linux-kernel - Re: [PATCH 2/2] staging: atomisp: use local variable to reduce the number of reference

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Date:   Thu, 30 Mar 2017 09:19:20 +0200
From:   walter harms <wharms@....de>
To:     Daeseok Youn <daeseok.youn@...il.com>
CC:     mchehab@...nel.org, gregkh@...uxfoundation.org,
        alan@...ux.intel.com, dan.carpenter@...cle.com,
        singhalsimran0@...il.com, linux-media@...r.kernel.org,
        devel@...verdev.osuosl.org, linux-kernel@...r.kernel.org,
        kernel-janitors@...r.kernel.org
Subject: Re: [PATCH 2/2] staging: atomisp: use local variable to reduce the
 number of reference



Am 30.03.2017 08:25, schrieb Daeseok Youn:
> Define new local variable to reduce the number of reference.
> The new local variable is added to save the addess of dfs
> and used in atomisp_freq_scaling() function.
> 
> Signed-off-by: Daeseok Youn <daeseok.youn@...il.com>
> ---
>  .../media/atomisp/pci/atomisp2/atomisp_cmd.c       | 37 ++++++++++++----------
>  1 file changed, 20 insertions(+), 17 deletions(-)
> 
> diff --git a/drivers/staging/media/atomisp/pci/atomisp2/atomisp_cmd.c b/drivers/staging/media/atomisp/pci/atomisp2/atomisp_cmd.c
> index eebfccd..d76a95c 100644
> --- a/drivers/staging/media/atomisp/pci/atomisp2/atomisp_cmd.c
> +++ b/drivers/staging/media/atomisp/pci/atomisp2/atomisp_cmd.c
> @@ -251,6 +251,7 @@ int atomisp_freq_scaling(struct atomisp_device *isp,
>  {
>  	/* FIXME! Only use subdev[0] status yet */
>  	struct atomisp_sub_device *asd = &isp->asd[0];
> +	const struct atomisp_dfs_config *dfs;
>  	unsigned int new_freq;
>  	struct atomisp_freq_scaling_rule curr_rules;
>  	int i, ret;
> @@ -268,20 +269,22 @@ int atomisp_freq_scaling(struct atomisp_device *isp,
>  	    ATOMISP_USE_YUVPP(asd))
>  		isp->dfs = &dfs_config_cht_soc;
>  
> -	if (isp->dfs->lowest_freq == 0 || isp->dfs->max_freq_at_vmin == 0 ||
> -	    isp->dfs->highest_freq == 0 || isp->dfs->dfs_table_size == 0 ||
> -	    !isp->dfs->dfs_table) {
> +	dfs = isp->dfs;
> +
> +	if (dfs->lowest_freq == 0 || dfs->max_freq_at_vmin == 0 ||
> +	    dfs->highest_freq == 0 || dfs->dfs_table_size == 0 ||
> +	    !dfs->dfs_table) {
>  		dev_err(isp->dev, "DFS configuration is invalid.\n");
>  		return -EINVAL;
>  	}
>  
>  	if (mode == ATOMISP_DFS_MODE_LOW) {
> -		new_freq = isp->dfs->lowest_freq;
> +		new_freq = dfs->lowest_freq;
>  		goto done;
>  	}
>  
>  	if (mode == ATOMISP_DFS_MODE_MAX) {
> -		new_freq = isp->dfs->highest_freq;
> +		new_freq = dfs->highest_freq;
>  		goto done;
>  	}
>  
> @@ -307,26 +310,26 @@ int atomisp_freq_scaling(struct atomisp_device *isp,
>  	}
>  
>  	/* search for the target frequency by looping freq rules*/
> -	for (i = 0; i < isp->dfs->dfs_table_size; i++) {
> -		if (curr_rules.width != isp->dfs->dfs_table[i].width &&
> -		    isp->dfs->dfs_table[i].width != ISP_FREQ_RULE_ANY)
> +	for (i = 0; i < dfs->dfs_table_size; i++) {
> +		if (curr_rules.width != dfs->dfs_table[i].width &&
> +		    dfs->dfs_table[i].width != ISP_FREQ_RULE_ANY)
>  			continue;
> -		if (curr_rules.height != isp->dfs->dfs_table[i].height &&
> -		    isp->dfs->dfs_table[i].height != ISP_FREQ_RULE_ANY)
> +		if (curr_rules.height != dfs->dfs_table[i].height &&
> +		    dfs->dfs_table[i].height != ISP_FREQ_RULE_ANY)
>  			continue;
> -		if (curr_rules.fps != isp->dfs->dfs_table[i].fps &&
> -		    isp->dfs->dfs_table[i].fps != ISP_FREQ_RULE_ANY)
> +		if (curr_rules.fps != dfs->dfs_table[i].fps &&
> +		    dfs->dfs_table[i].fps != ISP_FREQ_RULE_ANY)
>  			continue;
> -		if (curr_rules.run_mode != isp->dfs->dfs_table[i].run_mode &&
> -		    isp->dfs->dfs_table[i].run_mode != ISP_FREQ_RULE_ANY)
> +		if (curr_rules.run_mode != dfs->dfs_table[i].run_mode &&
> +		    dfs->dfs_table[i].run_mode != ISP_FREQ_RULE_ANY)
>  			continue;
>  		break;
>  	}

>  
> -	if (i == isp->dfs->dfs_table_size)
> -		new_freq = isp->dfs->max_freq_at_vmin;
> +	if (i == dfs->dfs_table_size)
> +		new_freq = dfs->max_freq_at_vmin;
>  	else
> -		new_freq = isp->dfs->dfs_table[i].isp_freq;
> +		new_freq = dfs->dfs_table[i].isp_freq;
>  

you can eliminate the last block by setting

 new_freq = dfs->max_freq_at_vmin;

  for(i=0;....) {
        ....
	new_freq = dfs->dfs_table[i].isp_freq;
	break;
}

unfortunately i have no good idea how to make the loop more readable.


re,
 wh


>  done:
>  	dev_dbg(isp->dev, "DFS target frequency=%d.\n", new_freq);