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

From: "Russell King (Oracle)" <linux@armlinux.org.uk>
To: Ilkka Koskinen <ilkka@os.amperecomputing.com>
Cc: lorenzo.pieralisi@arm.com, guohanjun@huawei.com,
	sudeep.holla@arm.com, rafael@kernel.org, lenb@kernel.org,
	robert.moore@intel.com, linux-acpi@vger.kernel.org,
	linux-arm-kernel@lists.infradead.org,
	linux-kernel@vger.kernel.org, devel@acpica.org,
	patches@amperecomputing.com, scott@os.amperecomputing.com,
	darren@os.amperecomputing.com
Subject: Re: [PATCH 2/2] ACPI: AGDI: Add driver for Arm Generic Diagnostic Dump and Reset device
Date: Thu, 9 Dec 2021 16:36:15 +0000	[thread overview]
Message-ID: <YbIwfzND2R4WyQO7@shell.armlinux.org.uk> (raw)
In-Reply-To: <20211203024311.49865-3-ilkka@os.amperecomputing.com>

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.

-- 
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