From mboxrd@z Thu Jan 1 00:00:00 1970 From: =?UTF-8?B?UmFmYcWCIE1pxYJlY2tp?= Date: Wed, 11 May 2011 18:34:40 +0200 Subject: Optimization: keeping pointer all the time, or defining getter? In-Reply-To: <1305131265.16850.6.camel@maggie> References: <1305131265.16850.6.camel@maggie> Message-ID: List-Id: MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: =?UTF-8?Q?Michael_B=C3=BCsch?= Cc: b43-dev , linux-wireless@vger.kernel.org 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". But if we assume there is some not frequently used struct. What solution should be used then? -- Rafa?