linux-kernel - [PATCH v7 2/6] software node: allow embedding of small arrays into property

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Date:   Thu,  7 Nov 2019 16:17:59 -0800
From:   Dmitry Torokhov <dmitry.torokhov@...il.com>
To:     "Rafael J. Wysocki" <rafael@...nel.org>,
        Heikki Krogerus <heikki.krogerus@...ux.intel.com>
Cc:     Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        Mika Westerberg <mika.westerberg@...ux.intel.com>,
        Linus Walleij <linus.walleij@...aro.org>,
        Ard Biesheuvel <ard.biesheuvel@...aro.org>,
        linux-acpi@...r.kernel.org, linux-kernel@...r.kernel.org,
        platform-driver-x86@...r.kernel.org
Subject: [PATCH v7 2/6] software node: allow embedding of small arrays into property_entry

We should not conflate whether a property data is an array or a single
value with where it is stored (embedded into property_entry structure or
out-of-line). All single-value properties are in effect 1-element
arrays, and we can figure the amount of data stored in a property by
examining its length and the data type. And arrays can be as easily
stored in property entry instances as single values are, provided that
we have enough space (we have up to 8 bytes). We can embed:

- up to 8 bytes from U8 arrays
- up to 4 words
- up to 2 double words
- one U64 value
- one (on 64 bit architectures) or 2 (on 32 bit) strings.

This change also has an effect of switching properties with small amount
of data to embed it instead of keeping it separate when copying such
properties.

Signed-off-by: Dmitry Torokhov <dmitry.torokhov@...il.com>
---
 drivers/base/swnode.c | 103 +++++++++++++++++++-----------------------
 1 file changed, 47 insertions(+), 56 deletions(-)

diff --git a/drivers/base/swnode.c b/drivers/base/swnode.c
index 18a30fb3cc588..ce7f202b2455e 100644
--- a/drivers/base/swnode.c
+++ b/drivers/base/swnode.c
@@ -198,93 +198,84 @@ static int property_entry_read_string_array(const struct property_entry *props,
 
 static void property_entry_free_data(const struct property_entry *p)
 {
-	const void *pointer = property_get_pointer(p);
 	const char * const *src_str;
 	size_t i, nval;
 
-	if (!p->is_inline) {
-		if (p->type == DEV_PROP_STRING && p->pointer) {
-			src_str = p->pointer;
-			nval = p->length / sizeof(const char *);
-			for (i = 0; i < nval; i++)
-				kfree(src_str[i]);
-		}
-		kfree(pointer);
-	} else if (p->type == DEV_PROP_STRING) {
-		kfree(p->value.str);
+	if (p->type == DEV_PROP_STRING) {
+		src_str = property_get_pointer(p);
+		nval = p->length / sizeof(*src_str);
+		for (i = 0; i < nval; i++)
+			kfree(src_str[i]);
 	}
+
+	if (!p->is_inline)
+		kfree(p->pointer);
+
 	kfree(p->name);
 }
 
-static const char * const *
-property_copy_string_array(const struct property_entry *src)
+static bool property_copy_string_array(const char **dst_ptr,
+				       const char * const *src_ptr,
+				       size_t nval)
 {
-	const char **d;
-	const char * const *src_str = src->pointer;
-	size_t nval = src->length / sizeof(*d);
 	int i;
 
-	d = kcalloc(nval, sizeof(*d), GFP_KERNEL);
-	if (!d)
-		return NULL;
-
 	for (i = 0; i < nval; i++) {
-		d[i] = kstrdup(src_str[i], GFP_KERNEL);
-		if (!d[i] && src_str[i]) {
+		dst_ptr[i] = kstrdup(src_ptr[i], GFP_KERNEL);
+		if (!dst_ptr[i] && src_ptr[i]) {
 			while (--i >= 0)
-				kfree(d[i]);
-			kfree(d);
-			return NULL;
+				kfree(dst_ptr[i]);
+			return false;
 		}
 	}
 
-	return d;
+	return true;
 }
 
 static int property_entry_copy_data(struct property_entry *dst,
 				    const struct property_entry *src)
 {
 	const void *pointer = property_get_pointer(src);
-	const void *new;
-
-	if (!src->is_inline) {
-		if (!src->length)
-			return -ENODATA;
-
-		if (src->type == DEV_PROP_STRING) {
-			new = property_copy_string_array(src);
-			if (!new)
-				return -ENOMEM;
-		} else {
-			new = kmemdup(pointer, src->length, GFP_KERNEL);
-			if (!new)
-				return -ENOMEM;
-		}
-
-		dst->pointer = new;
-	} else if (src->type == DEV_PROP_STRING) {
-		new = kstrdup(src->value.str, GFP_KERNEL);
-		if (!new && src->value.str)
+	void *dst_ptr;
+	size_t nval;
+
+	/*
+	 * Properties with no data should not be marked as stored
+	 * out of line.
+	 */
+	if (!src->is_inline && !src->length)
+		return -ENODATA;
+
+	if (src->length <= sizeof(dst->value)) {
+		dst_ptr = &dst->value;
+		dst->is_inline = true;
+	} else {
+		dst_ptr = kmalloc(src->length, GFP_KERNEL);
+		if (!dst_ptr)
 			return -ENOMEM;
+		dst->pointer = dst_ptr;
+	}
 
-		dst->is_inline = true;
-		dst->value.str = new;
+	if (src->type == DEV_PROP_STRING) {
+		nval = src->length / sizeof(const char *);
+		if (!property_copy_string_array(dst_ptr, pointer, nval)) {
+			if (!dst->is_inline)
+				kfree(dst->pointer);
+			return -ENOMEM;
+		}
 	} else {
-		dst->is_inline = true;
-		dst->value = src->value;
+		memcpy(dst_ptr, pointer, src->length);
 	}
 
 	dst->length = src->length;
 	dst->type = src->type;
 	dst->name = kstrdup(src->name, GFP_KERNEL);
-	if (!dst->name)
-		goto out_free_data;
+	if (!dst->name) {
+		property_entry_free_data(dst);
+		return -ENOMEM;
+	}
 
 	return 0;
-
-out_free_data:
-	property_entry_free_data(dst);
-	return -ENOMEM;
 }
 
 /**
-- 
2.24.0.rc1.363.gb1bccd3e3d-goog