linux-kernel - Re: [PATCH V2 1/2] soc: qcom: aoss: Expose send for generic usecase

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Message-ID: <YHYJVjvjUyXtrNmC@builder.lan>
Date:   Tue, 13 Apr 2021 16:12:54 -0500
From:   Bjorn Andersson <bjorn.andersson@...aro.org>
To:     Deepak Kumar Singh <deesin@....qualcomm.com>
Cc:     clew@...eaurora.org, sibis@...eaurora.org,
        linux-kernel@...r.kernel.org, linux-arm-msm@...r.kernel.org,
        linux-remoteproc@...r.kernel.org,
        Deepak Kumar Singh <deesin@...eaurora.org>,
        Andy Gross <agross@...nel.org>
Subject: Re: [PATCH V2 1/2] soc: qcom: aoss: Expose send for generic usecase

On Thu 08 Apr 23:39 CDT 2021, Deepak Kumar Singh wrote:
[..]
> +/**
> + * qmp_get() - get a qmp handle from a device
> + * @dev: client device pointer
> + *
> + * Return: handle to qmp device on success, ERR_PTR() on failure
> + */
> +struct qmp *qmp_get(struct device *dev)
> +{
> +	struct platform_device *pdev;
> +	struct device_node *np;
> +	struct qmp *qmp;
> +
> +	if (!dev || !dev->of_node)
> +		return ERR_PTR(-EINVAL);
> +
> +	np = of_parse_phandle(dev->of_node, "qcom,qmp", 0);
> +	if (!np)
> +		return ERR_PTR(-ENODEV);
> +
> +	pdev = of_find_device_by_node(np);
> +	if (!pdev)
> +		return ERR_PTR(-EINVAL);
> +
> +	qmp = platform_get_drvdata(pdev);
> +	return qmp ? qmp : ERR_PTR(-EPROBE_DEFER);
> +}
> +EXPORT_SYMBOL(qmp_get);
> +
> +void qmp_put(struct platform_device *pdev)
> +{
> +	platform_device_put(pdev);

I was expecting that the devres allocated struct qmp would stick around
until the struct device's release callback came. As described in my
answer to Mani yesterday I was wrong.

As such you need to make sure that struct qmp stays around until
qmp_remove() and all qmp_put() calls has been made.

I presume a reasonable way to achieve this is to not use devm to
allocate our struct qmp, add a kref to the object. So this would have to
be a kref_put() on that instead of the platform_device_put() I asked you
to implement here.

Sorry about that.


The rest of the patch looks good.

Regards,
Bjorn