2016-12-07 14:59:52

by Arvind Yadav

Subject: [PATCH V1] hid: hid-multitouch:- No need of devm functions

In function mt_probe, the memory allocated for td->fields
is live within the function only. After the allocation
it is immediately freed with devm_kfree. There is no need
to allocate memory for td->fields with devm function so
replace devm_kzalloc with kzalloc and devm_kfree with kfree.

Signed-off-by: Arvind Yadav <[email protected]>
---
drivers/hid/hid-multitouch.c | 17 +++++++++++------
1 file changed, 11 insertions(+), 6 deletions(-)

diff --git a/drivers/hid/hid-multitouch.c b/drivers/hid/hid-multitouch.c
index fb6f1f4..13ea309 100644
--- a/drivers/hid/hid-multitouch.c
+++ b/drivers/hid/hid-multitouch.c
@@ -1126,11 +1126,11 @@ static int mt_probe(struct hid_device *hdev, const struct hid_device_id *id)
td->mt_report_id = -1;
hid_set_drvdata(hdev, td);

- td->fields = devm_kzalloc(&hdev->dev, sizeof(struct mt_fields),
- GFP_KERNEL);
+ td->fields = kzalloc(sizeof(struct mt_fields), GFP_KERNEL);
if (!td->fields) {
dev_err(&hdev->dev, "cannot allocate multitouch fields data\n");
- return -ENOMEM;
+ ret = -ENOMEM;
+ goto error_nomem;
}

if (id->vendor == HID_ANY_ID && id->product == HID_ANY_ID)
@@ -1138,11 +1138,11 @@ static int mt_probe(struct hid_device *hdev, const struct hid_device_id *id)

ret = hid_parse(hdev);
if (ret != 0)
- return ret;
+ goto error_free;

ret = hid_hw_start(hdev, HID_CONNECT_DEFAULT);
if (ret)
- return ret;
+ goto error_free;

ret = sysfs_create_group(&hdev->dev.kobj, &mt_attribute_group);
if (ret)
@@ -1153,10 +1153,15 @@ static int mt_probe(struct hid_device *hdev, const struct hid_device_id *id)
mt_set_input_mode(hdev);

/* release .fields memory as it is not used anymore */
- devm_kfree(&hdev->dev, td->fields);
+ kfree(td->fields);
td->fields = NULL;

return 0;
+
+error_free:
+ kfree(td->fields);
+error_nomem:
+ return ret;
}

#ifdef CONFIG_PM
--
2.7.4

2016-12-13 08:25:02

by Benjamin Tissoires

Subject: Re: [PATCH V1] hid: hid-multitouch:- No need of devm functions

On Dec 07 2016 or thereabouts, Arvind Yadav wrote:
> In function mt_probe, the memory allocated for td->fields
> is live within the function only. After the allocation
> it is immediately freed with devm_kfree. There is no need
> to allocate memory for td->fields with devm function so
> replace devm_kzalloc with kzalloc and devm_kfree with kfree.
>
> Signed-off-by: Arvind Yadav <[email protected]>
> ---

Please don't.

It's true that the buffer is only used temporary, but there are 2
reasons for that:
- the driver uses devm everywhere
- the return path is simplified by using devm

And here, the error code path will be more complex for no gain.

Cheers,
Benjamin

> drivers/hid/hid-multitouch.c | 17 +++++++++++------
> 1 file changed, 11 insertions(+), 6 deletions(-)
>
> diff --git a/drivers/hid/hid-multitouch.c b/drivers/hid/hid-multitouch.c
> index fb6f1f4..13ea309 100644
> --- a/drivers/hid/hid-multitouch.c
> +++ b/drivers/hid/hid-multitouch.c
> @@ -1126,11 +1126,11 @@ static int mt_probe(struct hid_device *hdev, const struct hid_device_id *id)
> td->mt_report_id = -1;
> hid_set_drvdata(hdev, td);
>
> - td->fields = devm_kzalloc(&hdev->dev, sizeof(struct mt_fields),
> - GFP_KERNEL);
> + td->fields = kzalloc(sizeof(struct mt_fields), GFP_KERNEL);
> if (!td->fields) {
> dev_err(&hdev->dev, "cannot allocate multitouch fields data\n");
> - return -ENOMEM;
> + ret = -ENOMEM;
> + goto error_nomem;
> }
>
> if (id->vendor == HID_ANY_ID && id->product == HID_ANY_ID)
> @@ -1138,11 +1138,11 @@ static int mt_probe(struct hid_device *hdev, const struct hid_device_id *id)
>
> ret = hid_parse(hdev);
> if (ret != 0)
> - return ret;
> + goto error_free;
>
> ret = hid_hw_start(hdev, HID_CONNECT_DEFAULT);
> if (ret)
> - return ret;
> + goto error_free;
>
> ret = sysfs_create_group(&hdev->dev.kobj, &mt_attribute_group);
> if (ret)
> @@ -1153,10 +1153,15 @@ static int mt_probe(struct hid_device *hdev, const struct hid_device_id *id)
> mt_set_input_mode(hdev);
>
> /* release .fields memory as it is not used anymore */
> - devm_kfree(&hdev->dev, td->fields);
> + kfree(td->fields);
> td->fields = NULL;
>
> return 0;
> +
> +error_free:
> + kfree(td->fields);
> +error_nomem:
> + return ret;
> }
>
> #ifdef CONFIG_PM
> --
> 2.7.4
>