linux-kernel - Re: [PATCH v2 03/16] powerpc/watchpoint: Introduce function to get nr watchpoints dynamically

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Message-Id: <b6ff59ce-8251-c50f-1c0e-b1f54fccb09f@linux.ibm.com>
Date:   Wed, 1 Apr 2020 12:20:03 +0530
From:   Ravi Bangoria <ravi.bangoria@...ux.ibm.com>
To:     Christophe Leroy <christophe.leroy@....fr>
Cc:     mpe@...erman.id.au, mikey@...ling.org, apopple@...ux.ibm.com,
        paulus@...ba.org, npiggin@...il.com,
        naveen.n.rao@...ux.vnet.ibm.com, peterz@...radead.org,
        jolsa@...nel.org, oleg@...hat.com, fweisbec@...il.com,
        mingo@...nel.org, linuxppc-dev@...ts.ozlabs.org,
        linux-kernel@...r.kernel.org,
        Ravi Bangoria <ravi.bangoria@...ux.ibm.com>
Subject: Re: [PATCH v2 03/16] powerpc/watchpoint: Introduce function to get nr
 watchpoints dynamically



On 4/1/20 11:59 AM, Christophe Leroy wrote:
> 
> 
> Le 01/04/2020 à 08:12, Ravi Bangoria a écrit :
>> So far we had only one watchpoint, so we have hardcoded HBP_NUM to 1.
>> But future Power architecture is introducing 2nd DAWR and thus kernel
>> should be able to dynamically find actual number of watchpoints
>> supported by hw it's running on. Introduce function for the same.
>> Also convert HBP_NUM macro to HBP_NUM_MAX, which will now represent
>> maximum number of watchpoints supported by Powerpc.
> 
> 
> Everywhere else in the code, it is called 'breakpoint', not 'watchpoint'.
> 
> Wouldn't it be more consistent to call the function nr_bp_slots() instead of nr_wp_slots() ?
> 
> Especially as we are likely going to extend your changes to support DABR2 in addition to DABR on BOOK3S/32.

Sure. I don't have strong onion for nr_wp_slots() and I can rename it to
nr_bp_slots(). but...

Even though existing code uses breakpoint and watchpoint interchangeably,
I'm using wp/watchpoint to represent data-breakpoint, to distinguish it
from instruction-breakpoint (CIABR). So IMHO, nr_wp_slots() should return
number DAWRs/DABRs and nr_bp_slots() should return number of CIABRs. Is
that okay?

Ravi