From mboxrd@z Thu Jan 1 00:00:00 1970 From: Michael =?ISO-8859-1?Q?B=FCsch?= Date: Wed, 11 May 2011 18:43:10 +0200 Subject: Optimization: keeping pointer all the time, or defining getter? In-Reply-To: References: <1305131265.16850.6.camel@maggie> Message-ID: <1305132190.16850.7.camel@maggie> List-Id: MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: =?UTF-8?Q?Rafa=C5=82_Mi=C5=82ecki?= Cc: b43-dev , linux-wireless@vger.kernel.org On Wed, 2011-05-11 at 18:34 +0200, Rafa? Mi?ecki wrote: > W dniu 11 maja 2011 18:27 u?ytkownik Michael B?sch napisa?: > > On Wed, 2011-05-11 at 18:22 +0200, Rafa? Mi?ecki wrote: > >> I try to abstract bus in b43 driver. For frequently used fields > >> solution is obvious: > >> At init time I get info from bus-specific stuct and put it in generic field. > >> Example: core revision. We often refer to it, I put it in abstraction struct. > >> > >> My question: what is the policy for cases with less frequently used fields? > >> Example: I need to use "struct device" for registering some low lever stuff. > >> > >> I have two solutions: > >> > >> 1) Realtime: > >> struct device *get_device(...) > >> { > >> if (dev->bus_type = B43_BUS_SSB) > >> return dev->ssbdev->device; > >> else if (dev->bus_type = B43_BUS_BCMA) > >> return dev->bcmadev->device; > >> } > >> > >> 2) Init time: > >> void b43_ssb_init(struct ssb_device *ssbdev) > >> { > >> dev->struct = ssbdev->device; > >> } > >> > >> The first one is slower but we don't keep "struct device" pointer in > >> abstraction struct. Situation is opposite for the second one. > >> > >> Does anyone care? ;) > > > > Put a struct device pointer into b43_wldev. > > The pointer is needed on every DMA transaction several times, so this > > seems worth it. > > Oops, OK, that was example. I thought DMA uses "dma_dev" frequently, not "dev". Ah well. I don't know. Isn't dma_dev part of some SSB struct? > But if we assume there is some not frequently used struct. What > solution should be used then? Apply common sense. ;) -- Greetings Michael.