linux-kernel - Re: [PATCH] irqchip: Use %px to print pointer value

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Message-ID: <CAOiHx=n7yS2dD9LVeQp7p48Sai51aQHjyLHUQMnBvXjwChoh7g@mail.gmail.com>
Date:   Mon, 12 Feb 2018 23:17:47 +0100
From:   Jonas Gorski <jonas.gorski@...il.com>
To:     Marc Zyngier <marc.zyngier@....com>
Cc:     Florian Fainelli <f.fainelli@...il.com>,
        Jaedon Shin <jaedon.shin@...il.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Jason Cooper <jason@...edaemon.net>,
        Kevin Cernekee <cernekee@...il.com>,
        Brian Norris <computersforpeace@...il.com>,
        Gregory Fong <gregory.0xf0@...il.com>,
        bcm-kernel-feedback-list <bcm-kernel-feedback-list@...adcom.com>,
        MIPS Mailing List <linux-mips@...ux-mips.org>,
        linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH] irqchip: Use %px to print pointer value

On 9 February 2018 at 17:04, Marc Zyngier <marc.zyngier@....com> wrote:
> On 09/02/18 15:54, Florian Fainelli wrote:
>> On February 9, 2018 12:51:33 AM PST, Marc Zyngier <marc.zyngier@....com> wrote:
>>> On 09/02/18 02:10, Jaedon Shin wrote:
>>>> Since commit ad67b74d2469 ("printk: hash addresses printed with %p")
>>>> pointers printed with %p are hashed. Use %px instead of %p to print
>>>> pointer value.
>>>>
>>>> Signed-off-by: Jaedon Shin <jaedon.shin@...il.com>
>>>> ---
>>>>  drivers/irqchip/irq-bcm7038-l1.c | 2 +-
>>>>  drivers/irqchip/irq-bcm7120-l2.c | 2 +-
>>>>  drivers/irqchip/irq-brcmstb-l2.c | 2 +-
>>>>  3 files changed, 3 insertions(+), 3 deletions(-)
>>>>
>>>> diff --git a/drivers/irqchip/irq-bcm7038-l1.c
>>> b/drivers/irqchip/irq-bcm7038-l1.c
>>>> index 55cfb986225b..f604c1d89b3b 100644
>>>> --- a/drivers/irqchip/irq-bcm7038-l1.c
>>>> +++ b/drivers/irqchip/irq-bcm7038-l1.c
>>>> @@ -339,7 +339,7 @@ int __init bcm7038_l1_of_init(struct device_node
>>> *dn,
>>>>             goto out_unmap;
>>>>     }
>>>>
>>>> -   pr_info("registered BCM7038 L1 intc (mem: 0x%p, IRQs: %d)\n",
>>>> +   pr_info("registered BCM7038 L1 intc (mem: 0x%px, IRQs: %d)\n",
>>>>             intc->cpus[0]->map_base, IRQS_PER_WORD * intc->n_words);
>>>>
>>>>     return 0;
>>>> diff --git a/drivers/irqchip/irq-bcm7120-l2.c
>>> b/drivers/irqchip/irq-bcm7120-l2.c
>>>> index 983640eba418..1cc4dd1d584a 100644
>>>> --- a/drivers/irqchip/irq-bcm7120-l2.c
>>>> +++ b/drivers/irqchip/irq-bcm7120-l2.c
>>>> @@ -318,7 +318,7 @@ static int __init bcm7120_l2_intc_probe(struct
>>> device_node *dn,
>>>>             }
>>>>     }
>>>>
>>>> -   pr_info("registered %s intc (mem: 0x%p, parent IRQ(s): %d)\n",
>>>> +   pr_info("registered %s intc (mem: 0x%px, parent IRQ(s): %d)\n",
>>>>                     intc_name, data->map_base[0], data->num_parent_irqs);
>>>>
>>>>     return 0;
>>>> diff --git a/drivers/irqchip/irq-brcmstb-l2.c
>>> b/drivers/irqchip/irq-brcmstb-l2.c
>>>> index 691d20eb0bec..6760edeeb666 100644
>>>> --- a/drivers/irqchip/irq-brcmstb-l2.c
>>>> +++ b/drivers/irqchip/irq-brcmstb-l2.c
>>>> @@ -262,7 +262,7 @@ static int __init brcmstb_l2_intc_of_init(struct
>>> device_node *np,
>>>>             ct->chip.irq_set_wake = irq_gc_set_wake;
>>>>     }
>>>>
>>>> -   pr_info("registered L2 intc (mem: 0x%p, parent irq: %d)\n",
>>>> +   pr_info("registered L2 intc (mem: 0x%px, parent irq: %d)\n",
>>>>                     base, parent_irq);
>>>>
>>>>     return 0;
>>>>
>>>
>>> Why is that something useful to do? This just tells you where the
>>> device
>>> is mapped in the VA space, and I doubt that's a useful information,
>>> hashed pointers or not. Am I missing something obvious?
>>
>> No you are right there is not much value in printing the register
>> virtual address (sometimes there is e.g: on MIPS) either we fix the
>> prints to show the physical address of the base register or we could
>> possibly drop the prints entirely.
>
> Displaying the PA can be useful if you have several identical blocks in
> your system and you want to be able to identify them. Given that there
> is probably only one of these controllers per system, the address is
> pretty pointless.

Multiple instances are actually quite common in the STB SoCs, e.g.
bcm7362 has one instance of bcm7038-l1, two instances of bcm7120-l2
and four instances of brcmstb-l2.


Regards
Jonas

P.S: Also What about bcm6345-l1? It also prints it's mapped VAs, not the PAs.