linux-kernel - Re: [PATCH v6 01/11] powerpc/powernv: Data structure and macros definitions

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Message-Id: <87tw62hsc1.fsf@linux.vnet.ibm.com>
Date:   Thu, 06 Apr 2017 18:07:42 +1000
From:   Stewart Smith <stewart@...ux.vnet.ibm.com>
To:     Madhavan Srinivasan <maddy@...ux.vnet.ibm.com>, mpe@...erman.id.au
Cc:     linux-kernel@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org,
        ego@...ux.vnet.ibm.com, bsingharora@...il.com,
        benh@...nel.crashing.org, paulus@...ba.org, anton@...ba.org,
        sukadev@...ux.vnet.ibm.com, mikey@...ling.org, dja@...ens.net,
        eranian@...gle.com, Hemant Kumar <hemant@...ux.vnet.ibm.com>,
        Anju T Sudhakar <anju@...ux.vnet.ibm.com>,
        Madhavan Srinivasan <maddy@...ux.vnet.ibm.com>
Subject: Re: [PATCH v6 01/11] powerpc/powernv: Data structure and macros definitions

Madhavan Srinivasan <maddy@...ux.vnet.ibm.com> writes:

> From: Hemant Kumar <hemant@...ux.vnet.ibm.com>
>
> Create new header file "imc-pmu.h" to add the data structures
> and macros needed for IMC pmu support.
>
> Signed-off-by: Anju T Sudhakar <anju@...ux.vnet.ibm.com>
> Signed-off-by: Hemant Kumar <hemant@...ux.vnet.ibm.com>
> Signed-off-by: Madhavan Srinivasan <maddy@...ux.vnet.ibm.com>
> ---
>  arch/powerpc/include/asm/imc-pmu.h | 68 ++++++++++++++++++++++++++++++++++++++
>  1 file changed, 68 insertions(+)
>  create mode 100644 arch/powerpc/include/asm/imc-pmu.h
>
> diff --git a/arch/powerpc/include/asm/imc-pmu.h b/arch/powerpc/include/asm/imc-pmu.h
> new file mode 100644
> index 000000000000..a3d4f1bf9492
> --- /dev/null
> +++ b/arch/powerpc/include/asm/imc-pmu.h
> @@ -0,0 +1,68 @@
> +#ifndef PPC_POWERNV_IMC_PMU_DEF_H
> +#define PPC_POWERNV_IMC_PMU_DEF_H
> +
> +/*
> + * IMC Nest Performance Monitor counter support.
> + *
> + * Copyright (C) 2016 Madhavan Srinivasan, IBM Corporation.
> + *           (C) 2016 Hemant K Shaw, IBM Corporation.
> + *
> + * This program is free software; you can redistribute it and/or modify it
> + * under the terms of the GNU General Public License version 2 as published
> + * by the Free Software Foundation.
> + */
> +
> +#include <linux/perf_event.h>
> +#include <linux/slab.h>
> +#include <linux/of.h>
> +#include <linux/io.h>
> +#include <asm/opal.h>
> +
> +#define IMC_MAX_CHIPS			32
> +#define IMC_MAX_PMUS			32
> +#define IMC_MAX_PMU_NAME_LEN		256

Why do we need a max length? We get the actual lengths from the device
tree, so we know at each point in time what the length of any new string
should be, right?

Otherwise you appear to be, in the general case, using 10x the memory
than you could.

-- 
Stewart Smith
OPAL Architect, IBM.