linux-kernel - Re: [PATCH 2/3] soc: Add VIA/WonderMedia SoC identification driver

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Message-ID: <c38b3dde-f4ea-4812-a673-137d4727aefc@kernel.org>
Date: Fri, 25 Apr 2025 12:24:24 +0200
From: Krzysztof Kozlowski <krzk@...nel.org>
To: Alexey Charkov <alchark@...il.com>, Rob Herring <robh@...nel.org>,
 Krzysztof Kozlowski <krzk+dt@...nel.org>, Conor Dooley <conor+dt@...nel.org>
Cc: devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
 linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH 2/3] soc: Add VIA/WonderMedia SoC identification driver

On 23/04/2025 21:18, Alexey Charkov wrote:
> Add a small SOC bus driver to parse the chip ID and revision made
> available on VIA/WonderMedia SoCs via their system configuration
> controller's SCC_ID register.


...

> +#include <linux/io.h>
> +#include <linux/of.h>
> +#include <linux/of_address.h>
> +#include <linux/of_platform.h>
> +#include <linux/platform_device.h>
> +#include <linux/slab.h>
> +#include <linux/sys_soc.h>
> +
> +static struct {

I think const by convention is placed here - right after static. It
should be equivalent, just convention.

> +	const char *name;
> +	const unsigned long id;
> +} const chip_id_table[] = {
> +	/* VIA */
> +	{ "VT8420", 0x3300 },
> +	{ "VT8430", 0x3357 },
> +	{ "VT8500", 0x3400 },
> +
> +	/* WonderMedia */
> +	{ "WM8425", 0x3429 },
> +	{ "WM8435", 0x3437 },
> +	{ "WM8440", 0x3451 },
> +	{ "WM8505", 0x3426 },
> +	{ "WM8650", 0x3465 },
> +	{ "WM8750", 0x3445 },
> +	{ "WM8850", 0x3481 },
> +	{ "WM8880", 0x3498 },
> +};
> +
> +static const char *sccid_to_name(unsigned long sccid)
> +{
> +	unsigned long id = sccid >> 16;
> +	unsigned int i;
> +
> +	for (i = 0 ; i < ARRAY_SIZE(chip_id_table) ; ++i) {
> +		if (chip_id_table[i].id == id)
> +			return chip_id_table[i].name;
> +	}
> +
> +	return "Unknown";
> +}
> +
> +static const char *sccid_to_rev(unsigned long sccid)
> +{
> +	char letter, digit;
> +
> +	letter = (sccid >> 8) & 0xf;
> +	letter = (letter - 1) + 'A';
> +
> +	digit = sccid & 0xff;
> +	digit = (digit - 1) + '0';
> +
> +	return kasprintf(GFP_KERNEL, "%c%c", letter, digit);
> +}
> +
> +static int __init wmt_socinfo_init(void)
> +{
> +	struct soc_device_attribute *attrs;
> +	struct soc_device *soc_dev;
> +	struct device_node *np;
> +	void __iomem *reg;
> +	unsigned long sccid;
> +	const char *machine = NULL;
> +
> +	np = of_find_compatible_node(NULL, NULL, "via,scc-id");
> +	if (!of_device_is_available(np)) {
> +		of_node_put(np);
> +		return -ENODEV;
> +	}
> +
> +	reg = of_iomap(np, 0);

of_node_put(np) here... although this will be dropped (see below)


> +	if (!reg) {
> +		of_node_put(np);
> +		return -ENODEV;
> +	}
> +	sccid = readl(reg);
> +	iounmap(reg);
> +
> +	attrs = kzalloc(sizeof(*attrs), GFP_KERNEL);
> +	if (!attrs)
> +		return -ENODEV;
> +
> +	/*
> +	 * Machine: VIA APC Rock
> +	 * Family: WM8850
> +	 * Revision: A2
> +	 * SoC ID: raw silicon revision id (0x34810103)
> +	 */
> +
> +	np = of_find_node_by_path("/");
> +	of_property_read_string(np, "model", &machine);
> +	if (machine)
> +		attrs->machine = kstrdup(machine, GFP_KERNEL);
> +	of_node_put(np);
> +
> +	attrs->family = sccid_to_name(sccid);
> +	attrs->revision = sccid_to_rev(sccid);
> +	attrs->soc_id = kasprintf(GFP_KERNEL, "%08lx", sccid);
> +
> +	soc_dev = soc_device_register(attrs);
> +	if (IS_ERR(soc_dev)) {
> +		kfree(attrs->machine);
> +		kfree(attrs->soc_id);
> +		kfree(attrs->revision);
> +		kfree(attrs);
> +		return PTR_ERR(soc_dev);
> +	}
> +
> +	pr_info("VIA/WonderMedia %s rev %s (%s)\n",
> +			attrs->family,
> +			attrs->revision,
> +			attrs->soc_id);
> +
> +	return 0;
> +}
> +early_initcall(wmt_socinfo_init);

No, this does not scale. This is supposed to be module_platform_driver
instead of manually re-ordering code. Then all your memory allocations
become devm, printks become dev_xxx and you can simplify it.


> 


Best regards,
Krzysztof