Re: [PATCH RFC 2/2] soc: Add a basic ACPI generic driver

[John Garry]

Hi Greg,

> > +
> > +#define pr_fmt(fmt) "SOC ACPI GENERIC: " fmt
>
> You have a device, why do you need pr_fmt()?

The only print in the code can be removed, below, so I need not worry 
about this, i.e. remove it.

> > +
> > +#include <linux/acpi.h>
> > +#include <linux/sys_soc.h>
> > +
> > +/*
> > + * Known platforms that fill in PPTT package ID structures according to
> > + * ACPI spec examples, that being:
> > + * - Custom driver attribute is in ID Type Structure VENDOR_ID member
> > + * - SoC id is in ID Type Structure LEVEL_2_ID member
> > + *    See ACPI SPEC 6.2 Table 5-154 for PPTT ID Type Structure
> > + */
> > +static struct acpi_platform_list plat_list[] = {
> > +	{"HISI  ", "HIP08   ", 0, ACPI_SIG_PPTT, all_versions},
> > +	{ } /* End */
> > +};
> > +
> > +struct acpi_generic_soc_struct {
> > +	struct soc_device_attribute dev_attr;
> > +	u32 vendor;
> > +};
> > +
> > +static ssize_t vendor_show(struct device *dev,
> > +			   struct device_attribute *attr,
> > +			   char *buf)
> > +{
> > +	struct acpi_generic_soc_struct *soc = dev_get_drvdata(dev);
> > +	u8 vendor_id[5] = {};
> > +
> > +	*(u32 *)vendor_id = soc->vendor;
> > +
> > +	return sprintf(buf, "%s\n", vendor_id);
> > +}
> > +
> > +static DEVICE_ATTR_RO(vendor);
> > +
> > +static __init int soc_acpi_generic_init(void)
> > +{
> > +	int index;
> > +
> > +	index = acpi_match_platform_list(plat_list);
> > +	if (index < 0)
> > +		return -ENOENT;
> > +
> > +	index = 0;
> > +	while (true) {
> > +		struct acpi_pptt_package_info info;
> > +
> > +		if (!acpi_pptt_get_package_info(index, &info)) {
> > +			struct soc_device_attribute *soc_dev_attr;
> > +			struct acpi_generic_soc_struct *soc;
> > +			struct soc_device *soc_dev;
> > +			u8 soc_id[9] = {};
> > +
> > +			*(u64 *)soc_id = info.LEVEL_2_ID;
> > +
> > +			soc = kzalloc(sizeof(*soc), GFP_KERNEL);
> > +			if (!soc)
> > +				return -ENOMEM;
> > +
> > +			soc_dev_attr = &soc->dev_attr;
> > +			soc_dev_attr->soc_id = kasprintf(GFP_KERNEL, "%s",
> > +							 soc_id);
> > +			if (!soc_dev_attr->soc_id) {
> > +				kfree(soc);
> > +				return -ENOMEM;
> > +			}
> > +			soc->vendor = info.vendor_id;
> > +
> > +			soc_dev = soc_device_register(soc_dev_attr);
> > +			if (IS_ERR(soc_dev)) {
> > +				int ret = PTR_ERR(soc_dev);
> > +
> > +				pr_info("could not register soc (%d) index=%d\n",
> > +					ret, index);
>
> pr_err()?

Yes, more appropriate.

> And shouldn't the core print out the error, not the person who calls it?

Sure, that would sounds reasonable, but I just wanted to get the index 
at which we fail. I could live without it.

> > +				kfree(soc_dev_attr->soc_id);
> > +				kfree(soc);
> > +				return ret;
> > +			}
> > +			dev_set_drvdata(soc_device_to_device(soc_dev), soc);
> > +			device_create_file(soc_device_to_device(soc_dev),
> > +					   &dev_attr_vendor);
>
> You just raced with userspace and lost.  Use the built-in api that I
> made _just_ because of SOC drivers to do this correctly.

Fine, there is the soc device custom attr group which I can use. But, as 
Arnd said, maybe we can drop this custom file.

Cheers,
John