linux-kernel - Re: [PATCH 01/13] edac: Create a dimm struct and move the labels into it

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Date:	Mon, 16 Apr 2012 13:02:22 +0200
From:	Borislav Petkov <bp@...64.org>
To:	Mauro Carvalho Chehab <mchehab@...hat.com>
Cc:	Borislav Petkov <bp@...64.org>,
	Linux Edac Mailing List <linux-edac@...r.kernel.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 01/13] edac: Create a dimm struct and move the labels
 into it

On Mon, Apr 16, 2012 at 05:41:33AM -0300, Mauro Carvalho Chehab wrote:
> This is not a double loop.

But it is, actually.

Let's look at the code:

        /* setup index and various internal pointers */
        mci->mc_idx = edac_index;
        mci->csrows = csi;
        mci->dimms  = dimm;
        mci->pvt_info = pvt;
        mci->nr_csrows = nr_csrows;

        for (row = 0; row < nr_csrows; row++) {					<-- A1
                csrow = &csi[row];
                csrow->csrow_idx = row;
                csrow->mci = mci;
                csrow->nr_channels = nr_chans;
                chp = &chi[row * nr_chans];
                csrow->channels = chp;

                for (chn = 0; chn < nr_chans; chn++) {				<-- B1
                        chan = &chp[chn];
                        chan->chan_idx = chn;
                        chan->csrow = csrow;
                }
        }

        /*
         * By default, assumes that a per-csrow arrangement will be used,
         * as most drivers are based on such assumption.
         */
        dimm = mci->dimms;
        for (row = 0; row < mci->nr_csrows; row++) {				<-- A2
                for (chn = 0; chn < mci->csrows[row].nr_channels; chn++) {	<-- B2
                        mci->csrows[row].channels[chn].dimm = dimm;
                        dimm->csrow = row;
                        dimm->csrow_channel = chn;
                        dimm++;
                        mci->nr_dimms++;
                }
        }

So the lines tagged with A1 and A2 iterate over the nr_csrows, while
lines tagged with B1 and B2 iterate over nr_chans. In B2, loop termination is

	mci->csrows[row].nr_channels

which is assigned in the first loop above to

	csrow->nr_channels = nr_chans

In B1, it is simply nr_chans.

So how about we merge those two:

	...
	dimm = mci->dimms;

        for (row = 0; row < nr_csrows; row++) {					<-- A1
                csrow = &csi[row];
                csrow->csrow_idx = row;
                csrow->mci = mci;
                csrow->nr_channels = nr_chans;
                chp = &chi[row * nr_chans];
                csrow->channels = chp;

                for (chn = 0; chn < nr_chans; chn++) {				<-- B1
                        chan = &chp[chn];
                        chan->chan_idx = chn;
                        chan->csrow = csrow;

			 /* second loop */
                        csrow->channels[chn].dimm = dimm;
                        dimm->csrow = row;
                        dimm->csrow_channel = chn;
                        dimm++;
                        mci->nr_dimms++;
                }
        }

So it is only 5 lines of code instead of another loop.

-- 
Regards/Gruss,
Boris.

Advanced Micro Devices GmbH
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