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Date: Tue, 28 Feb 2017 12:24:39 +0100 (CET)
From: Julia Lawall <julia.lawall@...6.fr>
To: Joe Perches <joe@...ches.com>
cc: Arushi Singhal <arushisinghal19971997@...il.com>,
arnaud.patard@...-net.org,
Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
devel@...verdev.osuosl.org, linux-kernel@...r.kernel.org,
outreachy-kernel@...glegroups.com
Subject: Re: [Outreachy kernel] Re: [PATCH v7] staging: xgifb: correct the
multiple line dereference
On Tue, 28 Feb 2017, Joe Perches wrote:
> On Tue, 2017-02-28 at 16:15 +0530, Arushi Singhal wrote:
> > Error reported by checkpatch.pl as "avoid multiple line dereference".
> > Addition of new variables to make the code more readable.
>
> You should probably split this into 2 patches, one for
> each file.
>
> What Julia said about finding a better/shorter identifier
> than RefreshRateTableIndex is true but I still suggest
> something like:
>
> > diff --git a/drivers/staging/xgifb/vb_setmode.c b/drivers/staging/xgifb/vb_setmode.c@@ -221,8 +221,8 @@ static unsigned char XGI_AjustCRT2Rate(unsigned short ModeIdIndex,
> >
> > for (; XGI330_RefIndex[RefreshRateTableIndex + (*i)].ModeID ==
> > tempbx; (*i)--) {
> > - infoflag = XGI330_RefIndex[RefreshRateTableIndex + (*i)].
> > - Ext_InfoFlag;
> > + infoflag = XGI330_RefIndex[RefreshRateTableIndex + (*i)].Ext_InfoFlag;
> > +
>
> I suggest something like:
> ---
> drivers/staging/xgifb/vb_setmode.c | 41 ++++++++++++++++++--------------------
> 1 file changed, 19 insertions(+), 22 deletions(-)
>
> diff --git a/drivers/staging/xgifb/vb_setmode.c b/drivers/staging/xgifb/vb_setmode.c
> index 7c7c8c8f1df3..daa3318aab41 100644
> --- a/drivers/staging/xgifb/vb_setmode.c
> +++ b/drivers/staging/xgifb/vb_setmode.c
> @@ -172,10 +172,12 @@ static unsigned char XGI_AjustCRT2Rate(unsigned short ModeIdIndex,
> struct vb_device_info *pVBInfo)
> {
> unsigned short tempax, tempbx, resinfo, modeflag, infoflag;
> + const struct XGI_Ext2Struct *ext2;
>
> modeflag = XGI330_EModeIDTable[ModeIdIndex].Ext_ModeFlag;
> resinfo = XGI330_EModeIDTable[ModeIdIndex].Ext_RESINFO;
> - tempbx = XGI330_RefIndex[RefreshRateTableIndex + (*i)].ModeID;
> + ext2 = &XGI330_RefIndex[RefreshRateTableIndex];
> + tempbx = ext2[*i].ModeID;
> tempax = 0;
>
> if (pVBInfo->VBInfo & SetCRT2ToRAMDAC) {
> @@ -219,10 +221,8 @@ static unsigned char XGI_AjustCRT2Rate(unsigned short ModeIdIndex,
> return 0;
> }
>
> - for (; XGI330_RefIndex[RefreshRateTableIndex + (*i)].ModeID ==
> - tempbx; (*i)--) {
> - infoflag = XGI330_RefIndex[RefreshRateTableIndex + (*i)].
> - Ext_InfoFlag;
> + for (; ext2[*i].ModeID == tempbx; (*i)--) {
> + infoflag = ext2[*i].Ext_InfoFlag;
> if (infoflag & tempax)
> return 1;
>
> @@ -231,12 +231,9 @@ static unsigned char XGI_AjustCRT2Rate(unsigned short ModeIdIndex,
> }
>
> for ((*i) = 0;; (*i)++) {
> - infoflag = XGI330_RefIndex[RefreshRateTableIndex + (*i)].
