[PATCH] regulator: aat2870-regulator: replace division condition with direct comparison

[PATCH] regulator: aat2870-regulator: replace division condition with direct comparison

[Suraj Sonawane]

Fix an issue detected by the Smatch tool:

drivers/regulator/aat2870-regulator.c:142 aat2870_get_regulator() warn:
replace divide condition '(id - 1) / 2' with '(id - 1) >= 2'

The division '(id - 1) / 2' was used to check if the regulator ID
is greater than or equal to 2, which can be confusing and less
readable. Replacing it with '(id - 1) >= 2' makes the code clearer
by directly comparing the regulator ID. This change also removes
reliance on integer division, which could be harder to understand
and may introduce subtle bugs.

Signed-off-by: Suraj Sonawane <surajsonawane0215@gmail.com>
---
 drivers/regulator/aat2870-regulator.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/regulator/aat2870-regulator.c b/drivers/regulator/aat2870-regulator.c
index 970d86f2b..b48d2987a 100644
--- a/drivers/regulator/aat2870-regulator.c
+++ b/drivers/regulator/aat2870-regulator.c
@@ -139,7 +139,7 @@ static struct aat2870_regulator *aat2870_get_regulator(int id)
 	ri->enable_shift = id - AAT2870_ID_LDOA;
 	ri->enable_mask = 0x1 << ri->enable_shift;
 
-	ri->voltage_addr = (id - AAT2870_ID_LDOA) / 2 ?
+	ri->voltage_addr = (id - AAT2870_ID_LDOA) >= 2 ?
 			   AAT2870_LDO_CD : AAT2870_LDO_AB;
 	ri->voltage_shift = (id - AAT2870_ID_LDOA) % 2 ? 0 : 4;
 	ri->voltage_mask = 0xF << ri->voltage_shift;
-- 
2.34.1

Re: [PATCH] regulator: aat2870-regulator: replace division condition with direct comparison

[Mark Brown]

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On Wed, Nov 13, 2024 at 01:50:41AM +0530, Suraj Sonawane wrote:
> Fix an issue detected by the Smatch tool:
> 
> drivers/regulator/aat2870-regulator.c:142 aat2870_get_regulator() warn:
> replace divide condition '(id - 1) / 2' with '(id - 1) >= 2'
> 
> The division '(id - 1) / 2' was used to check if the regulator ID
> is greater than or equal to 2, which can be confusing and less
> readable. Replacing it with '(id - 1) >= 2' makes the code clearer

This is absolute nonsense, the tool should be fixed instead.  Writing a 
division as a shift when the intent is a division is a microoptimisation
which modern compilers really should figure out where it's relevant.

> -	ri->voltage_addr = (id - AAT2870_ID_LDOA) / 2 ?
> +	ri->voltage_addr = (id - AAT2870_ID_LDOA) >= 2 ?
>  			   AAT2870_LDO_CD : AAT2870_LDO_AB;

Neither version of this is particularly readable, but the new form here
seems fairly clearly worse rather than better.

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Re: [PATCH] regulator: aat2870-regulator: replace division condition with direct comparison

[Suraj Sonawane]

On 13/11/24 19:09, Mark Brown wrote:
> On Wed, Nov 13, 2024 at 01:50:41AM +0530, Suraj Sonawane wrote:
>> Fix an issue detected by the Smatch tool:
>>
>> drivers/regulator/aat2870-regulator.c:142 aat2870_get_regulator() warn:
>> replace divide condition '(id - 1) / 2' with '(id - 1) >= 2'
>>
>> The division '(id - 1) / 2' was used to check if the regulator ID
>> is greater than or equal to 2, which can be confusing and less
>> readable. Replacing it with '(id - 1) >= 2' makes the code clearer
> 
> This is absolute nonsense, the tool should be fixed instead.  Writing a
> division as a shift when the intent is a division is a microoptimisation
> which modern compilers really should figure out where it's relevant.
> 
>> -	ri->voltage_addr = (id - AAT2870_ID_LDOA) / 2 ?
>> +	ri->voltage_addr = (id - AAT2870_ID_LDOA) >= 2 ?
>>   			   AAT2870_LDO_CD : AAT2870_LDO_AB;
> 
> Neither version of this is particularly readable, but the new form here
> seems fairly clearly worse rather than better.
Hi Mark,

Thank you for your feedback. I see your point about the original code 
being clear enough and changing it as suggested making it worse.

Best,
Suraj