linux-kernel - Re: [PATCH 2/2] Bluetooth: btbcm: automate node cleanup in btbcm_get_board

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Message-ID: <d9fcd228-8198-4e4c-8752-e950ab598013@kernel.org>
Date: Thu, 31 Oct 2024 12:30:42 +0100
From: Krzysztof Kozlowski <krzk@...nel.org>
To: Javier Carrasco <javier.carrasco.cruz@...il.com>,
 Marcel Holtmann <marcel@...tmann.org>,
 Luiz Augusto von Dentz <luiz.dentz@...il.com>,
 Linus Walleij <linus.walleij@...aro.org>
Cc: linux-bluetooth@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/2] Bluetooth: btbcm: automate node cleanup in
 btbcm_get_board_name()

On 31/10/2024 12:14, Krzysztof Kozlowski wrote:
> On 31/10/2024 12:10, Javier Carrasco wrote:
>> On 31/10/2024 12:08, Krzysztof Kozlowski wrote:
>>> On 30/10/2024 16:46, Javier Carrasco wrote:
>>>> Switch to a more robust approach by automating the node release when it
>>>> goes out of scope, removing the need for explicit calls to
>>>> of_node_put().
>>>>
>>>> Signed-off-by: Javier Carrasco <javier.carrasco.cruz@...il.com>
>>>> ---
>>>>  drivers/bluetooth/btbcm.c | 8 ++------
>>>>  1 file changed, 2 insertions(+), 6 deletions(-)
>>>>
>>>> diff --git a/drivers/bluetooth/btbcm.c b/drivers/bluetooth/btbcm.c
>>>> index 400c2663d6b0..a1153ada74d2 100644
>>>> --- a/drivers/bluetooth/btbcm.c
>>>> +++ b/drivers/bluetooth/btbcm.c
>>>> @@ -541,23 +541,19 @@ static const struct bcm_subver_table bcm_usb_subver_table[] = {
>>>>  static const char *btbcm_get_board_name(struct device *dev)
>>>>  {
>>>>  #ifdef CONFIG_OF
>>>> -	struct device_node *root;
>>>> +	struct device_node *root __free(device_node) = of_find_node_by_path("/");
>>>>  	char *board_type;
>>>>  	const char *tmp;
>>>>  
>>>> -	root = of_find_node_by_path("/");
>>>>  	if (!root)
>>>>  		return NULL;
>>>>  
>>>> -	if (of_property_read_string_index(root, "compatible", 0, &tmp)) {
>>>> -		of_node_put(root);
>>>
>>> You just added this. Don't add code which is immediately removed. It's a
>>> noop or wrong code.
>>>
>>>
>>>
>>> Best regards,
>>> Krzysztof
>>>
>>
>> Exactly, I added that code to fix the issue in stable kernels that don't
> 
> Then send backport for stable.
> 
>> support the __free() macro, and then I removed it to use a safer
>> approach from now on.
> 
> This is not correct approach. We work here on mainline and in mainline
> this is one logical change: fixing issue. Whether you fix issue with
> of_node_put or cleanup or by removing of_find_node_by_path() call, it
> does not matter. All of these are fixing the same, one issue.
> 
> If you think about stable kernels, then work on backports, not inflate
> mainline kernel with multiple commits doing the same, creating
> artificial history.
> 

And to clarify even more: these stable backports are close to useless,
because it does not matter for them. No impact, not much benefits,
nothing improved for users/developers. There is no need to backport
them, although of course there is no loss by doing so. Therefore entire
dance affects mainline kernel without any real benefits for stable.

Your split suggests you don't really know what this dropping reference
is for.

Best regards,
Krzysztof