[PATCH RESEND] usbtty: fix possible alignment issues

[Tom Rini]

On Tue, Jan 07, 2020 at 02:25:02PM +0900, Seung-Woo Kim wrote:

> With gcc9, below warnings are shown:
>   drivers/serial/usbtty.c: In function 'usbtty_init_strings':
>   drivers/serial/usbtty.c:590:44: warning: taking address of packed member of 'struct usb_string_descriptor' may result in an unaligned pointer value [-Waddress-of-packed-member]
>     590 |  str2wide (CONFIG_USBD_MANUFACTURER, string->wData);
>         |                                      ~~~~~~^~~~~~~
>   drivers/serial/usbtty.c:596:44: warning: taking address of packed member of 'struct usb_string_descriptor' may result in an unaligned pointer value [-Waddress-of-packed-member]
>     597 |  str2wide (CONFIG_USBD_PRODUCT_NAME, string->wData);
>         |                                      ~~~~~~^~~~~~~
>   drivers/serial/usbtty.c:603:33: warning: taking address of packed member of 'struct usb_string_descriptor' may result in an unaligned pointer value [-Waddress-of-packed-member]
>     604 |  str2wide (serial_number, string->wData);
>         |                           ~~~~~~^~~~~~~
>   drivers/serial/usbtty.c:610:49: warning: taking address of packed member of 'struct usb_string_descriptor' may result in an unaligned pointer value [-Waddress-of-packed-member]
>     611 |  str2wide (CONFIG_USBD_CONFIGURATION_STR, string->wData);
>         |                                           ~~~~~~^~~~~~~
>   drivers/serial/usbtty.c:617:50: warning: taking address of packed member of 'struct usb_string_descriptor' may result in an unaligned pointer value [-Waddress-of-packed-member]
>     618 |  str2wide (CONFIG_USBD_DATA_INTERFACE_STR, string->wData);
>         |                                            ~~~~~~^~~~~~~
>   drivers/serial/usbtty.c:623:50: warning: taking address of packed member of 'struct usb_string_descriptor' may result in an unaligned pointer value [-Waddress-of-packed-member]
>     624 |  str2wide (CONFIG_USBD_CTRL_INTERFACE_STR, string->wData);
>         |                                            ~~~~~~^~~~~~~
> 
> Fix the issues by using packed structure.
> 
> Ref: commit 616ebd8b9cb4 ("usb: composite: fix possible alignment issues")
> Signed-off-by: Seung-Woo Kim <sw0312.kim at samsung.com>
> ---
> resend with proper e-mail address
> ---
>  drivers/serial/usbtty.c | 9 ++++++---
>  1 file changed, 6 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/serial/usbtty.c b/drivers/serial/usbtty.c
> index f1c1a260da..54e67dd0d1 100644
> --- a/drivers/serial/usbtty.c
> +++ b/drivers/serial/usbtty.c
> @@ -48,6 +48,8 @@
>  #define CONFIG_USBD_DATA_INTERFACE_STR "Bulk Data Interface"
>  #define CONFIG_USBD_CTRL_INTERFACE_STR "Control Interface"
>  
> +typedef struct { __le16 val; } __attribute__((aligned(16))) __le16_packed;
> +
>  /*
>   * Buffers to hold input and output data
>   */
> @@ -372,14 +374,15 @@ static int fill_buffer (circbuf_t * buf);
>  void usbtty_poll (void);
>  
>  /* utility function for converting char* to wide string used by USB */
> -static void str2wide (char *str, u16 * wide)
> +static void str2wide (char *str, void *wide)
>  {
>  	int i;
> +	__le16_packed	*tmp = wide;
>  	for (i = 0; i < strlen (str) && str[i]; i++){
>  		#if defined(__LITTLE_ENDIAN)
> -			wide[i] = (u16) str[i];
> +			tmp[i].val = (u16) str[i];
>  		#elif defined(__BIG_ENDIAN)
> -			wide[i] = ((u16)(str[i])<<8);
> +			tmp[i].val = ((u16)(str[i])<<8);
>  		#else
>  			#error "__LITTLE_ENDIAN or __BIG_ENDIAN undefined"
>  		#endif

We generally don't want packed structs and do need to disable this
warning in general.  Is this _really_ a problem, or are we just
silencing the compiler here?  Thanks!

-- 
Tom
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