On Mon, Feb 15, 2021 at 10:54 AM Leon Romanovsky <leon@xxxxxxxxxx> wrote: > > On Mon, Feb 15, 2021 at 09:23:32AM -0800, Xie He wrote: > > On Mon, Feb 15, 2021 at 1:25 AM Leon Romanovsky <leon@xxxxxxxxxx> 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; I think this is unnecessary. The current comment already explains the meaning of the "1" and the "3". There's no need for a reader of this code to understand what a "2" is. That is the job of the compiler, not the human reader.
