From mboxrd@z Thu Jan 1 00:00:00 1970 From: Michael =?ISO-8859-1?Q?B=FCsch?= Date: Wed, 11 May 2011 18:27:45 +0200 Subject: Optimization: keeping pointer all the time, or defining getter? In-Reply-To: References: Message-ID: <1305131265.16850.6.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 18:22 +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. -- Greetings Michael.