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Tue, 24 Sep 2019 10:03:18 +0000 Received: from DB3PR0402MB3916.eurprd04.prod.outlook.com ([fe80::8958:299c:bc54:2a38]) by DB3PR0402MB3916.eurprd04.prod.outlook.com ([fe80::8958:299c:bc54:2a38%7]) with mapi id 15.20.2284.023; Tue, 24 Sep 2019 10:03:18 +0000 From: Anson Huang To: David Laight , "thierry.reding@gmail.com" , "shawnguo@kernel.org" , "s.hauer@pengutronix.de" , "kernel@pengutronix.de" , "festevam@gmail.com" , "linux-pwm@vger.kernel.org" , "linux-arm-kernel@lists.infradead.org" , "linux-kernel@vger.kernel.org" Subject: RE: [PATCH] pwm: pwm-imx27: Use 'dev' instead of dereferencing it repeatedly Thread-Topic: [PATCH] pwm: pwm-imx27: Use 'dev' instead of dereferencing it repeatedly Thread-Index: AQHVcra4SlIMDowCwkO5fDgX0dE1dKc6lGgAgAADXwA= Date: Tue, 24 Sep 2019 10:03:18 +0000 Message-ID: References: <1569315593-769-1-git-send-email-Anson.Huang@nxp.com> <6cfb1595992b46dc884731555e6f0334@AcuMS.aculab.com> In-Reply-To: <6cfb1595992b46dc884731555e6f0334@AcuMS.aculab.com> Accept-Language: en-US Content-Language: en-US X-MS-Has-Attach: X-MS-TNEF-Correlator: authentication-results: spf=none (sender IP is ) smtp.mailfrom=anson.huang@nxp.com; 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charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+infradead-linux-arm-kernel=archiver.kernel.org@lists.infradead.org Hi, David > Subject: RE: [PATCH] pwm: pwm-imx27: Use 'dev' instead of dereferencing it > repeatedly > > From: Anson Huang > > Sent: 24 September 2019 10:00 > > Add helper variable dev = &pdev->dev to simply the code. > > > > Signed-off-by: Anson Huang > > --- > > drivers/pwm/pwm-imx27.c | 13 +++++++------ > > 1 file changed, 7 insertions(+), 6 deletions(-) > > > > diff --git a/drivers/pwm/pwm-imx27.c b/drivers/pwm/pwm-imx27.c index > > 434a351..3afee29 100644 > > --- a/drivers/pwm/pwm-imx27.c > > +++ b/drivers/pwm/pwm-imx27.c > > @@ -290,27 +290,28 @@ MODULE_DEVICE_TABLE(of, > pwm_imx27_dt_ids); > > > > static int pwm_imx27_probe(struct platform_device *pdev) { > > + struct device *dev = &pdev->dev; > > struct pwm_imx27_chip *imx; > > > > - imx = devm_kzalloc(&pdev->dev, sizeof(*imx), GFP_KERNEL); > > + imx = devm_kzalloc(dev, sizeof(*imx), GFP_KERNEL); > > if (imx == NULL) > > return -ENOMEM; > > > > platform_set_drvdata(pdev, imx); > > > > - imx->clk_ipg = devm_clk_get(&pdev->dev, "ipg"); > > + imx->clk_ipg = devm_clk_get(dev, "ipg"); > > if (IS_ERR(imx->clk_ipg)) { > > - dev_err(&pdev->dev, "getting ipg clock failed with %ld\n", > > + dev_err(dev, "getting ipg clock failed with %ld\n", > > PTR_ERR(imx->clk_ipg)); > > return PTR_ERR(imx->clk_ipg); > > } > > > > - imx->clk_per = devm_clk_get(&pdev->dev, "per"); > > + imx->clk_per = devm_clk_get(dev, "per"); > > if (IS_ERR(imx->clk_per)) { > > int ret = PTR_ERR(imx->clk_per); > > > > if (ret != -EPROBE_DEFER) > > - dev_err(&pdev->dev, > > + dev_err(dev, > > "failed to get peripheral clock: %d\n", > > ret); > > Hopefully the compiler will optimise this back otherwise you've added > another local variable which may cause spilling to stack. > For a setup function it probably doesn't matter, but in general it might have a > small negative performance impact. > > In any case this doesn't shorten any lines enough to remove line-wrap and > using &pdev->dev is really one less variable to mentally track when reading > the code. Do we know which compiler will optimize this? I saw many of the patches doing this to avoid a lot of dereference, I understand it does NOT save lines, but my intention is to avoid dereference which might save some instructions. I thought saving instructions is more important. So now there are different opinion about doing this? Anson _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel