| commit | c682b3a7fb8ec69ac73511bbb6a378e40aa35f35 | |
| author | Trent Piepho <xyzzy@speakeasy.org> | |
| Sat, 14 Apr 2007 18:16:26 +0000 (14 15:16 -0300) | ||
| committer | Mauro Carvalho Chehab <mchehab@infradead.org> | |
| Fri, 27 Apr 2007 18:45:34 +0000 (27 15:45 -0300) | ||
| tree | 443ac5b210222822c3f4883964defd2404601d7a | treesnapshot (tar.gz zip) |
| parent | f7ca6256bc1db4fb44adda99e082f8c80ada8957 | commitdiff |
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>
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>