On Mon, Feb 15, 2021 at 09:23:32AM -0800, Xie He wrote: > On Mon, Feb 15, 2021 at 1:25 AM Leon Romanovsky <l...@kernel.org> wrote: > > > > > + /* When transmitting data: > > > + * first we'll remove a pseudo header of 1 byte, > > > + * then the LAPB module will prepend an LAPB header of at most 3 > > > bytes. > > > + */ > > > + dev->needed_headroom = 3 - 1; > > > > 3 - 1 = 2 > > > > Thanks > > Actually this is intentional. It makes the numbers more meaningful. > > The compiler should automatically generate the "2" so there would be > no runtime penalty.
If you want it intentional, write it in the comment. /* When transmitting data, we will need extra 2 bytes headroom, * which are 3 bytes of LAPB header minus one byte of pseudo header. */ dev->needed_headroom = 2;
