[PATCHv3 2/6] acpi/cppc: Ensure only supported CPPC sysfs entries are created

["Natarajan, Janakarajan" <Janakarajan.Natarajan@amd.com>]

Add attributes only for registers that are supported by the platform.
This prevents unsupported, optional registers from having sysfs entries
created.

Signed-off-by: Janakarajan Natarajan <Janakarajan.Natarajan@amd.com>
---
 drivers/acpi/cppc_acpi.c | 82 +++++++++++++++++++++++++++++++++-------
 1 file changed, 68 insertions(+), 14 deletions(-)

diff --git a/drivers/acpi/cppc_acpi.c b/drivers/acpi/cppc_acpi.c
index c43de65531ae..53a9dc9960b6 100644
--- a/drivers/acpi/cppc_acpi.c
+++ b/drivers/acpi/cppc_acpi.c
@@ -183,22 +183,8 @@ static ssize_t show_feedback_ctrs(struct kobject *kobj,
 }
 define_one_cppc_ro(feedback_ctrs);
 
-static struct attribute *cppc_attrs[] = {
-	&feedback_ctrs.attr,
-	&reference_perf.attr,
-	&wraparound_time.attr,
-	&highest_perf.attr,
-	&lowest_perf.attr,
-	&lowest_nonlinear_perf.attr,
-	&nominal_perf.attr,
-	&nominal_freq.attr,
-	&lowest_freq.attr,
-	NULL
-};
-
 static struct kobj_type cppc_ktype = {
 	.sysfs_ops = &kobj_sysfs_ops,
-	.default_attrs = cppc_attrs,
 };
 
 static int check_pcc_chan(int pcc_ss_id, bool chk_err_bit)
@@ -733,6 +719,69 @@ static bool is_buf_only(int reg_idx)
 				 CPC_SUP_BUFFER_ONLY(&cpc->cpc_regs[idx]) : \
 				 CPC_SUPPORTED(&cpc->cpc_regs[idx]))
 
+static int is_mandatory_reg(int reg_idx)
+{
+	switch (reg_idx) {
+	case HIGHEST_PERF:
+	case NOMINAL_PERF:
+	case LOW_NON_LINEAR_PERF:
+	case LOWEST_PERF:
+	case REFERENCE_CTR:
+	case DELIVERED_CTR:
+		return 1;
+	}
+
+	return 0;
+}
+
+#define MANDATORY_REG_CNT	6
+
+static int set_cppc_attrs(struct cpc_desc *cpc, int entries)
+{
+	int i, attr_i = 0, opt_reg_cnt;
+	static struct attribute **cppc_attrs;
+
+	cppc_attrs = kcalloc(entries, sizeof(*cppc_attrs), GFP_KERNEL);
+	if (!cppc_attrs)
+		return -ENOMEM;
+
+	/* Set optional regs */
+	opt_reg_cnt = entries - MANDATORY_REG_CNT;
+	for (i = 0; i < MAX_CPC_REG_ENT && attr_i < opt_reg_cnt; i++) {
+		if (is_mandatory_reg(i) || !REG_SUPPORTED(cpc, i))
+			continue;
+
+		switch (i) {
+		case NOMINAL_FREQ:
+			cppc_attrs[attr_i++] = &nominal_freq.attr;
+			break;
+		case LOWEST_FREQ:
+			cppc_attrs[attr_i++] = &lowest_freq.attr;
+			break;
+		case REFERENCE_PERF:
+			cppc_attrs[attr_i++] = &reference_perf.attr;
+			break;
+		case CTR_WRAP_TIME:
+			cppc_attrs[attr_i++] = &wraparound_time.attr;
+			break;
+		}
+	}
+
+	/* Set mandatory regs */
+	cppc_attrs[attr_i++] = &highest_perf.attr;
+	cppc_attrs[attr_i++] = &nominal_perf.attr;
+	cppc_attrs[attr_i++] = &lowest_nonlinear_perf.attr;
+	cppc_attrs[attr_i++] = &lowest_perf.attr;
+
+	/* Set feedback_ctr sysfs entry */
+	cppc_attrs[attr_i] = &feedback_ctrs.attr;
+
+	/* Set kobj_type member */
+	cppc_ktype.default_attrs = cppc_attrs;
+
+	return 0;
+}
+
 /**
  * acpi_cppc_processor_probe - Search for per CPU _CPC objects.
  * @pr: Ptr to acpi_processor containing this CPU's logical ID.
@@ -887,6 +936,10 @@ int acpi_cppc_processor_probe(struct acpi_processor *pr)
 	/* Plug PSD data into this CPU's CPC descriptor. */
 	per_cpu(cpc_desc_ptr, pr->id) = cpc_ptr;
 
+	ret = set_cppc_attrs(cpc_ptr, num_ent - 2);
+	if (ret)
+		goto out_free;
+
 	ret = kobject_init_and_add(&cpc_ptr->kobj, &cppc_ktype, &cpu_dev->kobj,
 			"acpi_cppc");
 	if (ret) {
@@ -948,6 +1001,7 @@ void acpi_cppc_processor_exit(struct acpi_processor *pr)
 			iounmap(addr);
 	}
 
+	kfree(cppc_ktype.default_attrs);
 	kobject_put(&cpc_ptr->kobj);
 	kfree(cpc_ptr);
 }
-- 
2.17.1