linux-kernel - Re: [PATCH] rtc: sunplus: fix format string for printing resource

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Message-Id: <589415b2-ddf2-44e5-bca5-5971f8ab9576@app.fastmail.com>
Date:   Tue, 17 Jan 2023 20:36:57 +0100
From:   "Arnd Bergmann" <arnd@...db.de>
To:     "Randy Dunlap" <rdunlap@...radead.org>,
        "Alexandre Belloni" <alexandre.belloni@...tlin.com>,
        "Arnd Bergmann" <arnd@...nel.org>
Cc:     "Vincent Shih" <vincent.sunplus@...il.com>,
        "Alessandro Zummo" <a.zummo@...ertech.it>,
        linux-rtc@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] rtc: sunplus: fix format string for printing resource

On Tue, Jan 17, 2023, at 19:24, Randy Dunlap wrote:
> On 1/17/23 09:55, Alexandre Belloni wrote:
>> On 17/01/2023 18:24:44+0100, Arnd Bergmann wrote:
>>> From: Arnd Bergmann <arnd@...db.de>
>>>
>>> On 32-bit architectures with 64-bit resource_size_t, sp_rtc_probe()
>>> causes a compiler warning:
>>>
>>> drivers/rtc/rtc-sunplus.c: In function 'sp_rtc_probe':
>>> drivers/rtc/rtc-sunplus.c:243:33: error: format '%x' expects argument of type 'unsigned int', but argument 4 has type 'resource_size_t' {aka 'long long unsigned int'} [-Werror=format=]
>>>   243 |         dev_dbg(&plat_dev->dev, "res = 0x%x, reg_base = 0x%lx\n",
>>>       |                                 ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>>>
>>> The best way to print a resource is the special %pR format string,
>>> and similarly to print a pointer we can use %p and avoid the cast.
>>>
>> 
>> I got this one this morning, which one is more correct? :)
>> https://lore.kernel.org/all/20230117054232.24023-1-rdunlap@infradead.org/

Both are equally correct, it's just a preference.

> I prefer my handling of res->start and Arnd's no-cast handling of reg_base.
> IMO using "%pR" prints too much info, but that's more up to the file's author
> or maintainer...

Right, I could have equally well picked the %pap version, and just
went for brevity in the source. It's only pr_debug(), so very few
users are going to actually see the output.

     Arnd