usb: replace hardcoded maximum usb string length by definition

Commit Message

Macpaul Lin June 12, 2020, 5:32 a.m. UTC

Replace hardcoded maximum usb string length (126 bytes) by definition
"MAX_USB_STRING_LEN".

Signed-off-by: Macpaul Lin <[e-mail]>
---
 drivers/usb/gadget/composite.c |    4 ++--
 drivers/usb/gadget/configfs.c  |    3 ++-
 drivers/usb/gadget/usbstring.c |    5 +++--
 include/linux/usb.h            |    2 ++
 4 files changed, 9 insertions(+), 5 deletions(-)

Comments

Alan Stern June 12, 2020, 2:02 p.m. UTC | #1

On Fri, Jun 12, 2020 at 01:32:47PM +0800, Macpaul Lin wrote:
> Replace hardcoded maximum usb string length (126 bytes) by definition
> "MAX_USB_STRING_LEN".
> 
> Signed-off-by: Macpaul Lin <[e-mail]>

...

> diff --git a/include/linux/usb.h b/include/linux/usb.h
> index 9f3c721..df4a9cb 100644
> --- a/include/linux/usb.h
> +++ b/include/linux/usb.h
> @@ -1815,6 +1815,8 @@ static inline int usb_get_ptm_status(struct usb_device *dev, void *data)
>  		0, data);
>  }
>  
> +/* USB String descriptors can contain at most 126 characters. */
> +#define MAX_USB_STRING_LEN	126

This definition belongs in include/uapi/linux/usb/ch9.h (near the 
definition of struct usb_string_descriptor) because it is part of the USB 
standard rather than specific to the Linux USB stack.

Alan Stern

Patch

diff --git a/drivers/usb/gadget/composite.c b/drivers/usb/gadget/composite.c
index cb4950c..d0de016 100644
--- a/drivers/usb/gadget/composite.c
+++ b/drivers/usb/gadget/composite.c
@@ -1041,7 +1041,7 @@  static void collect_langs(struct usb_gadget_strings **sp, __le16 *buf)
 	while (*sp) {
 		s = *sp;
 		language = cpu_to_le16(s->language);
-		for (tmp = buf; *tmp && tmp < &buf[126]; tmp++) {
+		for (tmp = buf; *tmp && tmp < &buf[MAX_USB_STRING_LEN]; tmp++) {
 			if (*tmp == language)
 				goto repeat;
 		}
@@ -1116,7 +1116,7 @@  static int get_string(struct usb_composite_dev *cdev,
 			collect_langs(sp, s->wData);
 		}
 
-		for (len = 0; len <= 126 && s->wData[len]; len++)
+		for (len = 0; len <= MAX_USB_STRING_LEN && s->wData[len]; len++)
 			continue;
 		if (!len)
 			return -EINVAL;
diff --git a/drivers/usb/gadget/configfs.c b/drivers/usb/gadget/configfs.c
index 32b637e..c9d61ac 100644
--- a/drivers/usb/gadget/configfs.c
+++ b/drivers/usb/gadget/configfs.c
@@ -4,6 +4,7 @@ 
 #include <linux/slab.h>
 #include <linux/device.h>
 #include <linux/nls.h>
+#include <linux/usb.h>
 #include <linux/usb/composite.h>
 #include <linux/usb/gadget_configfs.h>
 #include "configfs.h"
@@ -115,7 +116,7 @@  static int usb_string_copy(const char *s, char **s_copy)
 	char *str;
 	char *copy = *s_copy;
 	ret = strlen(s);
-	if (ret > 126)
+	if (ret > MAX_USB_STRING_LEN)
 		return -EOVERFLOW;
 
 	str = kstrdup(s, GFP_KERNEL);
diff --git a/drivers/usb/gadget/usbstring.c b/drivers/usb/gadget/usbstring.c
index 7c24d1c..c125d59 100644
--- a/drivers/usb/gadget/usbstring.c
+++ b/drivers/usb/gadget/usbstring.c
@@ -11,6 +11,7 @@ 
 #include <linux/device.h>
 #include <linux/nls.h>
 
+#include <linux/usb.h>
 #include <linux/usb/ch9.h>
 #include <linux/usb/gadget.h>
 
@@ -55,9 +56,9 @@ 
 		return -EINVAL;
 
 	/* string descriptors have length, tag, then UTF16-LE text */
-	len = min ((size_t) 126, strlen (s->s));
+	len = min((size_t)MAX_USB_STRING_LEN, strlen(s->s));
 	len = utf8s_to_utf16s(s->s, len, UTF16_LITTLE_ENDIAN,
-			(wchar_t *) &buf[2], 126);
+			(wchar_t *) &buf[2], MAX_USB_STRING_LEN);
 	if (len < 0)
 		return -EINVAL;
 	buf [0] = (len + 1) * 2;
diff --git a/include/linux/usb.h b/include/linux/usb.h
index 9f3c721..df4a9cb 100644
--- a/include/linux/usb.h
+++ b/include/linux/usb.h
@@ -1815,6 +1815,8 @@  static inline int usb_get_ptm_status(struct usb_device *dev, void *data)
 		0, data);
 }
 
+/* USB String descriptors can contain at most 126 characters. */
+#define MAX_USB_STRING_LEN	126
 extern int usb_string(struct usb_device *dev, int index,
 	char *buf, size_t size);