diff mbox

[v2] i2c-core: One function call less in acpi_i2c_space_handler() after error detection

Message ID 567E3CF3.10606@users.sourceforge.net
State Rejected
Headers show

Commit Message

SF Markus Elfring Dec. 26, 2015, 7:08 a.m. UTC 
From: Markus Elfring <elfring@users.sourceforge.net>
Date: Sat, 26 Dec 2015 08:00:52 +0100

The kfree() function was called in one case by the
acpi_i2c_space_handler() function during error handling
even if the passed variable "client" contained a null pointer.

Implementation details could be improved by the adjustment of jump targets
according to the Linux coding style convention.

This issue was detected by using the Coccinelle software.

Signed-off-by: Markus Elfring <elfring@users.sourceforge.net>
---
 drivers/i2c/i2c-core.c | 12 ++++++------
 1 file changed, 6 insertions(+), 6 deletions(-)

Comments

Wolfram Sang Dec. 26, 2015, 7:48 a.m. UTC | #1 
> The kfree() function was called in one case by the
> acpi_i2c_space_handler() function during error handling
> even if the passed variable "client" contained a null pointer.

This is OK. kfree() is known to be NULL-tolerant and we rely on it in
various places to keep the code simpler.
SF Markus Elfring Dec. 26, 2015, 8:52 a.m. UTC | #2 
>> The kfree() function was called in one case by the
>> acpi_i2c_space_handler() function during error handling
>> even if the passed variable "client" contained a null pointer.
> 
> This is OK. kfree() is known to be NULL-tolerant and we rely on it in
> various places to keep the code simpler.

I would appreciate if an unnecessary function call can be avoided here
so that the affected exception handling can become also a bit more efficient.

Regards,
Markus
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Wolfram Sang Dec. 26, 2015, 6:41 p.m. UTC | #3 
On Sat, Dec 26, 2015 at 09:52:11AM +0100, SF Markus Elfring wrote:
> >> The kfree() function was called in one case by the
> >> acpi_i2c_space_handler() function during error handling
> >> even if the passed variable "client" contained a null pointer.
> > 
> > This is OK. kfree() is known to be NULL-tolerant and we rely on it in
> > various places to keep the code simpler.
> 
> I would appreciate if an unnecessary function call can be avoided here
> so that the affected exception handling can become also a bit more efficient.

Simpler code is easier to maintain. See your patch, you didn't get it
correctly at your first try. Also, this is not a hot path, so I see
it as a micro-optimization also adding complexity. I don't favor that.
SF Markus Elfring Dec. 26, 2015, 7:30 p.m. UTC | #4 
>> I would appreciate if an unnecessary function call can be avoided here
>> so that the affected exception handling can become also a bit more efficient.
> 
> Simpler code is easier to maintain.

There are different opinions available around the desired simplicity.


> See your patch, you didn't get it correctly at your first try.

I wonder myself about the circumstances on how my incomplete update suggestion
did happen.


> Also, this is not a hot path,

I'm curious if approaches around better exception handling can eventually become
a "hot topic".


> so I see it as a micro-optimization

I can agree to this view for this function implementation.

 
> also adding complexity.

There are the usual software development trade-offs.


> I don't favor that.

Thanks for your constructive feedback.

Is an identifier like "free_client" a bit nicer (according to the Linux coding
style recommendations) than the short jump label "err" in the discussed use case?

Regards,
Markus
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diff mbox

Patch

diff --git a/drivers/i2c/i2c-core.c b/drivers/i2c/i2c-core.c
index 7349b00..9996531 100644
--- a/drivers/i2c/i2c-core.c
+++ b/drivers/i2c/i2c-core.c
@@ -313,18 +313,18 @@  acpi_i2c_space_handler(u32 function, acpi_physical_address command,
 	client = kzalloc(sizeof(*client), GFP_KERNEL);
 	if (!client) {
 		ret = AE_NO_MEMORY;
-		goto err;
+		goto free_ares;
 	}
 
 	if (!value64 || ares->type != ACPI_RESOURCE_TYPE_SERIAL_BUS) {
 		ret = AE_BAD_PARAMETER;
-		goto err;
+		goto free_client;
 	}
 
 	sb = &ares->data.i2c_serial_bus;
 	if (sb->type != ACPI_RESOURCE_SERIAL_TYPE_I2C) {
 		ret = AE_BAD_PARAMETER;
-		goto err;
+		goto free_client;
 	}
 
 	client->adapter = adapter;
@@ -401,13 +401,13 @@  acpi_i2c_space_handler(u32 function, acpi_physical_address command,
 	default:
 		pr_info("protocol(0x%02x) is not supported.\n", accessor_type);
 		ret = AE_BAD_PARAMETER;
-		goto err;
+		goto free_client;
 	}
 
 	gsb->status = status;
-
- err:
+free_client:
 	kfree(client);
+free_ares:
 	ACPI_FREE(ares);
 	return ret;
 }