From 7c0143153cd33a0a267908ca419e2adc40ee513a Mon Sep 17 00:00:00 2001 From: Mathias Nyman Date: Tue, 19 Dec 2017 13:28:30 +0200 Subject: [PATCH] USB: clarify USB_DT_USB_SSP_CAP_SIZE(ssac) definition USB_DT_USB_SSP_CAP_SIZE(ssac) gives the size of the SSP capability descriptor. The descriptor consists of 12 bytes plus a array of SSA entries. The number of SSA entries is stored in a SSAC value in the first 12 bytes, The USB3.1 specification 9.6.2.5 defines SSAC as zero based: "The number of Sublink Speed Attributes = SSAC + 1." This is not intuitive and has already caused some confusion. Make a small modifiaction to the USB_DT_USB_SSP_CAP_SIZE(ssac) definition to make it a bit clearer Signed-off-by: Mathias Nyman Signed-off-by: Greg Kroah-Hartman --- include/uapi/linux/usb/ch9.h | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/include/uapi/linux/usb/ch9.h b/include/uapi/linux/usb/ch9.h index c4c79aa3..d5a5cae 100644 --- a/include/uapi/linux/usb/ch9.h +++ b/include/uapi/linux/usb/ch9.h @@ -1077,9 +1077,9 @@ struct usb_ptm_cap_descriptor { #define USB_DT_USB_PTM_ID_SIZE 3 /* * The size of the descriptor for the Sublink Speed Attribute Count - * (SSAC) specified in bmAttributes[4:0]. + * (SSAC) specified in bmAttributes[4:0]. SSAC is zero-based */ -#define USB_DT_USB_SSP_CAP_SIZE(ssac) (16 + ssac * 4) +#define USB_DT_USB_SSP_CAP_SIZE(ssac) (12 + (ssac + 1) * 4) /*-------------------------------------------------------------------------*/ -- 2.7.4