ASoC: stm32: sai: Use of_device_get_match_data() to simplify code

Retrieve of match data, it's better and cleaner to use
'of_device_get_match_data' over 'of_match_device'.

Signed-off-by: Tang Bin <tangbin@cmss.chinamobile.com>
---
 sound/soc/stm/stm32_sai_sub.c | 6 ++----
 1 file changed, 2 insertions(+), 4 deletions(-)

Hello Tang,

Thanks for the patch. Unfortunately this patch introduces a regression.

In the SAI driver of_device_id struct the data is a simple enum cast to 
void* pointer.
static const struct of_device_id stm32_sai_sub_ids[] = {
	  .data = (void *)STM_SAI_A_ID},

This data is an ID which can be set to 0x0.
Here we have no way to know to discriminate between an error returned by 
of_device_get_match_data() or a data id set to 0x0.

The current patch requires a change in the driver.
Either changing STM_SAI_x_ID enums, or replacing data by a struct.
For instance:
struct stm32_sai_comp_data {
	unsigned int id;
}
struct stm32_sai_comp_data stm32_sai_comp_data_a = {
	.id = STM_SAI_A_ID;
}
struct of_device_id stm32_sai_sub_ids[] = {
	.data = &stm32_sai_comp_data_a},
}

Regards
Olivier

On 5/19/22 14:42, Tang Bin wrote:
> Retrieve of match data, it's better and cleaner to use
> 'of_device_get_match_data' over 'of_match_device'.
> 
> Signed-off-by: Tang Bin <tangbin@cmss.chinamobile.com>
> ---
>   sound/soc/stm/stm32_sai_sub.c | 6 ++----
>   1 file changed, 2 insertions(+), 4 deletions(-)
> 
> diff --git a/sound/soc/stm/stm32_sai_sub.c b/sound/soc/stm/stm32_sai_sub.c
> index dd636af81..d300605a2 100644
> --- a/sound/soc/stm/stm32_sai_sub.c
> +++ b/sound/soc/stm/stm32_sai_sub.c
> @@ -1500,7 +1500,6 @@ static int stm32_sai_sub_parse_of(struct platform_device *pdev,
>   static int stm32_sai_sub_probe(struct platform_device *pdev)
>   {
>   	struct stm32_sai_sub_data *sai;
> -	const struct of_device_id *of_id;
>   	const struct snd_dmaengine_pcm_config *conf = &stm32_sai_pcm_config;
>   	int ret;
>   
> @@ -1508,10 +1507,9 @@ static int stm32_sai_sub_probe(struct platform_device *pdev)
>   	if (!sai)
>   		return -ENOMEM;
>   
> -	of_id = of_match_device(stm32_sai_sub_ids, &pdev->dev);
> -	if (!of_id)
> +	sai->id = (uintptr_t)of_device_get_match_data(&pdev->dev);
> +	if (!sai->id)
>   		return -EINVAL;
> -	sai->id = (uintptr_t)of_id->data;
>   
>   	sai->pdev = pdev;
>   	mutex_init(&sai->ctrl_lock);

On Mon, May 23, 2022 at 03:28:48PM +0200, Olivier MOYSAN wrote:

> The current patch requires a change in the driver.
> Either changing STM_SAI_x_ID enums, or replacing data by a struct.
> For instance:
> struct stm32_sai_comp_data {
> 	unsigned int id;
> }
> struct stm32_sai_comp_data stm32_sai_comp_data_a = {
> 	.id = STM_SAI_A_ID;
> }
> struct of_device_id stm32_sai_sub_ids[] = {
> 	.data = &stm32_sai_comp_data_a},
> }

Either approach works for me (or a revert for that matter).

Hi Mark & Olivier：

On 2022/5/24 2:57, Mark Brown wrote:
> On Mon, May 23, 2022 at 03:28:48PM +0200, Olivier MOYSAN wrote:
>
>> The current patch requires a change in the driver.
>> Either changing STM_SAI_x_ID enums, or replacing data by a struct.
>> For instance:
>> struct stm32_sai_comp_data {
>> 	unsigned int id;
>> }
>> struct stm32_sai_comp_data stm32_sai_comp_data_a = {
>> 	.id = STM_SAI_A_ID;
>> }
>> struct of_device_id stm32_sai_sub_ids[] = {
>> 	.data = &stm32_sai_comp_data_a},
>> }
> Either approach works for me (or a revert for that matter).

     Thanks for your advice, I was thoughtless.

     I think change the date of STM_SAI_x_ID maybe simple. But if we 
don't change the id,

what about add a "#define" like the line 47:

#define STM_SAI_IS_SUB(x) ((x)->id == STM_SAI_A_ID || (x)->id == 
STM_SAI_B_ID)

then in the judgement, wu use:

     sai->id = (uintptr_t)of_device_get_match_data(&pdev->dev);

     if (!STM_SAI_IS_SUB(sai))

             return -EINVAL;


if you think that's ok, I will send patch v2 for you .

Thanks

Tang Bin

Hi Tang,

On 5/24/22 03:44, tangbin wrote:
> Hi Mark & Olivier：
> 
> On 2022/5/24 2:57, Mark Brown wrote:
>> On Mon, May 23, 2022 at 03:28:48PM +0200, Olivier MOYSAN wrote:
>>
>>> The current patch requires a change in the driver.
>>> Either changing STM_SAI_x_ID enums, or replacing data by a struct.
>>> For instance:
>>> struct stm32_sai_comp_data {
>>>     unsigned int id;
>>> }
>>> struct stm32_sai_comp_data stm32_sai_comp_data_a = {
>>>     .id = STM_SAI_A_ID;
>>> }
>>> struct of_device_id stm32_sai_sub_ids[] = {
>>>     .data = &stm32_sai_comp_data_a},
>>> }
>> Either approach works for me (or a revert for that matter).
> 
>      Thanks for your advice, I was thoughtless.
> 
>      I think change the date of STM_SAI_x_ID maybe simple. But if we 
> don't change the id,
> 
> what about add a "#define" like the line 47:
> 
> #define STM_SAI_IS_SUB(x) ((x)->id == STM_SAI_A_ID || (x)->id == 
> STM_SAI_B_ID)
> 
> then in the judgement, wu use:
> 
>      sai->id = (uintptr_t)of_device_get_match_data(&pdev->dev);
> 
>      if (!STM_SAI_IS_SUB(sai))
> 
>              return -EINVAL;
> 
> 
> if you think that's ok, I will send patch v2 for you .
> 

If we allow null value in STM_SAI_IS_SUB(sai) check, we can miss real 
NULL pointer error from of_device_get_match_data().

The simplest way is to change STM_SAI_x_ID enums I think.
But honnestly, I feel more comfortable to let the driver unchanged.

BRs
Olivier

> Thanks
> 
> Tang Bin
> 
>