From mboxrd@z Thu Jan 1 00:00:00 1970 X-GM-THRID: 6667626897637113856 X-Received: by 2002:ac8:4355:: with SMTP id a21mr3681715qtn.9.1552428523108; Tue, 12 Mar 2019 15:08:43 -0700 (PDT) X-BeenThere: outreachy-kernel@googlegroups.com Received: by 2002:a37:6b82:: with SMTP id g124ls1241420qkc.3.gmail; Tue, 12 Mar 2019 15:08:42 -0700 (PDT) X-Google-Smtp-Source: APXvYqw1FLHDtTlRGM60Lkk7ztNzoXaYvLJaxZIJRCpG4nn24XHAKFPPIgaat8bhOl/V/3QvZbwc X-Received: by 2002:ae9:e508:: with SMTP id w8mr4843099qkf.49.1552428522392; Tue, 12 Mar 2019 15:08:42 -0700 (PDT) ARC-Seal: i=1; a=rsa-sha256; t=1552428522; cv=none; d=google.com; s=arc-20160816; b=XT6PkO9kjd93DH4QHN72pLJznubDZTdCZc/CHkThz0IHC6H7m7vH4dwjP3q+k32I3N JGfgQec/LNltcgmdewp17Eb9em/jU/v4El5eG8FahL3VGrE0O7e5Ncy0s6hlu08ogG/N TPckopA6SEVlPLPXVICsqLBxQQ9KGpAgbOJRydHwAqYuN7xEqr21Bw5+mAtj1+7RMRgF k95nJQnLGlB/lr9DaMGSpeblehwBMHX68Mw0DCcNlVvhtpwyMyBlN/co88ldWKRt6dzX kwpeI+1C4+7I5Zi+/2pH5/L/9WUtzS4KJiJAGzr210qYAFrYwYbLVwxG4tuuXRknAgvN fV0Q== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=arc-20160816; h=user-agent:in-reply-to:content-disposition:mime-version:references :message-id:subject:cc:to:from:date:dkim-signature; bh=00DWu19GU3Wnavn6x9yEXNIjxU7KIlaocSoz1HInn7M=; b=R/Cbr7OEmjkz3uudtLgHUEKysOhu6y57bpda8HGXwReEi7N6uLw2v9GvAYfrZIDZ1L /5wcoLhRvQuFhyJAlcrXZW+RovSniiSba87UxBPJ9WexKlOTm5/uMZUQ/wXTAUHNkVX8 /iBxIKUYjXXyPB1khUPPOdPYflcg9UKRgs0EzZpmNzBpHmHeOp7ChSh1zWnklwkRPbip noyHLScwRA/keNxGrJ4zwKl2Q02eobZswJc13aQQlFlP901z6InHDwVqlwuDnuA2GMZQ dG5KdYjHb8GDbT08ht9nXfyMeoGqj8OWD6i9rLNZCAh+l2ogTd5u7G76oeyfYIz6IzmA +2sA== ARC-Authentication-Results: i=1; gmr-mx.google.com; dkim=pass header.i=@kernel.org header.s=default header.b=Rm3Erxxd; spf=pass (google.com: domain of gregkh@linuxfoundation.org designates 198.145.29.99 as permitted sender) smtp.mailfrom=gregkh@linuxfoundation.org Return-Path: Received: from mail.kernel.org (mail.kernel.org. [198.145.29.99]) by gmr-mx.google.com with ESMTPS id v2si487838qka.0.2019.03.12.15.08.42 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Tue, 12 Mar 2019 15:08:42 -0700 (PDT) Received-SPF: pass (google.com: domain of gregkh@linuxfoundation.org designates 198.145.29.99 as permitted sender) client-ip=198.145.29.99; Authentication-Results: gmr-mx.google.com; dkim=pass header.i=@kernel.org header.s=default header.b=Rm3Erxxd; spf=pass (google.com: domain of gregkh@linuxfoundation.org designates 198.145.29.99 as permitted sender) smtp.mailfrom=gregkh@linuxfoundation.org Received: from localhost (unknown [104.133.8.98]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 4FD2A2175B; Tue, 12 Mar 2019 22:08:41 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1552428521; bh=7wmcvanD4LSiOgpiV5KMW3ziVdGamYCdxewiBlFqBKg=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=Rm3ErxxdXyO7E3HwMPr2aW2Ourt9QBso8QHOtX4mrRBiboStp/mG7apvmuergO5LX NO9APcTVRMIe7P+QYxpfIvVZCMyfNkD7+Xjq9GyWPg77XmjW7tdpCqaHztpdMQZWV8 pdPqJVutZZoOyn7ep65U/EK3vsbnxnBlTBGxrkdw= Date: Tue, 12 Mar 2019 15:08:40 -0700 From: Greg KH To: Madhumitha Prabakaran Cc: sudipm.mukherjee@gmail.com, teddy.wang@siliconmotion.com, outreachy-kernel@googlegroups.com Subject: Re: [Outreachy kernel] Re: [PATCH] Staging: sm750fb: Remove unnecessary local variables Message-ID: <20190312220840.GA17773@kroah.com> References: <20190312215737.29200-1-madhumithabiw@gmail.com> <20190312220320.GA17305@kroah.