Hi Wolfgang,
On Mon, Jun 6, 2011 at 11:28 PM, Wolfgang Denk wd@denx.de wrote:
Dear Simon Glass,
In message BANLkTimCGQbih16u7772-uKHb0bUyApbe14mNQ91zhqi1SS62w@mail.gmail.com you wrote:
OK I understand, thank you. How about this approach: we could add a new macro to io.h, something like:
#define clrsetfield_le32(bitfield, addr, value) ...
Then caller can define these in a header file:
#define FIELD_MASK 0xf0000 #define FIELD_SHIFT 16
And use this macro to set the bitfield to 6, for example:
clrsetfield_le32(FIELD, &my_device->ctrl, 6)
(this will simply shift the value left 16 bits and apply the supplied mask)
This captures the essence of bitfields, in that we are abstracting the field under a single name. The change would just add this macro to the io.h header file.
Sorry, I fail to understand how you envision to use this, and how it would be different from clrsetbits*() ?
For example this allows us to replace:
clrsetbits_le(&my_device->ctrl, 0xf << 16, 6 << 16)
with:
clrsetfield_le32(FIELD, &my_device->ctrl, 6)
So the two identical shifts are avoided, and the forming of the mask is done once in the define.
Please do try to help me out with a form of bitfield definition that you would be comfortable with. This approach here makes use of clrsetbits*() and extends it in a simple way. If there is another better or more acceptable approach then please do let me know.
Regards, Simon
Best regards,
Wolfgang Denk
-- DENX Software Engineering GmbH, MD: Wolfgang Denk & Detlev Zundel HRB 165235 Munich, Office: Kirchenstr.5, D-82194 Groebenzell, Germany Phone: (+49)-8142-66989-10 Fax: (+49)-8142-66989-80 Email: wd@denx.de No one wants war. -- Kirk, "Errand of Mercy", stardate 3201.7