On Saturday 9 April 2022 00:21:02 CEST Jaehee Park wrote: > On Fri, Apr 08, 2022 at 11:49:49AM +0200, Julia Lawall wrote: > > On Thu, 7 Apr 2022, Jaehee Park wrote: > > > > > Use container_of() to get vif. This improves the code in two ways: > > > [1] it speeds up the compilation because container_of() saves steps to > > > retrieve vif (the representation of ieee80211_vif), and > > > > I don't understand this part. > > > > julia > > > > Thank you for your message. I revised the commit message (below)-- > I hope it makes it clearer. I'm open to suggestions as well! > > Currently, upon virtual interface creation, wfx_add_interface() stores > a reference to the corresponding struct ieee80211_vif in private data, > for later usage. This is not needed when using the container_of > construct. This construct already has all the info it needs to retrieve > the reference to the corresponding struct from the offset that is > already available, inherent in container_of(), between its type and > member inputs (struct ieee80211_vif and drv_priv, respectively). > Remove vif (which was previously storing the reference to the struct > ieee80211_vif) from the struct wfx_vif, define a macro > wvif_to_vif(wvif) for container_of(), and replace all wvif->vif with > the newly defined container_of construct. > > Sorry if I'm putting out more information than was asked for: > Diagram is worth a thousand words; this one is made by Stefano when > he was explaining the container_of() construct: > > .-----------------------------------. > | .------------------------------. | > '->| struct ieee80211_vif | | > |------------------------------| | > | 1 | | > | 2 | | > | .--------------------------.| | > | 3| struct wfx_vif drv_priv | | > | |---------------------------| | > | | ... | | > | | | | > | | struct ieee80211_vif *vif---' > '------------------------------' > In this example, the offset is 3. > What I want to convey here is the compiler already knows the offset > of drv_priv within struct ieee80211_vif by using the container_of() > construct. So, it doesn't need to do extra work. Wow, nice ascii art :) I think that Julia has not understand why you said it "speeds up the compilation". I think you meant "speeds up the execution", don't you? -- Jérôme Pouiller
