Yes, this is currently documented in the doxygen for the various set headroom routines for the patch I posted last night. >From your code snippet are you suggesting that some platforms have a fixed headroom that cannot be changed? The assumption we've had is that this is settable at least on a per-interface level.
Bill On Tue, Nov 11, 2014 at 12:39 AM, Shmulik Ladkani <[email protected] > wrote: > Hi, > > On Mon, 10 Nov 2014 22:49:25 -0600 Bill Fischofer < > [email protected]> wrote: > > No, the suggestion is that implementations understand that the > application > > assumes buffers are "naturally aligned" so the implementation can infer > the > > requested alignment from the specified headroom request. So for example > if > > the user requests a hr of 10 that means the user expects the packet to be > > offset by two bytes from an 8 byte alignment. The implementation is free > > to add to the requested hr as long as the result preserves the implied > > alignment from the original request. So giving an hr of 18 or 26 is OK. > > OK, this is fine. > > So implementor MUST preserve the implicit offset "hint" provided by > user's headroom value (i.e. allowed to add extra number of headroom > bytes which is a multiple of an agreed alignment factor, preferrably > platform independent factor). > > Meaning, such implementation isn't allowed: > > #define IMPL_MAX_HEADROOM 128 > > if (user_headroom > IMPL_MAX_HEADROOM) > return -ERR_NOT_SUPP; > actual_headroom = IMPL_MAX_HEADROOM; /* XXX: for ease of > implementation */ > > This should be documented. > > Regards, > Shmulik >
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