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video: fbdev: via_aux_vt1636: remove VLA usage

PATCH In review Gustavo A. R. Silva 2 participants 2 messages Mar 7, 2018 – Mar 9, 2018

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Framebuffer layer Via unichrome(pro)/CHROME9 framebuffer driver
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Gustavo A. R. Silva

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#0 lore raw

PATCH 1/1 video: fbdev: via_aux_vt1636: remove VLA usage

In preparation to enabling -Wvla, remove VLA and replace it with a fixed-length array instead. Also, remove variable 'len'.

Notice that no new IDs have been added in seven years.

Signed-off-by Gustavo A. R. Silva <[email protected]>
---
 drivers/video/fbdev/via/via_aux_vt1636.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)
drivers/video/fbdev/via/via_aux_vt1636.c +3 -3
index 9e015c1..d6273a4 100644
@@ -35,10 +35,10 @@ void via_aux_vt1636_probe(struct via_aux_bus *bus)
 		.addr	=	0x40,
 		.name	=	name};
 	/* check vendor id and device id */
-	const u8 id[] = {0x06, 0x11, 0x45, 0x33}, len = ARRAY_SIZE(id);
-	u8 tmp[len];
+	const u8 id[4] = {0x06, 0x11, 0x45, 0x33};
+	u8 tmp[4];
 
-	if (!via_aux_read(&drv, 0x00, tmp, len) || memcmp(id, tmp, len))
+	if (!via_aux_read(&drv, 0x00, tmp, 4) || memcmp(id, tmp, 4))
 		return;
 
 	printk(KERN_INFO "viafb: Found %s\n", name);
Signature · 1 line
2.7.4
#1 lore raw
Quoted 15 lines · Gustavo A. R. Silva

In preparation to enabling -Wvla, remove VLA and replace it with a fixed-length array instead. Also, remove variable 'len'.

Notice that no new IDs have been added in seven years.

Signed-off-by Gustavo A. R. Silva <[email protected]>
---
 drivers/video/fbdev/via/via_aux_vt1636.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)
drivers/video/fbdev/via/via_aux_vt1636.c +0 -0
index 9e015c1..d6273a4 100644

drivers/video/fbdev/via/via_aux_vt1636.c void via_aux_vt1636_probe(struct via_aux_bus *bus) · line 41

Quoted 10 lines
drivers/video/fbdev/via/via_aux_vt1636.c +3 -3
@@ -35,10 +35,10 @@ void via_aux_vt1636_probe(struct via_aux_bus *bus)
 		.addr	=	0x40,
 		.name	=	name};
 	/* check vendor id and device id */
-	const u8 id[] = {0x06, 0x11, 0x45, 0x33}, len = ARRAY_SIZE(id);
-	u8 tmp[len];
+	const u8 id[4] = {0x06, 0x11, 0x45, 0x33};
+	u8 tmp[4];
 
-	if (!via_aux_read(&drv, 0x00, tmp, len) || memcmp(id, tmp, len))
+	if (!via_aux_read(&drv, 0x00, tmp, 4) || memcmp(id, tmp, 4))

I would recommend keeping ARRAY_SIZE(); even if nothing's been added in a while, it's still clearer in the code if we can see where these 4 come from.

Something like this instead?
----8<----
@@ -35,10 +35,10 @@ void via_aux_vt1636_probe(struct via_aux_bus *bus)
.addr = 0x40,
.name = name};
/* check vendor id and device id */
- const u8 id[] = {0x06, 0x11, 0x45, 0x33}, len = ARRAY_SIZE(id);
- u8 tmp[len];
+ const u8 id[] = {0x06, 0x11, 0x45, 0x33};
+ u8 tmp[ARRAY_SIZE(id)];

- if (!via_aux_read(&drv, 0x00, tmp, len) || memcmp(id, tmp, len))
+ if (!via_aux_read(&drv, 0x00, tmp, ARRAY_SIZE(id)) || memcmp(id, tmp, ARRAY_SIZE(id)))
return;

printk(KERN_INFO "viafb: Found %s\n", name);
---->8----

Note that sizeof is evaluated a compile time, so u8 tmp[ARRAY_SIZE(id)] is *not* a VLA. All that's needed was to remove len :)

Quoted 10 lines
drivers/video/fbdev/via/via_aux_vt1636.c +0 -0
 		return;
 
 	printk(KERN_INFO "viafb: Found %s\n", name);
Signature · 6 lines
2.7.4

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