V4L/DVB (5517): Usbvision: store the device database more efficiently

One bit wide bitfields need to declared unsigned to have the range 0 to
1, or they have the range -1 to 0.

A few techniques to reduce the driver's size by about 1700 bytes on ia32,
probably more on x86-64.

Put the biggest fields first, less padding is necessary that way.

Put fields with a limited range into a smaller type.  For example
VideoChannels will fit in 3 bits, and TunerType can use 8 bits.

Vin_Reg1, Vin_Reg2, and Dvi_yuv define values for 8-bit registers, but
they can't just go into an 8-bit field with no changes, since -1 was used
as a flag to indicate a value was not present.  So what we do is create a
one-bit flag for each one to indicate if a value is or is not present.

This only takes 9 bits and has the added advantage that when the register
isn't overridden (Vin_Reg[12] never are) it doesn't need to appear in the
structure definition since the default value for the flag will be zero.

Signed-off-by: Trent Piepho <xyzzy@speakeasy.org>
Acked-by: Thierry MERLE <thierry.merle@free.fr>
Signed-off-by: Mauro Carvalho Chehab <mchehab@infradead.org>

1 files changed, 17 insertions, 14 deletions

diff --git a/drivers/media/video/usbvision/usbvision.h b/drivers/media/video/usbvision/usbvision.h
index b4412a5014ad..9cad77733400 100644
--- a/drivers/media/video/usbvision/usbvision.h
+++ b/drivers/media/video/usbvision/usbvision.h
@@ -342,21 +342,24 @@ struct usbvision_frame {
 #define BRIDGE_NT1005   1005
 
 struct usbvision_device_data_st {
-        int Interface; /* to handle special interface number like BELKIN and Hauppauge WinTV-USB II */
-        int Codec;
-        int VideoChannels;
         __u64 VideoNorm;
-        int AudioChannels;
-        int Radio:1;
-        int vbi:1;
-        int Tuner:1;
-        int TunerType;
-        int Vin_Reg1;
-        int Vin_Reg2;
-        int X_Offset;
-        int Y_Offset;
-        int Dvi_yuv;
-        char *ModelString;
+        const char *ModelString;
+        int Interface; /* to handle special interface number like BELKIN and Hauppauge WinTV-USB II */
+        __u16 Codec;
+        unsigned VideoChannels:3;
+        unsigned AudioChannels:2;
+        unsigned Radio:1;
+        unsigned vbi:1;
+        unsigned Tuner:1;
+        unsigned Vin_Reg1_override:1;   /* Override default value with */
+        unsigned Vin_Reg2_override:1;   /* Vin_Reg1, Vin_Reg2, etc. */
+        unsigned Dvi_yuv_override:1;
+        __u8 Vin_Reg1;
+        __u8 Vin_Reg2;
+        __u8 Dvi_yuv;
+        __u8 TunerType;
+        __s16 X_Offset;
+        __s16 Y_Offset;
 };
 
 /* Declared on usbvision-cards.c */