lkml.org 
[lkml]   [2002]   [May]   [15]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [PATCH] IDE PIO write Fix #2
Użytkownik Linus Torvalds napisał:
> In article <3CE0D6DE.8090407@evision-ventures.com>,
> Martin Dalecki <dalecki@evision-ventures.com> wrote:
>
>>>--- linux-2.5.15/drivers/ide/ide-taskfile.c.orig Fri May 10 11:49:35 2002
>>>+++ linux-2.5.15/drivers/ide/ide-taskfile.c Tue May 14 10:40:43 2002
>>>@@ -606,7 +606,7 @@
>>> if (!ide_end_request(drive, rq, 1))
>>> return ide_stopped;
>>>
>>>- if ((rq->current_nr_sectors==1) ^ (stat & DRQ_STAT)) {
>>>+ if ((rq->nr_sectors == 1) ^ ((stat & DRQ_STAT) != 0)) {
>>
>
> Well, that's definitely an improvement - the original code makes no
> sense at all, since it's doing a bitwise xor on two bits that are not
> the same, and then uses that as a boolean value.
>
> Your change at least makes it use the bitwise xor on properly logical
> values, making the bitwise xor work as a _logical_ xor.
>
> Although at that point I'd just get rid of the xor, and replace it by
> the "!=" operation - which is equivalent on logical ops.
>
>
>>> pBuf = ide_map_rq(rq, &flags);
>>> DTF("write: %p, rq->current_nr_sectors: %d\n", pBuf, (int) rq->current_nr_sectors);
>>
>>
>>Hmm. There is something else that smells in the above, since the XOR operator
>>doesn't seem to be proper. Why shouldn't we get DRQ_STAT at all on short
>>request? Could you perhaps just try to replace it with an OR?
>
>
> The XOR operation is a valid op, if you just use it on valid values,
> which the patch does seem to make it do.
>
> I don't know whether the logic is _correct_ after that, but at least
> there is some remote chance that it might make sense.
>
> Linus

As far as I can see the patch makes sense. It is just exposing a problem
which was hidden before.

-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/

\
 
 \ /
  Last update: 2005-03-22 13:22    [W:0.136 / U:5.956 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site