu, Baojun <x1077012@ti.com>; Gupta, Peeyush <peeyush@ti.com>; Navada Kanyana, Mukund <navada@ti.com> > 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@linux.intel.com> >> Sent: Thursday, March 30, 2023 7:54 PM >> To: Shenghao Ding <13916275206@139.com>; broonie@kernel.org; >> lgirdwood@gmail.com; perex@perex.cz; >> pierre-louis.bossart@linux.intel.com >> Cc: Lu, Kevin <kevin-lu@ti.com>; Ding, Shenghao >> <shenghao-ding@ti.com>; alsa-devel@alsa-project.org; >> linux-kernel@vger.kernel.org; Xu, Baojun <x1077012@ti.com>; Gupta, >> Peeyush <peeyush@ti.com>; Navada Kanyana, Mukund <navada@ti.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@139.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 >
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