> - Ext_InfoFlag;
> - if (XGI330_RefIndex[RefreshRateTableIndex + (*i)].ModeID
> - != tempbx) {
> + infoflag = ext2[*i].Ext_InfoFlag;
> + if (ext2[*i].ModeID != tempbx)
> return 0;
> - }
It's drifting a little bit from the original issue, but the whole *i thing
is not very nice. The function is used in only one place, and the call
looks like this:
temp = XGI_AjustCRT2Rate(ModeIdIndex, RefreshRateTableIndex,
&i, pVBInfo);
immediately followed by:
return RefreshRateTableIndex + i;
temp is never used. Could the function be made to return a negative error
code on failure and the updated value of i on success? The (*i) could
become just i, which would even be a little shorter.
julia
>
> if (infoflag & tempax)
> return 1;
> @@ -5050,6 +5047,7 @@ unsigned short XGI_GetRatePtrCRT2(struct xgi_hw_device_info *pXGIHWDE,
> {
> const u8 LCDARefreshIndex[] = {
> 0x00, 0x00, 0x03, 0x01, 0x01, 0x01, 0x01, 0x00 };
> + const struct XGI_Ext2Struct *ext2;
>
> unsigned short RefreshRateTableIndex, i, index, temp;
>
> @@ -5073,29 +5071,29 @@ unsigned short XGI_GetRatePtrCRT2(struct xgi_hw_device_info *pXGIHWDE,
> }
>
> RefreshRateTableIndex = XGI330_EModeIDTable[ModeIdIndex].REFindex;
> - ModeNo = XGI330_RefIndex[RefreshRateTableIndex].ModeID;
> + ext2 = &XGI330_RefIndex[RefreshRateTableIndex];
> + ModeNo = ext2->ModeID;
> if (pXGIHWDE->jChipType >= XG20) { /* for XG20, XG21, XG27 */
> - if ((XGI330_RefIndex[RefreshRateTableIndex].XRes == 800) &&
> - (XGI330_RefIndex[RefreshRateTableIndex].YRes == 600)) {
> + if ((ext2->XRes == 800) &&
> + (ext2->YRes == 600)) {
> index++;
> }
> /* do the similar adjustment like XGISearchCRT1Rate() */
> - if ((XGI330_RefIndex[RefreshRateTableIndex].XRes == 1024) &&
> - (XGI330_RefIndex[RefreshRateTableIndex].YRes == 768)) {
> + if ((ext2->XRes == 1024) &&
> + (ext2->YRes == 768)) {
> index++;
> }
> - if ((XGI330_RefIndex[RefreshRateTableIndex].XRes == 1280) &&
> - (XGI330_RefIndex[RefreshRateTableIndex].YRes == 1024)) {
> + if ((ext2->XRes == 1280) &&
> + (ext2->YRes == 1024)) {
> index++;
> }
> }
>
> i = 0;
> do {
> - if (XGI330_RefIndex[RefreshRateTableIndex + i].
> - ModeID != ModeNo)
> + if (ext2[i].ModeID != ModeNo)
> break;
> - temp = XGI330_RefIndex[RefreshRateTableIndex + i].Ext_InfoFlag;
> + temp = ext2[i].Ext_InfoFlag;
> temp &= ModeTypeMask;
> if (temp < pVBInfo->ModeType)
> break;
> @@ -5105,8 +5103,7 @@ unsigned short XGI_GetRatePtrCRT2(struct xgi_hw_device_info *pXGIHWDE,
> } while (index != 0xFFFF);
> if (!(pVBInfo->VBInfo & SetCRT2ToRAMDAC)) {
> if (pVBInfo->VBInfo & SetInSlaveMode) {
> - temp = XGI330_RefIndex[RefreshRateTableIndex + i - 1].
> - Ext_InfoFlag;
> + temp = ext2[i - 1].Ext_InfoFlag;
> if (temp & InterlaceMode)
> i++;
> }
>
> --
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