linux-kernel - Re: [PATCH 1/9] memory: atmel-ebi: use scoped device node handling to simplify error paths

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Message-ID: <0ad7c0a5-67d5-4a28-ba0c-76e7b96d1a81@linaro.org>
Date: Wed, 14 Aug 2024 19:56:39 +0200
From: Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>
To: Jonathan Cameron <Jonathan.Cameron@...wei.com>
Cc: Krzysztof Kozlowski <krzk@...nel.org>,
 Nicolas Ferre <nicolas.ferre@...rochip.com>,
 Alexandre Belloni <alexandre.belloni@...tlin.com>,
 Claudiu Beznea <claudiu.beznea@...on.dev>, Lukasz Luba
 <lukasz.luba@....com>, Alim Akhtar <alim.akhtar@...sung.com>,
 Maxime Coquelin <mcoquelin.stm32@...il.com>,
 Alexandre Torgue <alexandre.torgue@...s.st.com>,
 Thierry Reding <thierry.reding@...il.com>,
 Jonathan Hunter <jonathanh@...dia.com>,
 Santosh Shilimkar <ssantosh@...nel.org>, linux-kernel@...r.kernel.org,
 linux-arm-kernel@...ts.infradead.org, linux-pm@...r.kernel.org,
 linux-samsung-soc@...r.kernel.org, linux-stm32@...md-mailman.stormreply.com,
 linux-tegra@...r.kernel.org
Subject: Re: [PATCH 1/9] memory: atmel-ebi: use scoped device node handling to
 simplify error paths

On 14/08/2024 18:38, Jonathan Cameron wrote:
> On Mon, 12 Aug 2024 15:33:55 +0200
> Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org> wrote:
> 
>> Obtain the device node reference with scoped/cleanup.h to reduce error
>> handling and make the code a bit simpler.
>>
>> Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>
> 
> Hi,
> 
> Comments inline.
>> ---
>>  drivers/memory/atmel-ebi.c | 29 ++++++++++-------------------
>>  1 file changed, 10 insertions(+), 19 deletions(-)
>>
>> diff --git a/drivers/memory/atmel-ebi.c b/drivers/memory/atmel-ebi.c
>> index e8bb5f37f5cb..fcbfc2655d8d 100644
>> --- a/drivers/memory/atmel-ebi.c
>> +++ b/drivers/memory/atmel-ebi.c
>> @@ -6,6 +6,7 @@
>>   * Copyright (C) 2013 Jean-Jacques Hiblot <jjhiblot@...phandler.com>
>>   */
>>  
>> +#include <linux/cleanup.h>
>>  #include <linux/clk.h>
>>  #include <linux/io.h>
>>  #include <linux/mfd/syscon.h>
>> @@ -517,7 +518,7 @@ static int atmel_ebi_dev_disable(struct atmel_ebi *ebi, struct device_node *np)
>>  static int atmel_ebi_probe(struct platform_device *pdev)
>>  {
>>  	struct device *dev = &pdev->dev;
>> -	struct device_node *child, *np = dev->of_node, *smc_np;
>> +	struct device_node *child, *np = dev->of_node;
>>  	struct atmel_ebi *ebi;
>>  	int ret, reg_cells;
>>  	struct clk *clk;
>> @@ -541,30 +542,24 @@ static int atmel_ebi_probe(struct platform_device *pdev)
>>  
>>  	ebi->clk = clk;
>>  
>> -	smc_np = of_parse_phandle(dev->of_node, "atmel,smc", 0);
>> +	struct device_node *smc_np __free(device_node) = of_parse_phandle(dev->of_node,
>> +									  "atmel,smc", 0);
> Trivial:
> I'd line break this as
>> +	struct device_node *smc_np __free(device_node) =
> 		of_parse_phandle(dev->of_node, "atmel,smc", 0);

Yeah, I have troubles with this constructor+destructor syntaxes. They
are way past 80 and 100 column, so maybe indeed should be wrapped at '='.

> 
>>  
>>  	ebi->smc.regmap = syscon_node_to_regmap(smc_np);
>> -	if (IS_ERR(ebi->smc.regmap)) {
>> -		ret = PTR_ERR(ebi->smc.regmap);
>> -		goto put_node;
>> -	}
>> +	if (IS_ERR(ebi->smc.regmap))
>> +		return PTR_ERR(ebi->smc.regmap);
>>  
>>  	ebi->smc.layout = atmel_hsmc_get_reg_layout(smc_np);
>> -	if (IS_ERR(ebi->smc.layout)) {
>> -		ret = PTR_ERR(ebi->smc.layout);
>> -		goto put_node;
>> -	}
>> +	if (IS_ERR(ebi->smc.layout))
>> +		return PTR_ERR(ebi->smc.layout);
>>  
>>  	ebi->smc.clk = of_clk_get(smc_np, 0);
>>  	if (IS_ERR(ebi->smc.clk)) {
>> -		if (PTR_ERR(ebi->smc.clk) != -ENOENT) {
>> -			ret = PTR_ERR(ebi->smc.clk);
>> -			goto put_node;
>> -		}
>> +		if (PTR_ERR(ebi->smc.clk) != -ENOENT)
>> +			return PTR_ERR(ebi->smc.clk);
>>  
>>  		ebi->smc.clk = NULL;
>>  	}
>> -	of_node_put(smc_np);
> 
> The large change in scope is a bit inelegant as it now hangs on to
> the smc_np much longer than before.
> 
> Maybe it's worth pulling out the modified code as a 
> atem_eb_probe_smc(struct device_node *smc_np, struct atmel_ebi_smc *smc )
> 
> or something like with a struct_group to define the atmel_ebi_smc
> 
> That would keep the tight scope for the data and generally simplify it
> a bit.


Are you speaking about any particular code optimization/performance
concerns or readability? Because scope in the latter, I believe, is not
the problem here. The entire point of __free() is that you do not care
about scope of variable or destructor. You know it will be freed, sooner
or later. If it happens later - no problem, anyway we don't have to
"think" about this variable or cleaning up because of __free().

Best regards,
Krzysztof