linux-kernel - Re: drivers/scsi/st.c:2967: warning: suggest parentheses around operand of '!' or change '|' to '||' or '!' to '~'

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Date:	Tue, 5 May 2009 10:38:10 +0200
From:	Mikael Pettersson <mikpe@...uu.se>
To:	Geert Uytterhoeven <geert@...ux-m68k.org>
Cc:	scsi <linux-scsi@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: drivers/scsi/st.c:2967: warning: suggest parentheses around operand 
	of '!' or change '|' to '||' or '!' to '~'

Geert Uytterhoeven writes:
 > drivers/scsi/st.c:2967: warning: suggest parentheses around operand of
 > '!' or change '|' to '||' or '!' to '~'
 > 
 >         if (cmdstatp->sense_hdr.sense_key == ILLEGAL_REQUEST &&
 >             !(STp->use_pf & PF_TESTED)) {
 >                 /* Try the other possible state of Page Format if not
 >                    already tried */
 >                 STp->use_pf = !STp->use_pf | PF_TESTED;
 >                 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 >                 st_release_request(SRpnt);
 >                 SRpnt = NULL;
 >                 return st_int_ioctl(STp, cmd_in, arg);
 >         }
 > 
 > Looks indeed incorrect to me...

I noticed that too yesterday. I believe the intention is

	STp->use_pf = (!STp->use_pf) | PF_TESTED;

which in this case (PF_TESTED is clear) is the same as

	STp->use_pf = (STp->use_pf ^ USE_PF) | PF_TESTED;

which matches the comment, or

	STp->use_pf ^= (USE_PF | PF_TESTED);

if you want to micro-optimize.
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