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190312220320.GA17305@kroah.com> User-Agent: Mutt/1.11.3 (2019-02-01) On Tue, Mar 12, 2019 at 03:03:20PM -0700, Greg KH wrote: > On Tue, Mar 12, 2019 at 04:57:37PM -0500, Madhumitha Prabakaran wrote: > > Remove unnecessary local variables in function get_mxclk_freq. > > Issue found by Coccinelle using ret.cocci. > > > > Signed-off-by: Madhumitha Prabakaran > > --- > > drivers/staging/sm750fb/ddk750_chip.c | 17 +++++++---------- > > 1 file changed, 7 insertions(+), 10 deletions(-) > > > > diff --git a/drivers/staging/sm750fb/ddk750_chip.c b/drivers/staging/sm750fb/ddk750_chip.c > > index 90f5480304f4..d0462f21fe36 100644 > > --- a/drivers/staging/sm750fb/ddk750_chip.c > > +++ b/drivers/staging/sm750fb/ddk750_chip.c > > @@ -33,19 +33,16 @@ void sm750_set_chip_type(unsigned short dev_id, u8 rev_id) > > > > static unsigned int get_mxclk_freq(void) > > { > > - unsigned int pll_reg; > > - unsigned int M, N, OD, POD; > > - > > if (sm750_get_chip_type() == SM750LE) > > return MHz(130); > > > > - pll_reg = peek32(MXCLK_PLL_CTRL); > > - M = (pll_reg & PLL_CTRL_M_MASK) >> PLL_CTRL_M_SHIFT; > > - N = (pll_reg & PLL_CTRL_N_MASK) >> PLL_CTRL_N_SHIFT; > > - OD = (pll_reg & PLL_CTRL_OD_MASK) >> PLL_CTRL_OD_SHIFT; > > - POD = (pll_reg & PLL_CTRL_POD_MASK) >> PLL_CTRL_POD_SHIFT; > > - > > - return DEFAULT_INPUT_CLOCK * M / N / (1 << OD) / (1 << POD); > > + return DEFAULT_INPUT_CLOCK * (peek32(MXCLK_PLL_CTRL) & > > + PLL_CTRL_M_MASK) >> PLL_CTRL_M_SHIFT / > > + (peek32(MXCLK_PLL_CTRL) & PLL_CTRL_N_MASK) >> > > + PLL_CTRL_N_SHIFT / (1 << (peek32(MXCLK_PLL_CTRL) & > > + PLL_CTRL_OD_MASK) >> PLL_CTRL_OD_SHIFT) / (1 << > > + (peek32(MXCLK_PLL_CTRL) & PLL_CTRL_POD_MASK) >> > > + PLL_CTRL_POD_SHIFT); > > Oh wow, that's almost impossible to now read. > > Sometimes you want intermediate variables for the programmer, not for > the compiler. The end result is the same, but please tell me that you > could figure out what that one single return line actually does :( > > Remember, we write C code for people to understand first, and the CPU to > understand second as we have to maintain it for the future. Also, this change might be wrong, and at the least, will be slower as you now call peek() a lot more times. Is that a function that has no side-affects on the hardware? At the least it is doing a device access, so you only want to do that once if possible. Remember, there is real hardware behind the driver, that's why the driver is written in the first place :) thanks, greg k-h