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Message-ID: <2166fc66-9340-4e8c-8662-17a19a7d8ce6@linaro.org>
Date: Sat, 20 Apr 2024 13:13:57 +0200
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Subject: Re: [PATCH v1 1/2] Revert "Bluetooth: hci_qca: don't use
 IS_ERR_OR_NULL() with gpiod_get_optional()"
To: quic_zijuhu <quic_zijuhu@quicinc.com>, luiz.dentz@gmail.com,
 luiz.von.dentz@intel.com, marcel@holtmann.org
Cc: linux-bluetooth@vger.kernel.org, wt@penguintechs.org,
 bartosz.golaszewski@linaro.org
References: <1713449192-25926-1-git-send-email-quic_zijuhu@quicinc.com>
 <1713449192-25926-2-git-send-email-quic_zijuhu@quicinc.com>
 <83a1c837-e403-4da2-83c6-ee3dedbc1fe0@linaro.org>
 <7c5b85ca-e897-4798-97e7-955478c57d12@quicinc.com>
 <52394d97-04c3-4f77-aaae-f1e152cd5632@linaro.org>
 <0dca7c9b-6a97-4171-9b0c-5b806a4e8a60@quicinc.com>
 <4e4d8ee0-fbbe-4dc7-b40b-b983f9f39539@linaro.org>
 <01677a26-ea91-47cc-bdc4-283cf313d8e4@quicinc.com>
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From: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
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In-Reply-To: <01677a26-ea91-47cc-bdc4-283cf313d8e4@quicinc.com>
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On 20/04/2024 07:25, quic_zijuhu wrote:
> On 4/19/2024 9:49 PM, Krzysztof Kozlowski wrote:
> 
> Hi Krzysztof,bartosz,
> 
> let me summarize our discussion here in order to reduce unneccessary
> disagreements here.
> 
> 1) i only revert your change IS_ERR() to my change IS_ERR_OR_NULL.
> 
> 2) your change will cause serious regression issues for many lunched
> products

Instead of repeating every time "serious regression" can you actually
explain the problem?
None of commit messages from v3 help there.

> 
> 3) we only need to discuss how to handle devm_gpiod_get_optional(...,
> "enable", ...) returning NULL since this is only difference between your
> change and mine.
> 
> 4) your change doesn't solve any actual issue and the reason you
> submitted is that "The optional variants for the gpiod_get() family of
> functions return NULL if the GPIO in question is not associated with
> this device, and should not treat it as error".
> 
> code applet of your merged change is shown by below link
> https://patchwork.kernel.org/project/bluetooth/patch/20240208164017.26699-1-brgl@bgdev.pl/#25705104
> 
> qcadev->bt_en = devm_gpiod_get_optional(&serdev->dev, "enable",
>  					       GPIOD_OUT_LOW);
> -		if (IS_ERR_OR_NULL(qcadev->bt_en)) {
> +		if (IS_ERR(qcadev->bt_en)) {
>  			dev_warn(&serdev->dev, "failed to acquire enable gpio\n");
>  			power_ctrl_enabled = false;
>  		}
> 
> 5) Original BT driver design agree with your point mentioned at 4), so
> for case "qcadev->bt_en == nullptr", qca_serdev_probe() don't do error
> return for this scenario and use dev_warn() instead of dev_err() to give
> user prompt.
> 
> 6) your wrong fix changes flag power_ctrl_enabled set logic and will
> cause serious BT regression issue, hope you will realize this point.

Sorry, not realized and you did not explain it. Neither above nor in
commit msg.

> 
> 
> i would like to give below extra comments even if these comments are
> irrelevant to the critical point of this issue mentioned at above 3)
> 
> A) you need to investigate it is a) the prompting approach or message
>  error or b) the if condition error even if if dev_err() is used to give
> prompt instead of dev_warn() in above 4).

What?

> 
> B) don't talk about how about devm_gpiod_get_optional() returning error
> case since it is meaningless as explained by above 3). also don't
> require a fix to fix another unreported issue. a fix is a good fix
> if it fix the issue in question and don't introduce new issue.

What?

> 
> C) per DTS property enable-gpios of BT, different soc types have
> different requirements, many are required and another many are NOT
> mandatory as shown be below link.
> https://git.kernel.org/pub/scm/linux/kernel/git/bluetooth/bluetooth-next.git/tree/Documentation/devicetree/bindings/net/bluetooth/qualcomm-bluetooth.yaml.
> 
> for a soc type which are attached to 3rd platform, customer doesn't
> would like to or are not able to congfig BT reset pin within DTS for QCA
> driver even if QC strongly suggest customer config it and also be marked
> as required within above DTS bindings spec link. i often meet this
> scenario. there are many of such lunched products.

So where is it documented? Where is it explained? Which binding or which
commit msg?

> 
> i will try to fix this issue due your change product by product in new
> patch thread based on this DTS comment.
> 
> D) you maybe ping me offline about this issue if you are a member of QC
> since you known "go/upstream"

Please keep all discussions public, unless your customer requires some
sort of confidentiality. Although even then I would argue that you can
hide company secrets and discuss about hardware.

Best regards,
Krzysztof