linux-kernel - RE: [PATCH] usb: gadget: f_uac1: Convert use of __constant_cpu_to_le16 to cpu_to

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Date:	Thu, 20 Aug 2015 10:50:45 +0000
From:	David Laight <David.Laight@...LAB.COM>
To:	'Vaishali Thakkar' <vthakkar1994@...il.com>,
	Felipe Balbi <balbi@...com>
CC:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	"linux-usb@...r.kernel.org" <linux-usb@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: RE: [PATCH] usb: gadget: f_uac1: Convert use of
 __constant_cpu_to_le16 to cpu_to_le16

From: Vaishali Thakkar
> Sent: 19 August 2015 06:31
> To: Felipe Balbi
> Cc: Greg Kroah-Hartman; linux-usb@...r.kernel.org; linux-kernel@...r.kernel.org
> Subject: [PATCH] usb: gadget: f_uac1: Convert use of __constant_cpu_to_le16 to cpu_to_le16
> 
> In big endian cases, macro cpu_to_le16 unfolds to __swab16 which
> provides special case for constants. In little endian cases,
> __constant_cpu_to_le16 and cpu_to_le16 expand directly to the
> same expression. So, replace __constant_cpu_to_le16 with
> cpu_to_le16 with the goal of getting rid of the definition of
> __constant_cpu_to_le16 completely.
> 
> The semantic patch that performs this transformation is as follows:
> 
> @@expression x;@@
> 
> - __constant_cpu_to_le16(x)
> + cpu_to_le16(x)
> 
> Signed-off-by: Vaishali Thakkar <vthakkar1994@...il.com>
> ---
>  drivers/usb/gadget/function/f_uac1.c | 6 +++---
>  1 file changed, 3 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/usb/gadget/function/f_uac1.c b/drivers/usb/gadget/function/f_uac1.c
> index 7856b33..5aa8d8a 100644
> --- a/drivers/usb/gadget/function/f_uac1.c
> +++ b/drivers/usb/gadget/function/f_uac1.c
> @@ -57,8 +57,8 @@ static struct uac1_ac_header_descriptor_1 ac_header_desc = {
>  	.bLength =		UAC_DT_AC_HEADER_LENGTH,
>  	.bDescriptorType =	USB_DT_CS_INTERFACE,
>  	.bDescriptorSubtype =	UAC_HEADER,
> -	.bcdADC =		__constant_cpu_to_le16(0x0100),
> -	.wTotalLength =		__constant_cpu_to_le16(UAC_DT_TOTAL_LENGTH),
> +	.bcdADC =		cpu_to_le16(0x0100),
> +	.wTotalLength =		cpu_to_le16(UAC_DT_TOTAL_LENGTH),

Have you test compiled this on a big-endian system?
My gut feeling is that is fails.

	David

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