[PATCH v2 3/3] Changing bios_args.data to be dynamically allocated

[Jorge Lopez <jorgealtxwork@gmail.com>]

The purpose of this patch is to remove 128 bytes buffer limitation
imposed in bios_args structure.

A limiting factor discovered during this investigation was the struct
bios_args.data size restriction.  The data member size limits all possible
WMI commands to those requiring buffer size of 128 bytes or less.
Several WMI commands and queries require a buffer size larger than 128
bytes hence limiting current and feature supported by the driver.
It is for this reason, struct bios_args.data changed and is dynamically
allocated.  hp_wmi_perform_query function changed to handle the memory
allocation and release of any required buffer size.

All changes were validated on a ZBook Workstation notebook. Additional
validation was included to ensure no other commands were failing or
incorrectly handled.

Signed-off-by: Jorge Lopez <jorge.lopez2@hp.com>

---
Based on the latest platform-drivers-x86.git/for-next
---
 drivers/platform/x86/hp-wmi.c | 67 +++++++++++++++++++++++------------
 1 file changed, 44 insertions(+), 23 deletions(-)

diff --git a/drivers/platform/x86/hp-wmi.c b/drivers/platform/x86/hp-wmi.c
index de715687021a..11c8e9b6e64a 100644
--- a/drivers/platform/x86/hp-wmi.c
+++ b/drivers/platform/x86/hp-wmi.c
@@ -83,12 +83,17 @@ enum hp_wmi_event_ids {
 	HPWMI_BATTERY_CHARGE_PERIOD	= 0x10,
 };
 
+/**
+ * struct bios_args buffer is dynamically allocated.  New WMI command types
+ * were introduced that exceeds 128-byte data size.  Changes to handle
+ * the data size allocation scheme were kept in hp_wmi_perform_qurey function.
+ */
 struct bios_args {
 	u32 signature;
 	u32 command;
 	u32 commandtype;
 	u32 datasize;
-	u8 data[128];
+	u8 data[0];
 };
 
 enum hp_wmi_commandtype {
@@ -258,39 +263,47 @@ static int hp_wmi_perform_query(int query, enum hp_wmi_command command,
 	struct bios_return *bios_return;
 	int actual_outsize;
 	union acpi_object *obj;
-	struct bios_args args = {
-		.signature = 0x55434553,
-		.command = command,
-		.commandtype = query,
-		.datasize = insize,
-		.data = { 0 },
-	};
-	struct acpi_buffer input = { sizeof(struct bios_args), &args };
+	size_t bios_args_size = sizeof(struct bios_args) + insize;
+	struct bios_args *args = NULL;
+	struct acpi_buffer input;
 	struct acpi_buffer output = { ACPI_ALLOCATE_BUFFER, NULL };
 	int ret = 0;
 
-	mid = encode_outsize_for_pvsz(outsize);
-	if (WARN_ON(mid < 0))
-		return mid;
+	args = kmalloc(bios_args_size, GFP_KERNEL);
+	if (!args)
+		return -ENOMEM;
 
-	if (WARN_ON(insize > sizeof(args.data)))
-		return -EINVAL;
-	memcpy(&args.data[0], buffer, insize);
+	input.length = bios_args_size;
+	input.pointer = args;
 
-	wmi_evaluate_method(HPWMI_BIOS_GUID, 0, mid, &input, &output);
+	mid = encode_outsize_for_pvsz(outsize);
+	if (WARN_ON(mid < 0)) {
+		ret = mid;
+		goto in_free;
+	}
 
-	obj = output.pointer;
+	/* Avoid unnecessary copy to the data buffer if input buffer size is zero */
+	if (insize > 0)
+		memcpy(args->data, buffer, insize);
 
-	if (!obj)
-		return -EINVAL;
+	args->signature = 0x55434553;
+	args->command = command;
+	args->commandtype = query;
+	args->datasize = insize;
 
-	if (obj->type != ACPI_TYPE_BUFFER) {
+	ret = wmi_evaluate_method(HPWMI_BIOS_GUID, 0, mid, &input, &output);
+
+	obj = output.pointer;
+	if (!obj) {
+		pr_warn("query 0x%x returned a null obj 0x%x\n", query, ret);
 		ret = -EINVAL;
-		goto out_free;
+		goto in_free;
 	}
 
-	bios_return = (struct bios_return *)obj->buffer.pointer;
-	ret = bios_return->return_code;
+	if (!ret && obj->type == ACPI_TYPE_BUFFER) {
+		bios_return = (struct bios_return *)obj->buffer.pointer;
+		ret = bios_return->return_code;
+	}
 
 	if (ret) {
 		if (ret != HPWMI_RET_UNKNOWN_COMMAND &&
@@ -299,6 +312,12 @@ static int hp_wmi_perform_query(int query, enum hp_wmi_command command,
 		goto out_free;
 	}
 
+	if (obj->type != ACPI_TYPE_BUFFER) {
+		pr_warn("query 0x%x returned an invalid object 0x%x\n", query, ret);
+		ret = -EINVAL;
+		goto out_free;
+	}
+
 	/* Ignore output data of zero size */
 	if (!outsize)
 		goto out_free;
@@ -309,6 +328,8 @@ static int hp_wmi_perform_query(int query, enum hp_wmi_command command,
 
 out_free:
 	kfree(obj);
+in_free:
+	kfree(args);
 	return ret;
 }
 
-- 
2.25.1