linux-kernel - Re: [PATCH 2/2] ACPI: AGDI: Add driver for Arm Generic Diagnostic Dump and Reset device

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Message-ID: <YbIwfzND2R4WyQO7@shell.armlinux.org.uk>
Date:   Thu, 9 Dec 2021 16:36:15 +0000
From:   "Russell King (Oracle)" <linux@...linux.org.uk>
To:     Ilkka Koskinen <ilkka@...amperecomputing.com>
Cc:     lorenzo.pieralisi@....com, guohanjun@...wei.com,
        sudeep.holla@....com, rafael@...nel.org, lenb@...nel.org,
        robert.moore@...el.com, linux-acpi@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        devel@...ica.org, patches@...erecomputing.com,
        scott@...amperecomputing.com, darren@...amperecomputing.com
Subject: Re: [PATCH 2/2] ACPI: AGDI: Add driver for Arm Generic Diagnostic
 Dump and Reset device

Hi,

On Thu, Dec 02, 2021 at 06:43:11PM -0800, Ilkka Koskinen wrote:
> +static int __init agdi_init(void)
> +{
> +	int ret;
> +	acpi_status status;
> +	struct acpi_table_agdi *agdi_table;
> +	struct agdi_data *pdata;
> +	struct platform_device *pdev;
> +
> +	if (acpi_disabled)
> +		return 0;
> +
> +	status = acpi_get_table(ACPI_SIG_AGDI, 0,
> +				(struct acpi_table_header **) &agdi_table);
> +	if (ACPI_FAILURE(status))
> +		return -ENODEV;
> +
> +	pdata = kzalloc(sizeof(*pdata), GFP_ATOMIC);

Why does this need to be GFP_ATOMIC? Also, struct agdi_data is a single
int in size, why do you need to kzalloc() it?

> +	if (!pdata) {
> +		ret = -ENOMEM;
> +		goto err_put_table;
> +	}
> +
> +	if (agdi_table->flags & ACPI_AGDI_SIGNALING_MODE) {
> +		pr_warn("Interrupt signaling is not supported");
> +		ret = -ENODEV;
> +		goto err_free_pdata;
> +	}
> +
> +	pdata->sdei_event = agdi_table->sdei_event;
> +
> +	pdev = platform_device_register_data(NULL, "agdi", 0, pdata, sizeof(*pdata));

platform_device_register_data() uses kmemdup() internally with the
platform data, meaning it takes a copy of the platform data. There is
no need for the pdata allocation to persist past this point. Hence,
given that it is a single int in size, you may as well put
"struct agdi_data" on the stack.

Thanks.

-- 
RMK's Patch system: https://www.armlinux.org.uk/developer/patches/
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